pureboot: review-pass fixes to the host tool and device runner

pureboot.py: reject an empty image file with a clear error instead of
an IndexError deep in the vector-surgery planner; tighten the erase
docstring (order is irrelevant there — every target byte is the same
value, unlike a real flash where page 0 must go last).

pureboot_device.c: the GPIO bridge's bit_cycles used plain truncating
division where the firmware computes its own bit period with
round-to-nearest (uart.hpp: (Clock.hz + Baud.bd/2)/Baud.bd) — one
cycle off per bit on both tinies, harmless in practice but needless
drift against a firmware built to a different constant. Matched
exactly. Also clear the queued-bytes/decode-in-progress bridge state
on the test-only reset signal, so a future reset-mid-transfer scenario
can't feed a freshly reset chip bytes queued for its previous life.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AReSwkWkPX2A9Ym6grxRAh

.clang-format

@@ -1,5 +1,6 @@
 ---
 BasedOnStyle: LLVM
+Standard: Latest
 ColumnLimit: 120
 IndentWidth: 4
 TabWidth: 4

.gitignore

@@ -9,3 +9,12 @@ Debug
 *.eeprom
 *.lss
 *.map
+
+# CMake / clangd
+/build/
+compile_commands.json
+.cache/
+
+# Python
+__pycache__/
+*.pyc

.gitmodules

@@ -1,27 +0,0 @@
-[submodule "tsb/io"]
-	path = tsb/io
-	url = git@git.blackmark.me:avr/io.git
-[submodule "tsb/flash"]
-	path = tsb/flash
-	url = git@git.blackmark.me:avr/flash.git
-[submodule "tsb/uart"]
-	path = tsb/uart
-	url = git@git.blackmark.me:avr/uart.git
-[submodule "tsb/type"]
-	path = tsb/type
-	url = git@git.blackmark.me:avr/type.git
-[submodule "stk500v2/type"]
-	path = stk500v2/type
-	url = git@git.blackmark.me:avr/type.git
-[submodule "stk500v2/io"]
-	path = stk500v2/io
-	url = git@git.blackmark.me:avr/io.git
-[submodule "stk500v2/uart"]
-	path = stk500v2/uart
-	url = git@git.blackmark.me:avr/uart.git
-[submodule "stk500v2/flash"]
-	path = stk500v2/flash
-	url = git@git.blackmark.me:avr/flash.git
-[submodule "blink/io"]
-	path = blink/io
-	url = git@git.blackmark.me:avr/io.git

CMakeLists.txt

@@ -0,0 +1,177 @@
+cmake_minimum_required(VERSION 3.28)
+
+project(tsb_libavr LANGUAGES CXX)
+
+# libavr from a local checkout (LIBAVR_ROOT) or the forge; the toolchain file
+# comes from the same checkout via CMakePresets.json.
+include(FetchContent)
+if(NOT LIBAVR_ROOT AND DEFINED ENV{LIBAVR_ROOT})
+	set(LIBAVR_ROOT $ENV{LIBAVR_ROOT})
+endif()
+if(LIBAVR_ROOT)
+	FetchContent_Declare(libavr SOURCE_DIR ${LIBAVR_ROOT})
+else()
+	FetchContent_Declare(libavr GIT_REPOSITORY git@git.blackmark.me:avr/libavr.git GIT_TAG main)
+endif()
+FetchContent_MakeAvailable(libavr)
+
+if(PROJECT_IS_TOP_LEVEL)
+	add_compile_options(-Werror) # warnings are errors for the port's own code
+	enable_testing()
+
+	# The behavioral tests drive the real wire protocols over a simavr pty
+	# (as the host tools do) and actually flash the device. The runners are
+	# host programs built at configure time against libsimavr; if they or
+	# Python are missing, only the size tests run.
+	find_program(_host_cc NAMES cc gcc)
+	find_package(Python3 COMPONENTS Interpreter)
+	if(_host_cc AND Python3_FOUND)
+		set(PB_DEVICE ${CMAKE_BINARY_DIR}/pureboot_device)
+		execute_process(
+		    COMMAND ${_host_cc} -O2 -I/usr/include/simavr -I/usr/include/simavr/parts
+		            -o ${PB_DEVICE} ${CMAKE_CURRENT_SOURCE_DIR}/test/pureboot_device.c
+		            -lsimavr -lsimavrparts -lelf -lutil
+		    RESULT_VARIABLE _pbdev_res ERROR_VARIABLE _pbdev_err)
+		if(NOT _pbdev_res EQUAL 0)
+			message(STATUS "pureboot_device not built (${_pbdev_err}) — protocol tests skipped")
+			unset(PB_DEVICE)
+		endif()
+		if(LIBAVR_MCU STREQUAL "atmega328p")
+			set(TSB_DEVICE ${CMAKE_BINARY_DIR}/tsb_device)
+			execute_process(
+			    COMMAND ${_host_cc} -O2 -I/usr/include/simavr -I/usr/include/simavr/parts
+			            -o ${TSB_DEVICE} ${CMAKE_CURRENT_SOURCE_DIR}/test/device.c
+			            -lsimavr -lsimavrparts -lelf
+			    RESULT_VARIABLE _dev_res ERROR_VARIABLE _dev_err)
+			if(NOT _dev_res EQUAL 0)
+				message(STATUS "tsb_device not built (${_dev_err}) — protocol tests skipped")
+				unset(TSB_DEVICE)
+			endif()
+		endif()
+	endif()
+endif()
+
+# The TinySafeBoot protocol reimplemented on libavr in three variants that trade
+# clarity for size. Each links into the ATmega328P boot section (BOOTSZ selects
+# its size; BOOTRST vectors a reset to its base) with -nostartfiles — a polled
+# loader has no use for the crt or the vector table. The naked entry sits in
+# .vectors, laid first, and runs. The boot base is FLASHEND+1 minus the section
+# size; the linker section-start and the source's boot_bytes agree. tsb_app is
+# the application's reset vector, pinned to 0 here so the loaders jump to a
+# named function; --pmem-wrap-around lets relaxation turn that absolute jump
+# into the wrapped rjmp AVR's modulo-flash PC actually executes.
+# All three implement the full oracle feature set (see oracle/README.md):
+# watchdog bail, one-wire half-duplex, config-page activation timeout, password
+# gate, emergency erase, config/flash/EEPROM read-write. They differ only in how,
+# and the size gradient is the cost of that "how" — see dev/lessons.md.
+#   tsb_asm   — the tricks tier's C++ with exactly two routines in asm (the
+#                 bounded rx and the page-store loop — the two whose remaining
+#                 cost is the C ABI itself): 510 B in the 512 B section the
+#                 hand-written 500 B oracle occupies. Everything else, from
+#                 bring-up to dispatch, is C++ on libavr.
+#   tsb_tricks — no asm at all: the whole-loader register allocation lives in
+#                 global register variables (Y walks the page pointer), every
+#                 helper is a tiny noinline primitive placed by the
+#                 global-register store rules, pages stream straight to
+#                 SPM/EEPROM, and the bring-up is the two reset-non-default
+#                 registers only. 526 B in the 1 KB section (BOOTSZ=10) — 14
+#                 over the oracle's section, from 168 over at this tier's first
+#                 floor.
+#   tsb_pure  — pure idiomatic libavr, one function per command, TU-local
+#                 (internal linkage), streaming (no SRAM page buffer): 836 B in
+#                 the 1 KB section.
+#
+# add_tsb_variant(<name> <boot-section-bytes>)
+function(add_tsb_variant name bytes)
+	math(EXPR base_dec "32768 - ${bytes}")
+	math(EXPR base_hex "${base_dec}" OUTPUT_FORMAT HEXADECIMAL)
+	add_executable(${name} tsb/${name}.cpp)
+	target_link_libraries(${name} PRIVATE libavr)
+	target_link_options(${name} PRIVATE -nostartfiles -Wl,--section-start=.text=${base_hex}
+	                    -Wl,--defsym=tsb_app=0 -Wl,--pmem-wrap-around=32k)
+	add_custom_command(TARGET ${name} POST_BUILD COMMAND ${CMAKE_SIZE} $<TARGET_FILE:${name}>)
+	if(PROJECT_IS_TOP_LEVEL)
+		add_test(NAME ${name}.size
+		         COMMAND ${CMAKE_COMMAND} -DSIZE_TOOL=${CMAKE_SIZE} -DELF=$<TARGET_FILE:${name}>
+		                 -DLIMIT=${bytes} -P ${CMAKE_CURRENT_SOURCE_DIR}/test/check_size.cmake)
+		if(DEFINED TSB_DEVICE)
+			add_test(NAME ${name}.protocol
+			         COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/tsbtest.py
+			                 ${TSB_DEVICE} $<TARGET_FILE:${name}> ${base_hex})
+		endif()
+	endif()
+endfunction()
+
+# The tsb tiers reimplement the ATmega328P-only reference protocol; the other
+# chips build pureboot alone.
+if(LIBAVR_MCU STREQUAL "atmega328p")
+	add_tsb_variant(tsb_asm 512)
+	add_tsb_variant(tsb_pure 1024)
+	add_tsb_variant(tsb_tricks 1024)
+endif()
+
+# pureboot — the pure-constraint port (see pureboot/README.md): one source,
+# no inline assembly, no global register variables, every libavr chip, 512
+# bytes each. The loader owns the top 512 bytes of flash on every chip; the
+# application entry symbol is address 0 on the mega (reset re-vectors to the
+# loader through BOOTRST, so word 0 stays the application's own vector) and
+# the trampoline word just below the loader on the tinies (host-side vector
+# surgery points it at the application). --pmem-wrap-around models AVR's
+# modulo-flash PC where the flash is big enough to need it.
+if(LIBAVR_MCU STREQUAL "attiny13a")
+	set(_pb_flash 1024)
+	set(_pb_wrap "")
+	set(_pb_page 32)
+	set(_pb_hz 9600000)
+	set(_pb_baud 57600)
+	set(_pb_eeprom 64)
+elseif(LIBAVR_MCU STREQUAL "attiny85")
+	set(_pb_flash 8192)
+	set(_pb_wrap -Wl,--pmem-wrap-around=8k)
+	set(_pb_page 64)
+	set(_pb_hz 8000000)
+	set(_pb_baud 57600)
+	set(_pb_eeprom 512)
+else()
+	set(_pb_flash 32768)
+	set(_pb_wrap -Wl,--pmem-wrap-around=32k)
+	set(_pb_page 128)
+	set(_pb_hz 16000000)
+	set(_pb_baud 115200)
+	set(_pb_eeprom 1024)
+endif()
+math(EXPR _pb_base "${_pb_flash} - 512")
+math(EXPR _pb_base_hex "${_pb_base}" OUTPUT_FORMAT HEXADECIMAL)
+if(LIBAVR_MCU STREQUAL "atmega328p")
+	set(_pb_app 0)
+else()
+	math(EXPR _pb_app "${_pb_base} - 2")
+endif()
+
+add_executable(pureboot pureboot/pureboot.cpp)
+target_link_libraries(pureboot PRIVATE libavr)
+target_link_options(pureboot PRIVATE -nostartfiles -Wl,--section-start=.text=${_pb_base_hex}
+                    -Wl,--defsym=pureboot_app=${_pb_app} ${_pb_wrap})
+add_custom_command(TARGET pureboot POST_BUILD COMMAND ${CMAKE_SIZE} $<TARGET_FILE:pureboot>)
+if(PROJECT_IS_TOP_LEVEL)
+	add_test(NAME pureboot.size
+	         COMMAND ${CMAKE_COMMAND} -DSIZE_TOOL=${CMAKE_SIZE} -DELF=$<TARGET_FILE:pureboot>
+	                 -DLIMIT=512 -P ${CMAKE_CURRENT_SOURCE_DIR}/test/check_size.cmake)
+
+	# The protocol test flashes this fixture through the loader with the real
+	# host tool and expects its banner after the hand-over; a normally linked
+	# application whose reset vector is what the tinies' surgery re-homes.
+	if(DEFINED PB_DEVICE)
+		add_executable(pbapp test/pbapp.cpp)
+		target_link_libraries(pbapp PRIVATE libavr)
+		add_custom_command(TARGET pbapp POST_BUILD
+		                   COMMAND ${CMAKE_OBJCOPY} -O binary $<TARGET_FILE:pbapp> $<TARGET_FILE:pbapp>.bin)
+		add_test(NAME pureboot.protocol
+		         COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/pbtest.py
+		                 ${PB_DEVICE} $<TARGET_FILE:pureboot> ${LIBAVR_MCU} ${_pb_hz} ${_pb_base_hex}
+		                 ${_pb_page} ${_pb_baud} ${_pb_eeprom} $<TARGET_FILE:pbapp>.bin
+		                 ${CMAKE_CURRENT_SOURCE_DIR}/pureboot/pureboot.py
+		                 ${CMAKE_BINARY_DIR}/pbtest-work)
+		set_tests_properties(pureboot.protocol PROPERTIES TIMEOUT 180)
+	endif()
+endif()

CMakePresets.json

@@ -0,0 +1,86 @@
+{
+	"version": 8,
+	"configurePresets": [
+		{
+			"name": "base",
+			"hidden": true,
+			"generator": "Ninja",
+			"binaryDir": "${sourceDir}/build/${presetName}",
+			"toolchainFile": "$env{LIBAVR_ROOT}/cmake/avr-toolchain.cmake",
+			"cacheVariables": {
+				"CMAKE_BUILD_TYPE": "Release",
+				"CMAKE_EXPORT_COMPILE_COMMANDS": "ON",
+				"CMAKE_COLOR_DIAGNOSTICS": "ON"
+			}
+		},
+		{
+			"name": "atmega328p-generated",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "atmega328p", "LIBAVR_REFLECT": "OFF" }
+		},
+		{
+			"name": "atmega328p-reflect",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "atmega328p", "LIBAVR_REFLECT": "ON" }
+		},
+		{
+			"name": "attiny85-generated",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "attiny85", "LIBAVR_REFLECT": "OFF" }
+		},
+		{
+			"name": "attiny85-reflect",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "attiny85", "LIBAVR_REFLECT": "ON" }
+		},
+		{
+			"name": "attiny13a-generated",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "attiny13a", "LIBAVR_REFLECT": "OFF" }
+		},
+		{
+			"name": "attiny13a-reflect",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "attiny13a", "LIBAVR_REFLECT": "ON" }
+		}
+	],
+	"buildPresets": [
+		{ "name": "atmega328p-generated", "configurePreset": "atmega328p-generated" },
+		{ "name": "atmega328p-reflect", "configurePreset": "atmega328p-reflect" },
+		{ "name": "attiny85-generated", "configurePreset": "attiny85-generated" },
+		{ "name": "attiny85-reflect", "configurePreset": "attiny85-reflect" },
+		{ "name": "attiny13a-generated", "configurePreset": "attiny13a-generated" },
+		{ "name": "attiny13a-reflect", "configurePreset": "attiny13a-reflect" }
+	],
+	"workflowPresets": [
+		{
+			"name": "atmega328p-generated",
+			"steps": [
+				{ "type": "configure", "name": "atmega328p-generated" },
+				{ "type": "build", "name": "atmega328p-generated" },
+				{ "type": "test", "name": "atmega328p-generated" }
+			]
+		},
+		{
+			"name": "attiny85-generated",
+			"steps": [
+				{ "type": "configure", "name": "attiny85-generated" },
+				{ "type": "build", "name": "attiny85-generated" },
+				{ "type": "test", "name": "attiny85-generated" }
+			]
+		},
+		{
+			"name": "attiny13a-generated",
+			"steps": [
+				{ "type": "configure", "name": "attiny13a-generated" },
+				{ "type": "build", "name": "attiny13a-generated" },
+				{ "type": "test", "name": "attiny13a-generated" }
+			]
+		}
+	],
+	"testPresets": [
+		{ "name": "atmega328p-generated", "configurePreset": "atmega328p-generated", "output": { "outputOnFailure": true } },
+		{ "name": "attiny85-generated", "configurePreset": "attiny85-generated", "output": { "outputOnFailure": true } },
+		{ "name": "attiny13a-generated", "configurePreset": "attiny13a-generated", "output": { "outputOnFailure": true } }
+	]
+}

blink/blink.cppproj

@@ -1,239 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="14.0">
-  <PropertyGroup>
-    <SchemaVersion>2.0</SchemaVersion>
-    <ProjectVersion>7.0</ProjectVersion>
-    <ToolchainName>com.Atmel.AVRGCC8.CPP</ToolchainName>
-    <ProjectGuid>{d887fc8e-ee68-4248-8382-92dbc9a54145}</ProjectGuid>
-    <avrdevice>ATmega328P</avrdevice>
-    <avrdeviceseries>none</avrdeviceseries>
-    <OutputType>Executable</OutputType>
-    <Language>CPP</Language>
-    <OutputFileName>$(MSBuildProjectName)</OutputFileName>
-    <OutputFileExtension>.elf</OutputFileExtension>
-    <OutputDirectory>$(MSBuildProjectDirectory)\$(Configuration)</OutputDirectory>
-    <AssemblyName>blink</AssemblyName>
-    <Name>blink</Name>
-    <RootNamespace>blink</RootNamespace>
-    <ToolchainFlavour>avr-g++-9.1.0</ToolchainFlavour>
-    <KeepTimersRunning>true</KeepTimersRunning>
-    <OverrideVtor>false</OverrideVtor>
-    <CacheFlash>true</CacheFlash>
-    <ProgFlashFromRam>true</ProgFlashFromRam>
-    <RamSnippetAddress>0x20000000</RamSnippetAddress>
-    <UncachedRange />
-    <preserveEEPROM>true</preserveEEPROM>
-    <OverrideVtorValue>exception_table</OverrideVtorValue>
-    <BootSegment>2</BootSegment>
-    <ResetRule>0</ResetRule>
-    <eraseonlaunchrule>0</eraseonlaunchrule>
-    <EraseKey />
-    <avrtool>com.atmel.avrdbg.tool.atmelice</avrtool>
-    <avrtoolserialnumber>J41800099437</avrtoolserialnumber>
-    <avrdeviceexpectedsignature>0x1E950F</avrdeviceexpectedsignature>
-    <com_atmel_avrdbg_tool_stk500>
-      <ToolOptions>
-        <InterfaceProperties>
-          <IspClock>125000</IspClock>
-        </InterfaceProperties>
-        <InterfaceName>ISP</InterfaceName>
-      </ToolOptions>
-      <ToolType>com.atmel.avrdbg.tool.stk500</ToolType>
-      <ToolNumber>
-      </ToolNumber>
-      <ToolName>STK500</ToolName>
-    </com_atmel_avrdbg_tool_stk500>
-    <avrtoolinterface>ISP</avrtoolinterface>
-    <avrtoolinterfaceclock>125000</avrtoolinterfaceclock>
-    <AsfFrameworkConfig>
-      <framework-data xmlns="">
-        <options />
-        <configurations />
-        <files />
-        <documentation help="" />
-        <offline-documentation help="" />
-        <dependencies>
-          <content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.47.0" />
-        </dependencies>
-      </framework-data>
-    </AsfFrameworkConfig>
-    <com_atmel_avrdbg_tool_atmelice>
-      <ToolOptions>
-        <InterfaceProperties>
-          <IspClock>125000</IspClock>
-        </InterfaceProperties>
-        <InterfaceName>ISP</InterfaceName>
-      </ToolOptions>
-      <ToolType>com.atmel.avrdbg.tool.atmelice</ToolType>
-      <ToolNumber>J41800099437</ToolNumber>
-      <ToolName>Atmel-ICE</ToolName>
-    </com_atmel_avrdbg_tool_atmelice>
-    <custom>
-      <ToolOptions>
-        <InterfaceProperties>
-          <IspClock>125000</IspClock>
-        </InterfaceProperties>
-        <InterfaceName>
-        </InterfaceName>
-      </ToolOptions>
-      <ToolType>custom</ToolType>
-      <ToolNumber>
-      </ToolNumber>
-      <ToolName>Custom Programming Tool</ToolName>
-    </custom>
-    <com_atmel_avrdbg_tool_simulator>
-      <ToolOptions xmlns="">
-        <InterfaceProperties>
-        </InterfaceProperties>
-        <InterfaceName>
-        </InterfaceName>
-      </ToolOptions>
-      <ToolType xmlns="">com.atmel.avrdbg.tool.simulator</ToolType>
-      <ToolNumber xmlns="">
-      </ToolNumber>
-      <ToolName xmlns="">Simulator</ToolName>
-    </com_atmel_avrdbg_tool_simulator>
-    <AAFDebugger>
-      <AAFDebugFiles>
-      </AAFDebugFiles>
-    </AAFDebugger>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
-    <ToolchainSettings>
-      <AvrGccCpp>
-        <avrgcc.common.Device>-mmcu=atmega328p</avrgcc.common.Device>
-        <avrgcc.common.outputfiles.hex>True</avrgcc.common.outputfiles.hex>
-        <avrgcc.common.outputfiles.lss>True</avrgcc.common.outputfiles.lss>
-        <avrgcc.common.outputfiles.eep>True</avrgcc.common.outputfiles.eep>
-        <avrgcc.common.outputfiles.srec>True</avrgcc.common.outputfiles.srec>
-        <avrgcc.common.outputfiles.usersignatures>False</avrgcc.common.outputfiles.usersignatures>
-        <avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcc.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>NDEBUG</Value>
-          </ListValues>
-        </avrgcc.compiler.symbols.DefSymbols>
-        <avrgcc.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcc.compiler.directories.IncludePaths>
-        <avrgcc.compiler.optimization.level>Optimize for size (-Os)</avrgcc.compiler.optimization.level>
-        <avrgcc.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcc.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcc.compiler.warnings.AllWarnings>True</avrgcc.compiler.warnings.AllWarnings>
-        <avrgcc.compiler.warnings.ExtraWarnings>True</avrgcc.compiler.warnings.ExtraWarnings>
-        <avrgcc.compiler.warnings.Pedantic>True</avrgcc.compiler.warnings.Pedantic>
-        <avrgcc.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -std=c11</avrgcc.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcccpp.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>NDEBUG</Value>
-          </ListValues>
-        </avrgcccpp.compiler.symbols.DefSymbols>
-        <avrgcccpp.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.compiler.directories.IncludePaths>
-        <avrgcccpp.compiler.optimization.level>Optimize for size (-Os)</avrgcccpp.compiler.optimization.level>
-        <avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcccpp.compiler.warnings.AllWarnings>True</avrgcccpp.compiler.warnings.AllWarnings>
-        <avrgcccpp.compiler.warnings.Pedantic>True</avrgcccpp.compiler.warnings.Pedantic>
-        <avrgcccpp.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -Wextra -std=c++17</avrgcccpp.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.linker.libraries.Libraries>
-          <ListValues>
-            <Value>libm</Value>
-          </ListValues>
-        </avrgcccpp.linker.libraries.Libraries>
-        <avrgcccpp.assembler.general.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.assembler.general.IncludePaths>
-      </AvrGccCpp>
-    </ToolchainSettings>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
-    <ToolchainSettings>
-      <AvrGccCpp>
-        <avrgcc.common.Device>-mmcu=atmega328p</avrgcc.common.Device>
-        <avrgcc.common.outputfiles.hex>True</avrgcc.common.outputfiles.hex>
-        <avrgcc.common.outputfiles.lss>True</avrgcc.common.outputfiles.lss>
-        <avrgcc.common.outputfiles.eep>True</avrgcc.common.outputfiles.eep>
-        <avrgcc.common.outputfiles.srec>True</avrgcc.common.outputfiles.srec>
-        <avrgcc.common.outputfiles.usersignatures>False</avrgcc.common.outputfiles.usersignatures>
-        <avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcc.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>DEBUG</Value>
-          </ListValues>
-        </avrgcc.compiler.symbols.DefSymbols>
-        <avrgcc.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcc.compiler.directories.IncludePaths>
-        <avrgcc.compiler.optimization.level>Optimize (-O1)</avrgcc.compiler.optimization.level>
-        <avrgcc.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcc.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcc.compiler.optimization.DebugLevel>Maximum (-g3)</avrgcc.compiler.optimization.DebugLevel>
-        <avrgcc.compiler.warnings.AllWarnings>True</avrgcc.compiler.warnings.AllWarnings>
-        <avrgcc.compiler.warnings.ExtraWarnings>True</avrgcc.compiler.warnings.ExtraWarnings>
-        <avrgcc.compiler.warnings.Pedantic>True</avrgcc.compiler.warnings.Pedantic>
-        <avrgcc.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -std=c11</avrgcc.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcccpp.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>DEBUG</Value>
-          </ListValues>
-        </avrgcccpp.compiler.symbols.DefSymbols>
-        <avrgcccpp.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.compiler.directories.IncludePaths>
-        <avrgcccpp.compiler.optimization.level>Optimize (-O1)</avrgcccpp.compiler.optimization.level>
-        <avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcccpp.compiler.optimization.DebugLevel>Maximum (-g3)</avrgcccpp.compiler.optimization.DebugLevel>
-        <avrgcccpp.compiler.warnings.AllWarnings>True</avrgcccpp.compiler.warnings.AllWarnings>
-        <avrgcccpp.compiler.warnings.Pedantic>True</avrgcccpp.compiler.warnings.Pedantic>
-        <avrgcccpp.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -Wextra -std=c++17</avrgcccpp.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.linker.libraries.Libraries>
-          <ListValues>
-            <Value>libm</Value>
-          </ListValues>
-        </avrgcccpp.linker.libraries.Libraries>
-        <avrgcccpp.assembler.general.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.assembler.general.IncludePaths>
-        <avrgcccpp.assembler.debugging.DebugLevel>Default (-Wa,-g)</avrgcccpp.assembler.debugging.DebugLevel>
-      </AvrGccCpp>
-    </ToolchainSettings>
-  </PropertyGroup>
-  <ItemGroup>
-    <Compile Include="bootloader.cpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="bootloader.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="clock.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="io\io.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="main.cpp">
-      <SubType>compile</SubType>
-    </Compile>
-  </ItemGroup>
-  <ItemGroup>
-    <Folder Include="io" />
-  </ItemGroup>
-  <Import Project="$(AVRSTUDIO_EXE_PATH)\\Vs\\Compiler.targets" />
-</Project>

blink/bootloader.cpp

@@ -1,46 +0,0 @@
-#include "bootloader.hpp"
-
-#include <avr/io.h>
-#include <avr/pgmspace.h>
-#include <avr/wdt.h>
-
-namespace {
-
-typedef void (*jmp_fn)() __attribute__((noreturn));
-
-jmp_fn boot = reinterpret_cast<jmp_fn>(0x0000);
-jmp_fn bootloader = reinterpret_cast<jmp_fn>(0x7800 / 2);
-
-} // namespace
-
-bool Bootloader::handleReset()
-{
-	wdt_reset();
-	uint8_t mcuStatus = MCUSR;
-	MCUSR &= ~(1 << WDRF);
-	wdt_disable();
-	return (mcuStatus & (1 << WDRF));
-}
-
-void Bootloader::reset()
-{
-	wdt_enable(WDTO_15MS);
-	while (true)
-		;
-}
-
-bool Bootloader::check()
-{
-	if (pgm_read_byte(reinterpret_cast<uint16_t>(bootloader) * 2) != 0xFF)
-		return true;
-
-	return false;
-}
-
-void Bootloader::call()
-{
-	if (check())
-		bootloader();
-	else
-		boot();
-}

blink/bootloader.hpp

@@ -1,24 +0,0 @@
-#pragma once
-
-class Bootloader {
-  public:
-	template <typename Fn>
-	static inline void init(Fn callback)
-	{
-		if (handleReset()) {
-			callback();
-			call();
-		}
-	}
-
-	static inline void enter()
-	{
-		reset();
-	}
-
-  private:
-	static bool handleReset();
-	static void reset();
-	static bool check();
-	static void call();
-};

blink/clock.hpp

@@ -1,5 +0,0 @@
-#pragma once
-
-//#define F_CPU 18'432'000
-#define F_CPU 16'000'000
-#include <util/delay.h>

blink/main.cpp

@@ -1,30 +0,0 @@
-#include "clock.hpp"
-
-#include "io/io.hpp"
-
-#include "bootloader.hpp"
-
-int main()
-{
-	io::Pin<io::P::B5> ledPin;
-	ledPin.dir(io::Dir::OUT);
-	ledPin = false;
-
-	Bootloader::init([&ledPin]() {
-		for (uint8_t i = 0; i < 10; ++i) {
-			ledPin = true;
-			_delay_ms(50);
-			ledPin = false;
-			_delay_ms(50);
-		}
-	});
-
-	for (uint8_t i = 0; i < 10; ++i) {
-		ledPin.toggle();
-		_delay_ms(1000);
-	}
-
-	Bootloader::enter();
-
-	return 0;
-}

bootloader.atsln

@@ -1,34 +0,0 @@
-
-Microsoft Visual Studio Solution File, Format Version 12.00
-# Atmel Studio Solution File, Format Version 11.00
-VisualStudioVersion = 14.0.23107.0
-MinimumVisualStudioVersion = 10.0.40219.1
-Project("{E66E83B9-2572-4076-B26E-6BE79FF3018A}") = "tsb", "tsb\tsb.cppproj", "{DCE6C7E3-EE26-4D79-826B-08594B9AD897}"
-EndProject
-Project("{E66E83B9-2572-4076-B26E-6BE79FF3018A}") = "stk500v2", "stk500v2\stk500v2.cppproj", "{19798CCE-5D96-40E9-B769-D209715DCE0C}"
-EndProject
-Project("{E66E83B9-2572-4076-B26E-6BE79FF3018A}") = "blink", "blink\blink.cppproj", "{D887FC8E-EE68-4248-8382-92DBC9A54145}"
-EndProject
-Global
-	GlobalSection(SolutionConfigurationPlatforms) = preSolution
-		Debug|AVR = Debug|AVR
-		Release|AVR = Release|AVR
-	EndGlobalSection
-	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{DCE6C7E3-EE26-4D79-826B-08594B9AD897}.Debug|AVR.ActiveCfg = Debug|AVR
-		{DCE6C7E3-EE26-4D79-826B-08594B9AD897}.Debug|AVR.Build.0 = Debug|AVR
-		{DCE6C7E3-EE26-4D79-826B-08594B9AD897}.Release|AVR.ActiveCfg = Release|AVR
-		{DCE6C7E3-EE26-4D79-826B-08594B9AD897}.Release|AVR.Build.0 = Release|AVR
-		{19798CCE-5D96-40E9-B769-D209715DCE0C}.Debug|AVR.ActiveCfg = Debug|AVR
-		{19798CCE-5D96-40E9-B769-D209715DCE0C}.Debug|AVR.Build.0 = Debug|AVR
-		{19798CCE-5D96-40E9-B769-D209715DCE0C}.Release|AVR.ActiveCfg = Release|AVR
-		{19798CCE-5D96-40E9-B769-D209715DCE0C}.Release|AVR.Build.0 = Release|AVR
-		{D887FC8E-EE68-4248-8382-92DBC9A54145}.Debug|AVR.ActiveCfg = Debug|AVR
-		{D887FC8E-EE68-4248-8382-92DBC9A54145}.Debug|AVR.Build.0 = Debug|AVR
-		{D887FC8E-EE68-4248-8382-92DBC9A54145}.Release|AVR.ActiveCfg = Release|AVR
-		{D887FC8E-EE68-4248-8382-92DBC9A54145}.Release|AVR.Build.0 = Release|AVR
-	EndGlobalSection
-	GlobalSection(SolutionProperties) = preSolution
-		HideSolutionNode = FALSE
-	EndGlobalSection
-EndGlobal

oracle/README.md

@@ -0,0 +1,49 @@
+# Oracle — the hand-written TinySafeBoot assembly
+
+`tsb-fixedbaud.asm` is the reference implementation this port is measured
+against: the **native-UART, fixed-baud** TinySafeBoot bootloader, hand-written
+in AVR assembly. It is the size-and-feature bar for the port's `tsb_asm` tier.
+
+- **Source**: <https://github.com/seedrobotics/tinysafeboot>
+  (`firmware_ASM/latest_stable_release/20200727-fixedbaud/main.asm`), the Seed
+  Robotics fixed-baud fork of Julien Thomas' TinySafeBoot.
+- **License**: GPLv3 (see the header in the file). It is vendored here **only as
+  a reference oracle** — it is not compiled, linked, or distributed as part of
+  the MIT-licensed port. Mere aggregation.
+
+## Why this variant
+
+The user chose the fixed-baud, hardware-UART variant deliberately: it is the one
+whose feature set the port must match. It fits the **complete** TSB feature set
+into the 512-byte ATmega boot section:
+
+| Feature | Oracle routine |
+|---|---|
+| Watchdog-reset bail straight to the app | `RESET` (WDRF check) |
+| One-wire half-duplex (RX/TX shorted): RXEN/TXEN toggled per direction, TX turnaround guard | `SetRX` / `SetTX` / `TransmitByte` |
+| Activation timeout read from the config page, with a lockout-proof minimum | `WRX1To` (uses `utimeoutH`) |
+| 3×`@` activation knock | `ActCharRcvd` |
+| Password gate; wrong byte hangs (still draining the UART) | `CheckPassword` |
+| Emergency erase on password `\0` + double-confirm — wipes flash, EEPROM and the config page | `EmergencyErase` |
+| Device-info block (16 bytes) | `SendDeviceInfo` / `DEVICEINFO` |
+| App-flash read/write (`f`/`F`), EEPROM read/write (`e`/`E`), config read/write (`c`/`C`) | `CheckCommands` |
+
+## Assembled size (the bar)
+
+Assembled for the ATmega328P with `avra`:
+
+```
+avra -I /usr/share/avra tsb-fixedbaud.asm   # after uncommenting .include "m328Pdef.inc"
+#   Code : 250 words (500 bytes)  — the whole loader, all features, in the 512 B section
+```
+
+**500 bytes with every feature** — the proof that ≤512 B and full feature parity
+are simultaneously reachable. The port's `tsb_asm` tier meets the same bar at
+510 B in the same 512 B section, written in C++ on libavr except the two
+routines whose remaining cost is the calling convention itself (the bounded rx
+and the page-store loop); `tsb_tricks` needs no assembly at all at 526 B, and
+`tsb_pure` stays fully idiomatic at 836 B, both in the 1 KB section.
+
+The oracle targets 20 MHz / 33333 baud; the port targets 16 MHz / 115200 baud
+(what the simavr protocol test drives). Baud and geometry differ, code size and
+feature set do not.

oracle/tsb-fixedbaud.asm

@@ -0,0 +1,776 @@
+;***********************************************************************
+;***********************************************************************
+;***********************************************************************
+; TinySafeBoot - The Universal Bootloader for AVR ATmegas
+;***********************************************************************
+;***********************************************************************
+;***********************************************************************
+;
+;-----------------------------------------------------------------------
+; 2020 - Version using native UART, Fixed Baud by Seed Robotics in 2020 
+;-----------------------------------------------------------------------
+; meant for use on ATMEGA devices only (with native UART - UART0)
+;
+; Main differences to Regular TSB Bootloader:
+; - Uses a native UART (UART0); therefore not compatible with ATTINY
+; - Baud rate is fixed (set by a macro in the code). No auto bauding.
+; - Disables TX while not transmitting to allow for one wire flashing 
+;   (where RX and TX are shorted, for a multi drop bus)
+; - Also works with separate RX and TX; however an external pull up 
+;   on TX _may_ be required; alternatively you can modify the code
+;   in the ReceiveByte routine so that it won't disable TX.
+; - FIXES:
+;     - situations where booting onto a bus with active communication could
+;       lock the autobauding feature
+;     - times out and boots to application code if the host stops interacting
+;       with the bootloader
+;
+;-----------------------------------------------------------------------
+; Extended by Seed Robotics from 2017
+;-----------------------------------------------------------------------
+; Seed Robotics contributions are available from the Github
+; repository github.com/seedrobotics
+; The License and conditions remain as stated below, in the
+; original notice.
+;
+;
+;-----------------------------------------------------------------------
+; Written in 2011-2015 by Julien Thomas
+;
+; This program is free software; you can redistribute it and/or
+; modify it under the terms of the GNU General Public License
+; as published by the Free Software Foundation; either version 3
+; of the License, or (at your option) any later version.
+; This program is distributed in the hope that it will be useful,
+; but WITHOUT ANY WARRANTY; without even the implied warranty
+; of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+; See the GNU General Public License for more details.
+; You should have received a copy of the GNU General Public License
+; along with this program; if not, see:
+; http://www.gnu.org/licenses/
+;-----------------------------------------------------------------------
+;
+;
+;
+;***********************************************************************
+; OVERVIEW
+;***********************************************************************
+;
+; TSB assembly source is organized in 4 segments (approx. line numbers)
+;
+; ~   50 ... Global definitions
+; ~      ... TSB for ATmegas
+;
+;***********************************************************************
+; ADJUSTMENTS FOR INDIVIDUAL ASSEMBLY
+;***********************************************************************
+;
+; This Sourcecode is directly compatible to: AVRASM2, GAVRASM
+;
+.nolist
+;
+;-----------------------------------------------------------------------
+; SPECIFY TARGET AVR
+;-----------------------------------------------------------------------
+;
+; Comment in and provide def.inc file for target device
+;
+; [Examples]
+;
+;.include "tn2313def.inc"
+;.include "tn85def.inc"
+;.include "m8515def.inc"
+;.include "m168def.inc"
+;.include "m161def.inc"
+;.include "m324Adef.inc"
+;.include "m328Pdef.inc"
+;.include "tn441def.inc"
+;.include "tn167def.inc"
+;.include "tn861def.inc"
+;.include "tn841def.inc"
+;.include "tn84def.inc"
+;.include "m8def.inc"
+;.include "m644PAdef.inc"
+;.include "m644def.inc"
+;.include "tn167def.inc"
+;.include "tn25def.inc"
+;
+; [...]
+;
+;
+.list
+;
+;-----------------------------------------------------------------------
+; BUILD INFO
+;-----------------------------------------------------------------------
+; YY = Year - MM = Month - DD = Day
+.set    YY      =       21
+.set    MM      =       12
+.set    DD      =       21
+;
+.set BUILDSTATE = $F3   ; F1 fixed baud, pull up, derived from original (modified for fixed baud)
+						; F2 fixed baud, pull up, guaranteed minimum activation timeout in case of userpage data corruption
+						; F3 adds a CONSTANT with clock speed (Mhz) as word in the last page of memory (clock speed our defined CONSTANT)
+						
+;
+;-----------------------------------------------------------------------
+; TSB / TSB-INSTALLER SWITCH
+;-----------------------------------------------------------------------
+; 0 = Regular assembly to target address
+; Other value = NOT SUPPORTED
+;
+.set    TSBINSTALLER = 0
+;
+;-----------------------------------------------------------------------
+; F_CPU and Baud rate setting
+;-----------------------------------------------------------------------
+.equ	F_CPU	= 20000000
+.equ	BAUD	= 33333			; baudrate (notice some possible wrong cals: example for 56K, it is actually 55,555, so for BAUD_PRESC give an INT result of 8, we must set BAUD to 55500) 
+
+.equ	BAUD_PRESCx10	= (F_CPU * 10/16/BAUD) - 10	; baud prescale (regular formula = F_CPU * 10/16/BAUD - 1 but we do it x10 to check the rounding)
+
+; arredondar acima se necesssario
+.if BAUD_PRESCx10 - ( (BAUD_PRESCx10 / 10) * 10 ) >= 5  ; calculate the remainder: we rely on the fact these are integer divisions. Therefore, dividing by 10, rounds DOWN in integer division
+	.equ BAUD_PRESC = (F_CPU/16/BAUD) 
+	.warning "Incrementing default BAUD_PRESC formula by 1 due to rounding."
+
+.else
+	.equ BAUD_PRESC = (F_CPU/16/BAUD) - 1
+	.warning "Using default BAUD_PRESC formula (no rounding up)"
+.endif
+
+.if BAUD_PRESC > 255
+.error "ERROR: BAUD RATE TOO LOW. WE ONLY WRITE THE UBRRL REGISTER, SO UBRR MUST BE <255 FOR THIS CLOCK FREQ AND BAUD"
+.endif
+
+
+;***********************************************************************
+; AUTO-ADJUST FOR DIFFERENT ASSEMBLY OPTIONS
+;***********************************************************************
+;
+; Always set TINYMEGA=1 bc this code only supports ATMEGA
+
+.equ TINYMEGA=1
+
+.if FLASHEND > ($7fff)
+        .error "SORRY! DEVICES OVER 64 KB NOT SUPPORTED YET."
+        .exit
+.endif
+
+;-----------------------------------------------------------------------
+; Workarounds for devices with renamed or missing definitions
+;-----------------------------------------------------------------------
+;
+.ifndef SPMCSR                  ; SPMEN / PGERS / ...
+        .equ SPMCSR = SPMCR
+.endif
+
+.ifndef MCUSR                   ; PORF / EXTRF / BORF / WDRF
+        .equ MCUSR = MCUCSR
+.endif
+
+; Detect Attiny441/841 to amend missing pagesize and apply 4-page mode
+
+.set FOURPAGES = 0
+
+.if ((SIGNATURE_000 == $1E) && (SIGNATURE_002 == $15) && (SIGNATURE_001 == $92))
+                .equ PAGESIZE = 32
+                .set FOURPAGES = 1
+                .message "ATTINY441: 4-PAGE-ERASE MODE"
+.endif
+
+.if ((SIGNATURE_000 == $1E) && (SIGNATURE_002 == $15) && (SIGNATURE_001 == $93))
+                .equ PAGESIZE = 32
+                .set FOURPAGES = 1
+                .message "ATTINY841: 4-PAGE-ERASE MODE"
+.endif
+
+;-----------------------------------------------------------------------
+; Universal Constants and Registers
+;-----------------------------------------------------------------------
+
+.equ    REQUEST         = '?'           ; request / answer / go on
+.equ    CONFIRM         = '!'           ; confirm / attention
+
+; Current bootloader date coded into 16-bit number
+.equ    BUILDDATE   = YY * 512 + MM * 32 + DD
+
+; Other
+.equ    INFOLEN         = 8              ; *Words* of Device Info
+.equ    BUFFER          = SRAM_START
+
+; Registers (in use by TSB-Firmware and TSB-Installer for ATtinys)
+.def    avecl   = r4                    ; application vector temp low
+.def    avech   = r5                    ; application vector temp high
+.def    tmp1    = r16                   ; these are
+.def    tmp2    = r17                   ; universal
+.def    tmp3    = r18                   ; temporary
+.def    tmp4    = r19                   ; registers
+.def    bcnt    = r20                   ; page bytecounter
+.def    cntr1   = r21                   ; timeout counter
+.def    rxen    = r22					; check if RX enabled (meaning TX disabled)
+.def    utimeoutH = r23                  ; user timeout High byte     
+										; special purpose registers start at R26
+;
+;
+;***********************************************************************
+;***********************************************************************
+;***********************************************************************
+; START OF TSB FOR ATMEGAS
+;***********************************************************************
+;***********************************************************************
+;***********************************************************************
+;
+; TSB for ATmegas is always coded directly to target address.
+
+.if TINYMEGA == 1
+
+.message "ASSEMBLY OF TSB FOR ATMEGA"
+
+.equ    BOOTSTART       = (FLASHEND+1)-256      ; = 512 Bytes
+.equ    LASTPAGE        = BOOTSTART - PAGESIZE  ; = 1 page below TSB!
+
+.org    BOOTSTART
+
+RESET:
+        cli
+
+        in tmp4, MCUSR                  ; check reset condition
+        sbrc tmp4, WDRF                 ; in case of a Watchdog reset
+        rjmp APPJUMP                    ; immediately leave TSB
+
+        ldi tmp1, low (RAMEND)          ; write ramend low
+        out SPL, tmp1                   ; into SPL (stackpointer low)
+.ifdef SPH
+        ldi tmp1, high(RAMEND)          ; write ramend high for ATtinys
+        out SPH, tmp1                   ; with SRAM > 256 bytes
+		.message "PROVIDING FOR STACK BIGGER THAN 256 BYTES"
+.endif
+
+.ifndef DDRD2
+	.equ DDRD2 = DDD2
+.endif
+
+;-----------------------------------------------------------------------
+; ACTIVATION CHECK
+;-----------------------------------------------------------------------
+		; Configure UART; no autobauding in this version
+
+		ldi	tmp1,BAUD_PRESC			; load baud prescale
+		sts	UBRR0L,tmp1				; set baud prescale
+		; ldi	tmp2,HIGH(bpsc)			 ; save code by not loading UBBRH
+		;sts	UBRRH,tmp2				; to UBRR0
+		;ldi	tmp2,( (1<<RXEN0) )   	; enable transmiter and receiver
+		;sts	UCSR0B,tmp2	
+
+		; Enable Pull up on Port D2 (PD2)
+		cbi DDRD, DDRD2
+		sbi PORTD, PORTD2
+
+		; we will enable RNEN/TXEN in the ReceiveByte and TransmitByte routines
+
+        rcall ZtoLASTPAGE               ; set Z to start'o'LASTPAGE
+        adiw zl, 2                      ; skip first 2 bytes (APPJUMP)
+        lpm utimeoutH, z+               ; load TIMEOUT byte and store for use in RX byte timeout
+		ori utimeoutH, (F_CPU / 1000000); prevent bootloader lockout due if it gets an invalid (to small) timeout setting
+										; this ensures value is at least the clock rate, which shoudl give about 40ms
+		clr tmp2						; apparently at times this is not set to 0 on boot? (seen while in debugWire)
+		clr rxen						; same as above
+
+WRX1To:
+		; we'll check the X register which is where ReceibeByte controls the timeout
+		; the overall timeout of receive byte is the timeout set by the user
+		; therefore, if we get characters while X> 0 we're attempting to activate bootloader;
+		; if not, if X=0 we timedout and go to app start
+		rcall ReceiveByte
+		brcs WRX2To						; if X got to 0 (i.e. carry set), assume we timed out
+		cpi tmp1, '@'                   ; did we get an activation char = "@"
+		breq ActCharRcvd
+WRX2To:
+		rjmp APPJUMP                    ; not an activation char goto APPJUMP in LASTPAGE
+        
+
+ActCharRcvd:
+		inc tmp2
+		cpi tmp2, 3
+		brne WRX1To						; branch if not yet at 3; 
+										; otherwise fall through to password check
+
+;-----------------------------------------------------------------------
+; CHECK PASSWORD / EMERGENCY ERASE
+;-----------------------------------------------------------------------
+		; we use the user timeout (utimeoutH) register for COMM timeout 
+		; when we don't get valid data
+		; increase this value to a fixed one now, to cope
+		; with cases where the user timeout is set so low that we don't have time to
+		; do anything
+		ldi utimeoutH, (F_CPU / 78500) ; this should result in 255 for 20Mhz and proportionally
+									   ; less for lower Clocks, so that we get the same time approx. 2.4sec
+
+CheckPassword:
+
+chpw0:  ser tmp4                        ; tmp4 = 255 enables comparison
+chpw1:  lpm tmp3, z+                    ; load pw character from Z
+        and tmp3, tmp4                  ; if tmp4 = 0 disables comparison, for wrong password scenarios
+        cpi tmp3, 255                   ; byte value 255 indicates
+        breq chpwx                      ; end of password -> success
+chpw2:  rcall Receivebyte               ; else receive next character
+        cpi tmp1, 0                     ; rxbyte = 0 will branch
+        breq chpwee                     ; to confirm emergency erase
+        cp  tmp1, tmp3                  ; compare password with rxbyte
+        breq chpw0                      ; if equal check next character
+        clr  tmp4                       ; tmp4 = 0 to loop forever
+        rjmp chpw1                      ; and smoothen power profile
+chpwee:
+        ; Fix for ISSUE #1: only check for Emergency Erase if we haven't
+		; gotten a wrong password; if we got a wrong password
+		; then we should stay in loop and not escape to Emergency
+		; Erase
+		cpi tmp4, 0						; if tmp4=0 we are set to loop forever
+		breq chpw1
+        rcall RequestConfirm            ; request confirm
+        brts chpa                       ; not confirmed, leave
+        rcall RequestConfirm            ; request 2nd confirm
+        brts chpa                       ; can't be mistake now
+        rcall EmergencyErase            ; go, emergency erase!
+        rjmp  Mainloop
+chpa:
+        rjmp APPJUMP                    ; start application
+chpwx:
+;       rjmp SendDeviceInfo             ; go on to SendDeviceInfo
+
+;-----------------------------------------------------------------------
+; SEND DEVICEINFO
+;-----------------------------------------------------------------------
+
+SendDeviceInfo:
+        ldi zl, low (DEVICEINFO*2)      ; load address of deviceinfo
+        ldi zh, high(DEVICEINFO*2)      ; low and highbyte
+        ldi bcnt, INFOLEN*2
+        rcall SendFromFlash
+
+;-----------------------------------------------------------------------
+; MAIN LOOP TO RECEIVE AND EXECUTE COMMANDS
+;-----------------------------------------------------------------------
+
+Mainloop:
+        clr zl                          ; clear Z pointer
+        clr zh                          ; which is frequently used
+        rcall SendConfirm               ; send CONFIRM via RS232
+        rcall Receivebyte               ; receive command via RS232
+        rcall CheckCommands             ; check command letter
+        rjmp Mainloop                   ; and loop on
+
+;-----------------------------------------------------------------------
+; CHANGE USER DATA IN LASTPAGE
+;-----------------------------------------------------------------------
+
+ChangeSettings:
+        rcall GetNewPage                ; get new LASTPAGE contents
+        brtc ChangeS0                   ; from Host (if confirmed)
+        ret
+ChangeS0:
+        rcall ZtoLASTPAGE               ; re-write LASTPAGE
+        rcall EraseFlashPage
+        rcall WritePage                 ; erase and write LASTPAGE
+
+;-----------------------------------------------------------------------
+; SEND USER DATA FROM LASTPAGE
+;-----------------------------------------------------------------------
+
+ControlSettings:
+        rcall ZtoLASTPAGE               ; point to LASTPAGE
+;       rcall SendPageFromFlash
+
+;-----------------------------------------------------------------------
+; SEND DATA FROM FLASH MEMORY
+;-----------------------------------------------------------------------
+
+SendPageFromFlash:
+        ldi bcnt, low (PAGESIZE*2)      ; whole Page to send
+SendFromFlash:
+        rcall SPMwait                   ; (re)enable RWW read access
+        lpm tmp1, z+                    ; read directly from flash
+        rcall Transmitbyte              ; and send out to RS232
+        dec bcnt                        ; bcnt is number of bytes
+        brne SendFromFlash
+        ret
+
+;-----------------------------------------------------------------------
+; READ APPLICATION FLASH
+;-----------------------------------------------------------------------
+; read and transmit application flash area (pagewise)
+
+ReadAppFlash:
+RAF0:
+        rcall RwaitConfirm
+        brts RAFx
+        rcall SendPageFromFlash
+RAF1:
+        cpi zl, low (LASTPAGE*2)        ; count up to last byte
+        brne RAF0                       ; below LASTPAGE
+        cpi zh, high(LASTPAGE*2)
+        brne RAF0
+RAFx:
+        ret
+
+;-----------------------------------------------------------------------
+; WRITE APPLICATION FLASH
+;-----------------------------------------------------------------------
+; Write Appflash pagewise, don't modify anything for ATmegas
+
+WriteAppFlash:
+        rcall EraseAppFlash             ; Erase whole app flash
+Flash2:
+        rcall GetNewPage                ; get next page from host
+        brts FlashX                     ; stop on user's behalf
+Flash3:
+        rcall WritePage                 ; write page data into flash
+Flash4:
+        cpi zh, high(LASTPAGE*2-1)      ; end of available Appflash?
+        brne Flash2                     ; if Z reached last location
+        cpi zl, low (LASTPAGE*2-1)      ; then we are finished
+        brne Flash2                     ; else go on
+FlashX:
+        ret                             ; we're already finished!
+
+;-----------------------------------------------------------------------
+; WRITE FLASH PAGE FROM BUFFER, VERIFYING AND VERIFY-ERROR-HANDLING
+;-----------------------------------------------------------------------
+
+WritePage:
+        rcall YtoBUFFER                 ; Y=BUFFER, bcnt=PAGESIZE*2
+WrPa1:
+        ld r0, y+                       ; fill R0/R1 with word
+        ld r1, y+                       ; from buffer position Y / Y+1
+        ldi tmp1, 0b00000001            ; set only SPMEN in SPMCSR
+        out SPMCSR, tmp1                ; to activate page buffering
+        spm                             ; store word in page buffer
+        adiw zl, 2                      ; and forward to next word
+        subi bcnt, 2
+        brne WrPa1
+        ; Z = start of next page now
+        subi zl, low (PAGESIZE*2)       ; point back Z to
+        sbci zh, high(PAGESIZE*2)       ; start of current page
+        ; Z = back on current page's start
+WrPa2:
+        ldi tmp1, 0b00000101            ; enable PRWRT + SPMEN
+        out SPMCSR, tmp1                ; in SPMCSR
+        spm                             ; write whole page to flash
+WrPa3:
+        in tmp1, SPMCSR                 ; wait for flash write finished
+        sbrc tmp1, 0                    ; skip if SPMEN (bit0) cleared
+        rjmp WrPa3                      ; ITS BEEN WRITTEN
+        subi zl, low (-PAGESIZE*2)      ; same effect as
+        sbci zh, high(-PAGESIZE*2)      ; Z = Z + PAGESIZE*2
+        ret
+
+;-----------------------------------------------------------------------
+; CHECK COMMANDS
+;-----------------------------------------------------------------------
+
+CheckCommands:
+        cpi tmp1, 'c'                   ; read LASTPAGE
+        breq ControlSettings
+        cpi tmp1, 'C'                   ; write LASTPAGE
+        breq ChangeSettings
+        cpi tmp1, 'f'                   ; read Appflash
+        breq ReadAppFlash
+        cpi tmp1, 'F'                   ; write Appflash
+        breq WriteAppFlash
+        cpi tmp1, 'e'                   ; read EEPROM
+        breq EepromRead
+        cpi tmp1, 'E'                   ; write EEPROM
+        breq EEpromWrite
+        rjmp APPJUMP                    ; else start application
+
+;-----------------------------------------------------------------------
+; EEPROM READ/WRITE ACCESS
+;-----------------------------------------------------------------------
+
+EepromWrite:
+EEWr0:
+        rcall GetNewPage                ; get EEPROM datablock
+        brts EERWFx                     ; or abort on host's demand
+EEWr1:
+        rcall YtoBUFFER                 ; Y = Buffer and Bcnt = blocksize
+EEWr2:
+        ld tmp1, y+                     ; read EEPROM byte from buffer
+        rcall EEWriteByte
+        dec bcnt                        ; count down block byte counter
+        brne EEWr2                      ; loop on if block not finished
+        rjmp EeWr0
+
+;-----------------------------------------------------------------------
+
+EEpromRead:
+EeRe1:
+        rcall RwaitConfirm              ; wait to confirm
+        brts EERWFx                     ; else we are finished
+        ldi bcnt, low(PAGESIZE*2)       ; again PAGESIZE*2 is blocksize
+EERe2:
+        out EEARL, zl                   ; current EEPROM address low
+        .ifdef  EEARH
+        out EEARH, zh                   ; current EEPROM address high
+        .endif
+        sbi EECR, 0                     ; set EERE - EEPROM read enable
+        in tmp1, EEDR                   ; read byte from current address
+        rcall Transmitbyte              ; send out to RS232
+        adiw zl,1                       ; count up EEPROM address
+        dec bcnt                        ; count down block byte counter
+        brne EERe2                      ; loop on if block not finished
+        rjmp EERe1
+EERWFx:
+        ret
+
+;-----------------------------------------------------------------------
+
+EEWriteByte:
+        out EEDR, tmp1                  ; write to EEPROM data register
+        out EEARL, zl                   ; current EEPROM address low
+        .ifdef  EEARH
+        out EEARH, zh                   ; high EEARH for some attinys
+        .endif
+        sbi EECR, 2                     ; EEPROM master prog enable
+        sbi EECR, 1                     ; EEPE initiate prog cycle
+EeWB:
+        sbic EECR, 1                    ; wait write cycle to complete
+        rjmp EeWB                       ; before we can go on
+        adiw zl,1                       ; count up EEPROM address
+        ret
+
+;-----------------------------------------------------------------------
+; GET NEW PAGE
+;-----------------------------------------------------------------------
+
+GetNewPage:
+        rcall RequestConfirm            ; check for Confirm
+        brts GNPx                       ; abort if not confirmed
+GNP0:
+        rcall YtoBUFFER                 ; Y = BUFFER, bcnt = PAGESIZE*2
+GNP1:
+        rcall ReceiveByte               ; receive serial byte
+        st y+, tmp1                     ; and store in buffer
+        dec bcnt                        ; until full page loaded
+        brne GNP1                       ; loop on
+GNPx:
+        ret                             ; finished
+;-----------------------------------------------------------------------
+; REQUEST TO CONFIRM / AWAIT CONFIRM COMMAND
+;-----------------------------------------------------------------------
+
+RequestConfirm:
+        ldi tmp1, REQUEST               ; send request character
+        rcall Transmitbyte              ; prompt to confirm (or not)
+
+RwaitConfirm:
+        rcall ReceiveByte               ; get host's reply
+        clt                             ; set T=0 for confirmation
+        cpi tmp1, CONFIRM               ; if host HAS sent CONFIRM
+        breq RCx                        ; return with the T=0
+        set                             ; else set T=1 (NOT CONFIRMED)
+RCx:
+        ret                             ; whether confirmed or not
+
+;-----------------------------------------------------------------------
+; FLASH ERASE TOP-TO-BOTTOM ( (BOOTSTART-1) ... $0000)
+;-----------------------------------------------------------------------
+
+EraseAppFlash:
+        rcall ZtoLASTPAGE               ; point Z to LASTPAGE, directly
+EAF0:
+        subi zl, low (PAGESIZE*2)
+        sbci zh, high(PAGESIZE*2)
+        rcall EraseFlashPage
+        brne EAF0                       ; until first page reached
+EAFx:   ret                             ; and leave with Z = $0000
+
+;-----------------------------------------------------------------------
+; EMERGENCY ERASE OF FLASH / EEPROM / USERDATA
+;-----------------------------------------------------------------------
+
+EmergencyErase:
+        rcall EraseAppFlash             ; erase Application Flash
+        ser tmp1                        ; byte value for EEPROM writes
+EEE0:
+        rcall EEWriteByte               ; write EEPROM byte, Z = Z + 1
+        cpi zh, high(EEPROMEND+1)+2     ; EEPROMEND
+        brne EEE0                       ; and loop on until finished
+
+        rcall ZtoLASTPAGE               ; LASTPAGE is to be erased
+;        rcall EraseFlashPage
+
+;-----------------------------------------------------------------------
+; ERASE ONE FLASH PAGE
+;-----------------------------------------------------------------------
+
+EraseFlashPage:
+        ldi tmp1, 0b00000011            ; enable PGERS + SPMEN
+        out SPMCSR, tmp1                ; in SPMCSR and erase current
+        spm                             ; page by SPM (MCU halted)
+
+; Waiting for SPM to be finished is *obligatory* on ATmegas!
+SPMwait:
+        in tmp1, SPMCSR
+        sbrc tmp1, 0                    ; wait previous SPMEN
+        rjmp SPMwait
+        ldi tmp1, 0b00010001            ; set RWWSRE and SPMEN
+        out SPMCSR, tmp1
+        spm
+        ret
+
+;-----------------------------------------------------------------------
+; OTHER SUBROUTINES
+;-----------------------------------------------------------------------
+
+YtoBUFFER:
+        ldi yl, low (BUFFER)            ; reset pointer
+        ldi yh, high(BUFFER)            ; to programming buffer
+        ldi bcnt, low(PAGESIZE*2)       ; and often needed
+        ret
+
+;-----------------------------------------------------------------------
+
+ZtoLASTPAGE:
+        ldi zl, low (LASTPAGE*2)        ; reset Z to LASTPAGE start
+        ldi zh, high(LASTPAGE*2)
+        ret
+
+;-----------------------------------------------------------------------
+; RS232 RECEIVE BYTE
+;-----------------------------------------------------------------------
+
+; uses: tmp1 (received data byte), cntr1 (for timeout)
+; also uses utimeoutH which holds the default timeout defined by the user
+; and X which is actually used to count down
+SetRX:
+		ldi	tmp1,(1<<RXEN0) 		; enable receiver (Transmitter disabled)
+		sts	UCSR0B,tmp1
+		ser rxen
+
+ReceiveByte:
+		sbrs rxen, 0
+		rjmp SetRX		
+
+		; outer counter
+		mov xh, utimeoutH
+		;ldi xl, 128
+
+ReceiveByteShortTimeout:
+		ser cntr1						; inner counter reset
+
+ReceiveByteShortTimeout1:		
+		lds tmp1, UCSR0A				; load UART status register A
+		sbrc tmp1, RXC0					; if not RXComplete, skip
+		rjmp LoadRXByte
+		dec cntr1						; if counter not zero
+		brne ReceiveByteShortTimeout1	; cycle again; else fall through
+		sbiw xl, 1						; dec outter counter
+		brcc ReceiveByteShortTimeout	; continue of outter counetr still active
+		;ret							; 
+
+LoadRXByte:
+		lds tmp1, UDR0					; load received character even if RXC is not set
+		ret								; (it loads 0 and UDR FIFO should recover for next char)
+
+;-----------------------------------------------------------------------
+; RS232 SEND CONFIRM CHARACTER
+;-----------------------------------------------------------------------
+
+SendConfirm:
+        ldi tmp1, CONFIRM
+        rjmp Transmitbyte
+
+;-----------------------------------------------------------------------
+; RS232 TRANSMIT BYTE
+;-----------------------------------------------------------------------
+; uses: tmp1 (transmit byte will be shifted out), tmp2 (bitcounter)
+;
+
+SetTX:
+		ldi	tmp2,(1<<TXEN0)   	; enable transmitter (Receiver disabled)
+		sts	UCSR0B,tmp2	
+		clr rxen
+
+		; wait some guard time to allow receiving devices ot transition
+		; from TX t RX state
+		ser cntr1						; inner counter reset
+SetTXShortTimeout:
+		nop
+		dec cntr1						; if counter not zero
+		brne SetTXShortTimeout			; cycle again; else fall through
+
+
+TransmitByte:
+		sbrc rxen, 0
+		rjmp SetTX
+
+		; no need to wait for UDRE bc we will wait for TXC on
+		; every char transmitted. TXC occurs later that UDRE
+		; so UDRE should be asserted when TXC asserts
+		sts UDR0, tmp1
+
+WaitForTXC:
+		lds tmp2, UCSR0A		; wait for TXC (and not UDRE)
+		sbrs tmp2, TXC0			; bc after this char we may transition
+		rjmp WaitForTXC			; to receiving chars and we want to make sure we get a clean transition
+		; we need to write a 1 to clear the TXC flag; otherwise the flag won't clear
+		sts UCSR0A, tmp2		; tmp2 should contain an asserted TXC bit
+		ret
+
+
+;-----------------------------------------------------------------------
+; ATMEGA APPJUMP = SIMPLE JUMP TO $0000 (ORIGINAL RESET VECTOR)
+;-----------------------------------------------------------------------
+; Boot Reset Vector (BOOTRST) must be activated for TSB on ATmegas.
+; After timeout or executing commands, TSB for ATmegas will simply
+; handover to the App by a (relative or absolute) jump to $0000.
+
+APPJUMP:
+        rcall SPMwait                   ; make sure everything's done
+
+.if FLASHEND >= ($1fff)
+        jmp  $0000                      ; absolute jump
+.else
+        rjmp $0000                      ; relative jump
+.endif
+
+
+DEVICEINFO:
+.message "DEVICE INFO BLOCK FOR ATMEGA"
+.db "TSB", low (BUILDDATE), high (BUILDDATE), BUILDSTATE
+.db SIGNATURE_000, SIGNATURE_001, SIGNATURE_002, low (PAGESIZE)
+.dw BOOTSTART-PAGESIZE
+.dw EEPROMEND
+.db $AA, $AA
+
+
+;-----------------------------------------------------------------------
+; DEVICE INFO BLOCK = PERMANENT DATA
+;-----------------------------------------------------------------------
+
+; set last word with the clock speed
+.org FLASHEND
+.dw (F_CPU/1000000)
+
+//.message "SAVING CLOCK SPEED IN LAST BYTE AS " (F_CPU/1000000) " Mhz"
+
+.message "ASSEMBLY OF TSB FOR ATMEGA SUCCESSFULLY FINISHED!"
+
+.endif               ; closing TSB for ATmega sourcecode;
+
+;***********************************************************************
+; END OF TSB FOR ATMEGAS
+;***********************************************************************
+
+.exit
+
+;***********************************************************************
+;***********************************************************************
+;***********************************************************************
+; END OF CONDITIONAL ASSEMBLY SOURCE OF TSB FOR ATTINYS AND ATMEGAS
+;***********************************************************************
+;***********************************************************************
+;***********************************************************************
+
+

pureboot/README.md

@@ -0,0 +1,123 @@
+# pureboot
+
+A serial bootloader on [libavr](https://git.blackmark.me/avr/libavr), pure by
+constraint: one C++ source, no inline assembly, no global register variables
+(attributes allowed), built for every chip libavr targets, **512 bytes on
+each** — 490 B on the ATtiny13A, 510 B on the ATtiny85, 484 B on the
+ATmega328P. The device speaks primitives; every composite — verify, erase,
+reset-vector surgery, timeout configuration — lives in the host tool
+(`pureboot.py`).
+
+## Link
+
+| Chip | Serial | Baud | Clock assumed |
+|---|---|---|---|
+| ATmega328P | USART0, RXD/TXD = PD0/PD1 | 115200 8N1 | 16 MHz crystal |
+| ATtiny85 | software UART, RX = PB0, TX = PB1 | 57600 8N1 | 8 MHz internal RC |
+| ATtiny13A | software UART, RX = PB0, TX = PB1 | 57600 8N1 | 9.6 MHz internal RC |
+
+The tiny RX pin has its pull-up enabled; TX idles high. All multi-byte
+quantities on the wire are little-endian.
+
+## Activation
+
+Reset enters the loader (BOOTRST on the mega, the patched reset vector on the
+tinies) — except a watchdog reset, which hands straight to the application
+(the application owns its watchdog; it must clear WDRF itself, which also
+releases the WDRF-forced WDE).
+
+The host then has one activation window per awaited byte to knock: `p` then
+`b`. Each awaited byte gets a fresh window; any other byte is discarded and
+awaited again (line noise cannot lock the loader, only delay it). A window
+expiring with an idle line boots the application.
+
+The window length in seconds is the **last EEPROM cell** (address
+`eeprom_size - 1`); `0x00` and the erased `0xff` both mean the 4 s default,
+so a full EEPROM erase resets the timeout rather than maxing it. The host
+changes it with the ordinary EEPROM-write command.
+
+## Session
+
+After the knock the loader stays in its command loop until `G` or a reset.
+Before reading each command it waits for any pending EEPROM write to finish
+and sends the prompt `+` (0x2b) — the prompt is therefore also the completion
+ack of the previous command. A session is: await `+`, send a command, read
+its reply, repeat.
+
+| Cmd | Arguments | Reply |
+|---|---|---|
+| `b` | — | the 12-byte info block |
+| `R` | addr16, n8 | n flash bytes (n = 0 means 256) |
+| `W` | addr16, then one page of data | — (completion = next prompt) |
+| `r` | addr16, n8 | n EEPROM bytes (n = 0 means 256) |
+| `w` | addr16, n8, then n data bytes | `+` per byte, sent once its write has begun |
+| `F` | — | 4 bytes: low fuse, lock, extended fuse, high fuse |
+| `G` | — | `+`, then the application runs |
+| other | — | ignored; the loop re-prompts (send a junk byte, await `+`, to resync) |
+
+`W` streams exactly one SPM page (size from the info block) into the buffer,
+then erases and programs; the address must be page-aligned. Pages inside the
+loader's own 512 bytes are drained but never programmed — a broken host
+cannot brick the chip. `w` is host-paced: send the next byte only after the
+previous byte's `+`. `F` returns the bytes in the hardware's Z order; on a chip without an
+extended fuse byte (the ATtiny13A) that slot carries no meaning. Fuse *writing* does not
+exist: SPM reaches flash (and, on the mega, lock bits) only — fuse bytes are
+external-programming territory by hardware.
+
+The info block (`b`):
+
+| Offset | Content |
+|---|---|
+| 0–2 | `'P'`, `'B'`, protocol version (1) |
+| 3–5 | device signature |
+| 6 | SPM page size in bytes |
+| 7–8 | loader base — application flash ends here |
+| 9–10 | EEPROM size |
+| 11 | bit 0 set: host must patch the reset vector (no hardware boot section) |
+
+Composites are the host's job: verify = read back and compare, erase =
+write `0xff` (per page for flash, per byte for EEPROM), timeout = EEPROM
+write to the last cell.
+
+## Deployment
+
+**ATmega328P**: program the loader at 0x7e00 with an external programmer;
+fuses BOOTSZ = 11 (256 words) and BOOTRST programmed. Applications are
+flashed unmodified — reset re-vectors to the loader in hardware, word 0
+stays the application's own reset vector, and `G` jumps to 0.
+
+**Tinies** (no boot section): program the loader at `flash - 512`; erased
+flash below it walks up into the loader, so a virgin chip activates. When
+flashing an application the host performs reset-vector surgery: the
+application's own `rjmp` target is re-encoded as a trampoline `rjmp` in the
+word just below the loader (`base - 2`, where `G` jumps), and word 0 is
+rewritten to `rjmp` to the loader base. Every other vector stays the
+application's. Page 0 is written last, so an interrupted flash leaves word 0
+erased and the chip still falls through to the loader on the next reset.
+
+## Host tool
+
+`pureboot.py` — Python 3, standard library only (termios drives any tty,
+a USB adapter as well as a simavr pty):
+
+    pureboot.py --port /dev/ttyUSB0 --baud 57600 \
+        --info --fuses --flash app.hex --timeout 10
+
+Operations run in a fixed order within one session: info, fuses, flash
+(erase / program / read / verify), EEPROM (erase / program / read / verify),
+timeout — then the loader hands over to the application; `--stay` keeps the
+session alive instead, and a later invocation reconnects into it (the knock
+converges there too). `--flash` and `--eeprom` verify by read-back unless
+`--no-verify`; images are raw binary, or Intel HEX by extension.
+
+## Tests
+
+Per chip preset, `ctest` runs the 512-byte size gate and the end-to-end
+protocol test: a simavr device (`test/pureboot_device.c` — the mega's USART
+as a pty; on the tinies a cycle-timed GPIO⇄pty bridge for the software UART,
+plus the SPM/NVM module simavr's tiny cores lack) driven by the real host
+tool through knock-from-reset, program + verify of both memories, timeout
+configuration, session reconnect, an external reset through the patched
+vector, and the hand-over to a fixture application whose banner proves the
+launch — cross-checked against the simulator's ground-truth memory dumps and
+an independent decode of the surgery's rjmp words.

pureboot/pureboot.cpp

@@ -0,0 +1,326 @@
+// pureboot — a serial bootloader on libavr, pure by constraint: one C++
+// source with no inline assembly and no global register variables, built for
+// every chip libavr targets, 512 bytes on each. The device speaks primitives
+// — read/program flash, read/write EEPROM, fuse bytes, an info block, run —
+// and everything composite (verify, erase, reset-vector surgery on the
+// tinies, timeout configuration) lives in the host tool. Protocol reference:
+// README.md next to this file.
+//
+// Entry: reset lands in avr::startup::entry below (BOOTRST on the mega; the
+// patched reset vector — or erased flash walking up into the loader — on the
+// tinies). A watchdog reset hands straight to the application. Otherwise the
+// host has one activation window — EEPROM's last cell, in seconds — to knock
+// ("pb"); an idle line boots the application. A session then stays in the
+// command loop until 'G' hands over or the chip resets.
+
+#include <libavr/libavr.hpp>
+
+using namespace avr::literals;
+namespace spm = avr::spm;
+namespace ee = avr::eeprom;
+
+namespace pureboot {
+namespace {
+
+// Purely polled — interrupts stay off, every guard folds to nothing.
+constexpr auto off = avr::irq::guard_policy::unused;
+
+constexpr std::uint8_t ack = '+';
+
+// Per-chip personality, from the chip database: the clocks the dogfood
+// boards run (16 MHz crystal on the mega, calibrated RC on the tinies) and
+// the device signature (compile-time data — the tiny13A cannot even read its
+// signature row from code).
+consteval avr::hertz_t clock()
+{
+	if (avr::hw::db.name == "ATtiny13A")
+		return 9.6_MHz;
+	if (avr::hw::db.name == "ATtiny85")
+		return 8_MHz;
+	return 16_MHz;
+}
+
+consteval std::array<std::uint8_t, 3> signature()
+{
+	if (avr::hw::db.name == "ATtiny13A")
+		return {0x1e, 0x90, 0x07};
+	if (avr::hw::db.name == "ATtiny85")
+		return {0x1e, 0x93, 0x0b};
+	return {0x1e, 0x95, 0x0f};
+}
+
+using dev = avr::device<{.clock = clock()}>;
+
+// Geometry: the loader owns the top 512 bytes of flash; the byte below it is
+// the trampoline word (the application's relocated reset vector) on chips
+// without a hardware boot section. The RWWSRE bit marks a separate boot
+// section — on classic AVR the two capabilities coincide.
+constexpr std::uint16_t boot_bytes = 512;
+constexpr std::uint16_t base = static_cast<std::uint16_t>(spm::flash_bytes - boot_bytes);
+constexpr std::uint16_t page = spm::page_bytes;
+constexpr bool boot_section = avr::hw::db.field_index("SPMCSR", "RWWSRE") >= 0;
+
+// The activation timeout lives in EEPROM's last cell, in seconds; the host
+// rewrites it with the ordinary EEPROM-write command. An unprogrammed cell —
+// 0x00 or the erased 0xff — means the 4 s default: a stray value can never
+// floor the window to nothing and lock the loader out, and erasing the whole
+// EEPROM resets the timeout instead of maxing it to 255 s.
+constexpr std::uint16_t timeout_cell = avr::hw::db.mem.eeprom_size - 1;
+constexpr std::uint8_t default_seconds = 4;
+
+// The 12-byte info block the host reads with the 'b' command; flash-resident
+// (there is no crt to copy a .data image).
+inline constexpr std::array<std::uint8_t, 12> info_data = {
+    'P',
+    'B',
+    1, // magic, protocol version
+    signature()[0],
+    signature()[1],
+    signature()[2],
+    static_cast<std::uint8_t>(page),
+    base & 0xff,
+    base >> 8, // app flash ends here; loader base
+    avr::hw::db.mem.eeprom_size & 0xff,
+    avr::hw::db.mem.eeprom_size >> 8,
+    boot_section ? 0 : 1, // bit 0: host must patch the reset vector (no hardware boot section)
+};
+using info = avr::flash_table<info_data>;
+
+// The serial link: the hardware USART where the chip has one, the polled
+// software UART (no vector — the table belongs to the application) on PB0/PB1
+// elsewhere. Both are class templates on the clock so only the selected
+// backend is ever instantiated. pending() is the cheap line test the
+// activation window polls; rx() then picks the byte up.
+template <avr::hertz_t C>
+consteval std::int16_t rxc_field()
+{
+	return avr::hw::db.field_index("UCSR0A", "RXC0");
+}
+
+template <avr::hertz_t C>
+struct hardware_link {
+	using uart = avr::uart::usart0<C, {.baud = 115200_Bd, .max_baud_error = 2.5_pct}>;
+
+	static void init()
+	{
+		avr::init<uart>();
+	}
+
+	static bool pending()
+	{
+		return avr::hw::field_impl<rxc_field<C>()>::test();
+	}
+
+	static std::uint8_t rx()
+	{
+		return uart::read_blocking();
+	}
+
+	static void tx(std::uint8_t byte)
+	{
+		uart::write(byte);
+	}
+};
+
+template <avr::hertz_t C>
+struct software_link {
+	using rx_t = avr::uart::software_rx_polled<C, avr::pb0, 57600_Bd>;
+	using tx_t = avr::uart::software_tx<C, avr::pb1, 57600_Bd>;
+
+	static void init()
+	{
+		avr::init<rx_t, tx_t>();
+	}
+
+	static bool pending()
+	{
+		return !avr::io::input<avr::pb0>::read(); // a start bit has begun
+	}
+
+	static std::uint8_t rx()
+	{
+		return rx_t::template read_blocking<off>();
+	}
+
+	static void tx(std::uint8_t byte)
+	{
+		tx_t::template write<off>(byte);
+	}
+};
+
+using link = std::conditional_t<avr::hw::db.has_reg("UDR0"), hardware_link<dev::clock>, software_link<dev::clock>>;
+
+// The application's entry: the linker pins pureboot_app to 0x0000 on the
+// mega (reset re-vectors here through BOOTRST, so address 0 stays the
+// application's own vector) and to the trampoline word at base - 2 on the
+// tinies (--defsym in CMakeLists.txt).
+extern "C" [[noreturn]] void pureboot_app();
+
+[[noreturn]] void run_app()
+{
+	pureboot_app();
+}
+
+// One activation tick is 65536 pending() polls — a pin (or flag) test plus a
+// 16-bit countdown, about 8 cycles. Whole-second precision is all the
+// timeout cell promises; the seconds count stays a loop bound (a runtime
+// multiply would drag libgcc's __mulhi3 into the MUL-less tinies).
+consteval std::uint16_t ticks_per_second()
+{
+	return static_cast<std::uint16_t>(dev::clock.hz / (65536ull * 8u));
+}
+static_assert(ticks_per_second() >= 1);
+
+bool pending_before(std::uint8_t seconds)
+{
+	do {
+		std::uint16_t ticks = ticks_per_second();
+		do {
+			std::uint16_t spins = 0; // wraps first, so 65536 polls per tick
+			do {
+				if (link::pending())
+					return true;
+			} while (--spins);
+		} while (--ticks);
+	} while (--seconds);
+	return false;
+}
+
+// A knock byte under the activation deadline: an idle line means no host is
+// there, and the application runs.
+std::uint8_t rx_deadline(std::uint8_t seconds)
+{
+	if (!pending_before(seconds))
+		run_app();
+	return link::rx();
+}
+
+std::uint16_t rx16()
+{
+	std::uint8_t low = link::rx();
+	return static_cast<std::uint16_t>(low | (link::rx() << 8));
+}
+
+const std::uint8_t *flash_ptr(std::uint16_t address)
+{
+	return reinterpret_cast<const std::uint8_t *>(address);
+}
+
+// The streamers take the count in the wire's 8-bit form: 0 means 256.
+void send_flash(std::uint16_t address, std::uint8_t count)
+{
+	do
+		link::tx(avr::flash_load(flash_ptr(address++)));
+	while (--count);
+}
+
+void send_eeprom(std::uint16_t address, std::uint8_t count)
+{
+	do
+		link::tx(ee::read(address++));
+	while (--count);
+}
+
+// EEPROM write, host-paced: each ack goes out once the byte's write has
+// begun, so the next byte arrives while it completes and the following
+// write's own ready-wait sees an idle line. Nothing is ever missed, on
+// either serial backend, without a buffer.
+void store_eeprom(std::uint16_t address, std::uint8_t count)
+{
+	do {
+		ee::write<off>(address++, link::rx());
+		link::tx(ack);
+	} while (--count);
+}
+
+// One flash page: stream the bytes into the SPM buffer as little-endian
+// words, then erase and program. Addresses in the loader's own 512 bytes
+// are drained but never programmed — a broken host cannot brick the chip.
+// On the mega the RWW section is re-enabled so reads work immediately.
+void program_flash(std::uint16_t address)
+{
+	for (std::uint16_t i = 0; i < page; i += 2) {
+		std::uint8_t low = link::rx();
+		std::uint8_t high = link::rx();
+		spm::fill<off>(address + i, static_cast<std::uint16_t>(low | (high << 8)));
+	}
+	if (address < base) {
+		spm::erase_page<off>(address);
+		spm::wait();
+		spm::write_page<off>(address);
+		spm::wait();
+		if constexpr (boot_section)
+			spm::rww_enable<off>();
+	}
+}
+
+// The four fuse/lock bytes in the hardware's own Z order: low, lock,
+// extended, high. Writing fuses is not a thing self-programming can do on
+// AVR — SPM reaches flash (and boot lock bits) only.
+void send_fuses()
+{
+	for (std::uint8_t which = 0; which < 4; ++which)
+		link::tx(spm::read_fuse<off>(static_cast<spm::fuse>(which)));
+}
+
+[[noreturn]] void run()
+{
+	// A watchdog reset belongs to the application (whose watchdog stays
+	// forced on until it clears WDRF) — no activation window in its way.
+	if (avr::hw::mcusr::wdrf.test())
+		run_app();
+
+	link::init();
+
+	std::uint8_t seconds = ee::read(timeout_cell);
+	if (seconds == 0 || seconds == 0xff)
+		seconds = default_seconds;
+
+	// The knock: 'p' then 'b', each under a fresh window; any other byte is
+	// line noise and waits again. Falling out of a window runs the app.
+	while (rx_deadline(seconds) != 'p' || rx_deadline(seconds) != 'b') {
+	}
+
+	for (;;) {
+		// No prompt while an EEPROM write runs: a pending write blocks SPM
+		// and fuse reads (§26.2.1), and the ack tells the host all is done.
+		ee::wait();
+		link::tx(ack);
+		switch (link::rx()) {
+		case 'b': // info block
+			send_flash(reinterpret_cast<std::uint16_t>(info::storage.data()), info::size());
+			break;
+		case 'R': { // read flash: addr16, n8 (0 = 256)
+			std::uint16_t address = rx16();
+			send_flash(address, link::rx());
+			break;
+		}
+		case 'W': // program one flash page: addr16, page bytes
+			program_flash(rx16());
+			break;
+		case 'r': { // read EEPROM: addr16, n8
+			std::uint16_t address = rx16();
+			send_eeprom(address, link::rx());
+			break;
+		}
+		case 'w': { // write EEPROM: addr16, n8, then n bytes each acked
+			std::uint16_t address = rx16();
+			store_eeprom(address, link::rx());
+			break;
+		}
+		case 'F': // fuse and lock bytes
+			send_fuses();
+			break;
+		case 'G': // hand over to the application
+			link::tx(ack);
+			run_app();
+		default: // unknown bytes are ignored; the loop re-acks
+			break;
+		}
+	}
+}
+
+} // namespace
+} // namespace pureboot
+
+template struct avr::startup::entry<pureboot::run>;

pureboot/pureboot.py

@@ -0,0 +1,450 @@
+#!/usr/bin/env python3
+"""pureboot host tool — the smart half of the pureboot protocol (README.md).
+
+The device exposes primitives; this tool composes them: image loading (raw
+binary or Intel HEX), flash programming with read-back verification, erase as
+writing 0xff, EEPROM programming, fuse and info readout, activation-timeout
+configuration, and — on chips without a hardware boot section — the
+reset-vector surgery that re-homes the application's entry through the
+trampoline word below the loader, writing page 0 last so an interrupted
+flash still falls through to the loader.
+
+Python standard library only; the serial port is driven with termios, so any
+tty works — a USB adapter as well as a simavr pty.
+"""
+
+import argparse
+import os
+import select
+import sys
+import termios
+import time
+
+PROMPT = b"+"
+PROTOCOL_VERSION = 1
+
+
+class Error(Exception):
+    pass
+
+
+# ---------------------------------------------------------------- serial ---
+
+
+class Port:
+    """A raw serial port with deadline-based reads."""
+
+    def __init__(self, path, baud):
+        self.fd = os.open(path, os.O_RDWR | os.O_NOCTTY)
+        attrs = termios.tcgetattr(self.fd)
+        attrs[0] = 0  # iflag
+        attrs[1] = 0  # oflag
+        attrs[2] = termios.CREAD | termios.CLOCAL | termios.CS8  # cflag
+        attrs[3] = 0  # lflag
+        try:
+            speed = getattr(termios, f"B{baud}")
+        except AttributeError:
+            raise Error(f"unsupported baud rate {baud}") from None
+        attrs[4] = attrs[5] = speed
+        attrs[6][termios.VMIN] = 0
+        attrs[6][termios.VTIME] = 0
+        termios.tcsetattr(self.fd, termios.TCSANOW, attrs)
+
+    def close(self):
+        os.close(self.fd)
+
+    def write(self, data):
+        os.write(self.fd, data)
+
+    def flush_input(self):
+        termios.tcflush(self.fd, termios.TCIFLUSH)
+
+    def read_available(self, wait):
+        """Everything that arrives within `wait` seconds of quiet start."""
+        ready, _, _ = select.select([self.fd], [], [], wait)
+        return os.read(self.fd, 4096) if ready else b""
+
+    def read_exact(self, count, timeout):
+        data = b""
+        deadline = time.monotonic() + timeout
+        while len(data) < count:
+            remaining = deadline - time.monotonic()
+            if remaining <= 0:
+                raise Error(f"timeout: got {len(data)} of {count} bytes")
+            ready, _, _ = select.select([self.fd], [], [], remaining)
+            if ready:
+                data += os.read(self.fd, count - len(data))
+        return data
+
+
+# -------------------------------------------------------------- protocol ---
+
+
+class Info:
+    """The 12-byte info block."""
+
+    def __init__(self, raw):
+        if len(raw) != 12 or raw[0:2] != b"PB":
+            raise Error(f"bad info block: {raw.hex()}")
+        if raw[2] != PROTOCOL_VERSION:
+            raise Error(f"protocol version {raw[2]}, tool speaks {PROTOCOL_VERSION}")
+        self.signature = raw[3:6]
+        self.page = raw[6]
+        self.base = raw[7] | (raw[8] << 8)
+        self.eeprom_size = raw[9] | (raw[10] << 8)
+        self.patch_vector = bool(raw[11] & 1)
+        self.flash_size = self.base + 512
+
+    def describe(self):
+        sig = " ".join(f"{b:02x}" for b in self.signature)
+        vector = "host-patched reset vector" if self.patch_vector else "hardware boot section"
+        return (
+            f"signature {sig}, page {self.page} B, "
+            f"app flash {self.base} B (loader at {self.base:#06x}), "
+            f"EEPROM {self.eeprom_size} B, {vector}"
+        )
+
+
+class Loader:
+    """A pureboot session. Between commands the loader has prompted `+` and
+    awaits a command byte; every method restores that invariant."""
+
+    def __init__(self, port):
+        self.port = port
+        self.info = None
+
+    def connect(self, wait):
+        """Knock until the activation window answers, then read the info
+        block. Also converges when the loader already sits in its command
+        loop: the knock bytes are ignored-or-executed there, and the drain
+        absorbs whatever they produced."""
+        self.port.flush_input()
+        deadline = time.monotonic() + wait
+        while True:
+            self.port.write(b"pb")
+            if PROMPT in self.port.read_available(0.4):
+                break
+            if time.monotonic() > deadline:
+                raise Error("no answer — reset the device within its activation window")
+        while self.port.read_available(0.3):
+            pass
+        self.port.write(b"b")
+        self.info = Info(self.port.read_exact(12, 2.0))
+        self._expect_prompt()
+        return self.info
+
+    def _expect_prompt(self, timeout=2.0):
+        byte = self.port.read_exact(1, timeout)
+        if byte != PROMPT:
+            raise Error(f"expected prompt, got {byte.hex()}")
+
+    def _command(self, tx, reply_len=0, timeout=2.0):
+        self.port.write(tx)
+        reply = self.port.read_exact(reply_len, timeout) if reply_len else b""
+        self._expect_prompt(timeout)
+        return reply
+
+    def _stream_read(self, command, address, count):
+        data = b""
+        while count:
+            chunk = min(count, 256)
+            head = bytes((ord(command), address & 0xFF, address >> 8, chunk & 0xFF))
+            data += self._command(head, chunk, 5.0)
+            address += chunk
+            count -= chunk
+        return data
+
+    def read_flash(self, address, count):
+        return self._stream_read("R", address, count)
+
+    def read_eeprom(self, address, count):
+        return self._stream_read("r", address, count)
+
+    def write_page(self, address, data):
+        assert len(data) == self.info.page and address % self.info.page == 0
+        head = bytes((ord("W"), address & 0xFF, address >> 8))
+        self._command(head + data, 0, 2.0)
+
+    def write_eeprom(self, address, data):
+        offset = 0
+        while offset < len(data):
+            chunk = data[offset : offset + 256]
+            head = bytes((ord("w"), address & 0xFF, address >> 8, len(chunk) & 0xFF))
+            self.port.write(head)
+            for byte in chunk:
+                self.port.write(bytes((byte,)))
+                self._expect_prompt()  # per-byte ack: the write has begun
+            self._expect_prompt()  # the next command prompt
+            address += len(chunk)
+            offset += len(chunk)
+
+    def read_fuses(self):
+        return self._command(b"F", 4, 2.0)
+
+    def run_application(self):
+        self.port.write(b"G")
+        self._expect_prompt()
+
+
+# ---------------------------------------------------------------- images ---
+
+
+def load_image(path):
+    """Raw binary, or Intel HEX by extension (.hex/.ihx/.ihex)."""
+    data = open(path, "rb").read()
+    if not path.lower().endswith((".hex", ".ihx", ".ihex")):
+        if not data:
+            raise Error(f"{path}: empty image")
+        return data
+    memory = {}
+    for number, line in enumerate(data.decode("ascii", "replace").splitlines(), 1):
+        line = line.strip()
+        if not line:
+            continue
+        if not line.startswith(":"):
+            raise Error(f"{path}:{number}: not an Intel HEX record")
+        record = bytes.fromhex(line[1:])
+        if sum(record) & 0xFF:
+            raise Error(f"{path}:{number}: checksum mismatch")
+        count, address, kind = record[0], (record[1] << 8) | record[2], record[3]
+        payload = record[4 : 4 + count]
+        if kind == 0:
+            for i, byte in enumerate(payload):
+                memory[address + i] = byte
+        elif kind == 1:
+            break
+        elif kind in (2, 4) and not any(payload):
+            continue  # a zero base extends nothing
+        elif kind in (3, 5):
+            continue  # start address: irrelevant, reset is the entry
+        else:
+            raise Error(f"{path}:{number}: record type {kind} reaches beyond the 16-bit space")
+    if not memory:
+        raise Error(f"{path}: empty image")
+    return bytes(memory.get(i, 0xFF) for i in range(max(memory) + 1))
+
+
+# --------------------------------------------------------------- surgery ---
+
+
+def rjmp_target(word_address, opcode, flash_words):
+    return (word_address + 1 + (opcode & 0x0FFF)) % flash_words
+
+
+def rjmp_to(word_address, destination, flash_words):
+    return 0xC000 | ((destination - word_address - 1) % flash_words % 0x1000)
+
+
+def plan_flash(image, info):
+    """The pages to program, as {page_address: bytes}, already carrying the
+    reset-vector surgery where the chip needs it. Page 0 must go last —
+    callers get it separated."""
+    page = info.page
+    limit = info.base - (2 if info.patch_vector else 0)
+    if len(image) > limit:
+        raise Error(f"image is {len(image)} B, application flash ends at {limit}")
+    final = bytearray(image) + bytearray([0xFF] * (-len(image) % page))
+
+    if info.patch_vector:
+        flash_words = info.flash_size // 2
+        word0 = final[0] | (final[1] << 8)
+        if word0 & 0xF000 != 0xC000:
+            raise Error(
+                "the image's reset vector is not an rjmp — pureboot's vector "
+                "surgery cannot re-home it (crt-less entry at address 0?)"
+            )
+        entry = rjmp_target(0, word0, flash_words)
+        if entry >= info.base // 2:
+            raise Error(
+                "the image's reset vector already targets the loader — this "
+                "is a read-back of a patched image; flash the original"
+            )
+        trampoline_word = (info.base - 2) // 2
+        patch = rjmp_to(0, info.base // 2, flash_words)
+        final[0], final[1] = patch & 0xFF, patch >> 8
+        trampoline_page = info.base - page
+        if len(final) < trampoline_page + page:
+            final += bytearray([0xFF] * (trampoline_page + page - len(final)))
+        jump = rjmp_to(trampoline_word, entry, flash_words)
+        final[info.base - 2], final[info.base - 1] = jump & 0xFF, jump >> 8
+
+    pages = {a: bytes(final[a : a + page]) for a in range(0, len(final), page)}
+    return pages
+
+
+def covered(pages, skip_blank):
+    """Pages in programming order: ascending, page 0 last; optionally
+    dropping all-0xff pages (sound only over erased flash) — never the
+    load-bearing page 0."""
+    rest = [a for a in sorted(pages) if a != 0]
+    if skip_blank:
+        rest = [a for a in rest if pages[a].count(0xFF) != len(pages[a])]
+    return rest + [0]
+
+
+# ------------------------------------------------------------ operations ---
+
+
+def op_erase_flash(loader):
+    """0xff over the whole application area. Order does not matter here —
+    every target byte is the same value — and a blank word 0 still falls
+    through to the loader, so an interruption is harmless."""
+    blank = bytes([0xFF] * loader.info.page)
+    for address in range(0, loader.info.base, loader.info.page):
+        loader.write_page(address, blank)
+    print(f"erase: {loader.info.base // loader.info.page} pages")
+
+
+def op_erase_eeprom(loader):
+    loader.write_eeprom(0, bytes([0xFF] * loader.info.eeprom_size))
+    print(f"erase: {loader.info.eeprom_size} B of EEPROM")
+
+
+def op_flash(loader, path, erase, verify):
+    image = load_image(path)
+    pages = plan_flash(image, loader.info)
+    if erase:
+        op_erase_flash(loader)
+    order = covered(pages, skip_blank=erase)
+    for address in order:
+        loader.write_page(address, pages[address])
+    print(f"flash: {path}: {len(order)} pages")
+    if verify:
+        verify_pages(loader, pages)
+
+
+def verify_pages(loader, pages):
+    for address in sorted(pages):
+        got = loader.read_flash(address, loader.info.page)
+        if got != pages[address]:
+            first = next(i for i in range(len(got)) if got[i] != pages[address][i])
+            raise Error(
+                f"verify failed at {address + first:#06x}: "
+                f"wrote {pages[address][first]:02x}, read {got[first]:02x}"
+            )
+    print(f"verify: {len(pages)} pages ok")
+
+
+def op_verify_flash(loader, path):
+    verify_pages(loader, plan_flash(load_image(path), loader.info))
+
+
+def op_read_flash(loader, path):
+    data = loader.read_flash(0, loader.info.base)
+    open(path, "wb").write(data)
+    print(f"read flash: {len(data)} B -> {path}")
+
+
+def op_eeprom(loader, path, erase, verify):
+    image = load_image(path)
+    if len(image) > loader.info.eeprom_size:
+        raise Error(f"EEPROM image is {len(image)} B, device has {loader.info.eeprom_size}")
+    if erase:
+        op_erase_eeprom(loader)
+    loader.write_eeprom(0, image)
+    print(f"eeprom: {path}: {len(image)} B")
+    if verify:
+        got = loader.read_eeprom(0, len(image))
+        if got != image:
+            first = next(i for i in range(len(got)) if got[i] != image[i])
+            raise Error(f"verify failed at EEPROM {first:#06x}: wrote {image[first]:02x}, read {got[first]:02x}")
+        print(f"verify: {len(image)} B ok")
+
+
+def op_verify_eeprom(loader, path):
+    image = load_image(path)
+    got = loader.read_eeprom(0, len(image))
+    if got != image:
+        first = next(i for i in range(len(got)) if got[i] != image[i])
+        raise Error(f"verify failed at EEPROM {first:#06x}: expected {image[first]:02x}, read {got[first]:02x}")
+    print(f"verify: {len(image)} B of EEPROM ok")
+
+
+def op_read_eeprom(loader, path):
+    data = loader.read_eeprom(0, loader.info.eeprom_size)
+    open(path, "wb").write(data)
+    print(f"read EEPROM: {len(data)} B -> {path}")
+
+
+def op_timeout(loader, seconds):
+    loader.write_eeprom(loader.info.eeprom_size - 1, bytes((seconds,)))
+    label = f"{seconds} s" if seconds else "the device default"
+    print(f"activation timeout: {label}")
+
+
+def op_fuses(loader):
+    low, lock, extended, high = loader.read_fuses()
+    print(f"fuses: low {low:02x} high {high:02x} extended {extended:02x} lock {lock:02x}")
+
+
+# -------------------------------------------------------------------- cli ---
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="pureboot host tool", epilog="operations run in the order listed above"
+    )
+    parser.add_argument("--port", required=True, help="serial device (or simavr pty)")
+    parser.add_argument("--baud", type=int, default=115200, help="115200 mega, 57600 tinies")
+    parser.add_argument("--wait", type=float, default=30.0, help="seconds to keep knocking")
+    parser.add_argument("--info", action="store_true", help="print the device info block")
+    parser.add_argument("--fuses", action="store_true", help="read the fuse and lock bytes")
+    parser.add_argument("--erase-flash", action="store_true", help="0xff over the application flash")
+    parser.add_argument("--flash", metavar="FILE", help="program an application (bin or ihex)")
+    parser.add_argument("--no-verify", action="store_true", help="skip read-back after writes")
+    parser.add_argument("--read-flash", metavar="FILE", help="dump the application flash")
+    parser.add_argument("--verify-flash", metavar="FILE", help="compare flash against an image")
+    parser.add_argument("--erase-eeprom", action="store_true", help="0xff over the EEPROM")
+    parser.add_argument("--eeprom", metavar="FILE", help="program the EEPROM (bin or ihex)")
+    parser.add_argument("--read-eeprom", metavar="FILE", help="dump the EEPROM")
+    parser.add_argument("--verify-eeprom", metavar="FILE", help="compare EEPROM against an image")
+    parser.add_argument("--timeout", type=int, metavar="S", help="activation window, 1-254 s (0: default)")
+    parser.add_argument("--stay", action="store_true", help="leave the loader in its session")
+    args = parser.parse_args()
+
+    if args.timeout is not None and not 0 <= args.timeout <= 254:
+        parser.error("--timeout must be 0..254 (255 is the erased cell)")
+
+    port = Port(args.port, args.baud)
+    try:
+        loader = Loader(port)
+        info = loader.connect(args.wait)
+        if args.info:
+            print(f"device: {info.describe()}")
+        if args.fuses:
+            op_fuses(loader)
+        if args.flash:
+            op_flash(loader, args.flash, args.erase_flash, not args.no_verify)
+        elif args.erase_flash:
+            op_erase_flash(loader)
+        if args.read_flash:
+            op_read_flash(loader, args.read_flash)
+        if args.verify_flash:
+            op_verify_flash(loader, args.verify_flash)
+        if args.eeprom:
+            op_eeprom(loader, args.eeprom, args.erase_eeprom, not args.no_verify)
+        elif args.erase_eeprom:
+            op_erase_eeprom(loader)
+        if args.read_eeprom:
+            op_read_eeprom(loader, args.read_eeprom)
+        if args.verify_eeprom:
+            op_verify_eeprom(loader, args.verify_eeprom)
+        if args.timeout is not None:
+            op_timeout(loader, args.timeout)
+        if args.stay:
+            print("loader stays in its session (reset to leave)")
+        else:
+            loader.run_application()
+            print("application running")
+    finally:
+        port.close()
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except Error as error:
+        print(f"error: {error}", file=sys.stderr)
+        sys.exit(1)
+    except KeyboardInterrupt:
+        sys.exit(130)

stk500v2/clock.hpp

@@ -1,5 +0,0 @@
-#pragma once
-
-//#define F_CPU 18'432'000
-#define F_CPU 16'000'000
-#include <util/delay.h>

stk500v2/command.hpp

@@ -1,113 +0,0 @@
-#pragma once
-
-#include <stdint.h>
-
-//////////////////////////////////////////////////////////////////////////
-// STK message constants
-
-static constexpr uint8_t MESSAGE_START = 0x1B; // ASCII ESC
-static constexpr uint8_t TOKEN = 0x0E;
-
-//////////////////////////////////////////////////////////////////////////
-// STK general command constants
-
-static constexpr uint8_t CMD_SIGN_ON = 0x01;
-static constexpr uint8_t CMD_SET_PARAMETER = 0x02;
-static constexpr uint8_t CMD_GET_PARAMETER = 0x03;
-static constexpr uint8_t CMD_SET_DEVICE_PARAMETERS = 0x04;
-static constexpr uint8_t CMD_OSCCAL = 0x05;
-static constexpr uint8_t CMD_LOAD_ADDRESS = 0x06;
-static constexpr uint8_t CMD_FIRMWARE_UPGRADE = 0x07;
-
-//////////////////////////////////////////////////////////////////////////
-// STK ISP command constants
-
-static constexpr uint8_t CMD_ENTER_PROGMODE_ISP = 0x10;
-static constexpr uint8_t CMD_LEAVE_PROGMODE_ISP = 0x11;
-static constexpr uint8_t CMD_CHIP_ERASE_ISP = 0x12;
-static constexpr uint8_t CMD_PROGRAM_FLASH_ISP = 0x13;
-static constexpr uint8_t CMD_READ_FLASH_ISP = 0x14;
-static constexpr uint8_t CMD_PROGRAM_EEPROM_ISP = 0x15;
-static constexpr uint8_t CMD_READ_EEPROM_ISP = 0x16;
-static constexpr uint8_t CMD_PROGRAM_FUSE_ISP = 0x17;
-static constexpr uint8_t CMD_READ_FUSE_ISP = 0x18;
-static constexpr uint8_t CMD_PROGRAM_LOCK_ISP = 0x19;
-static constexpr uint8_t CMD_READ_LOCK_ISP = 0x1A;
-static constexpr uint8_t CMD_READ_SIGNATURE_ISP = 0x1B;
-static constexpr uint8_t CMD_READ_OSCCAL_ISP = 0x1C;
-static constexpr uint8_t CMD_SPI_MULTI = 0x1D;
-
-//////////////////////////////////////////////////////////////////////////
-// STK PP command constants
-
-static constexpr uint8_t CMD_ENTER_PROGMODE_PP = 0x20;
-static constexpr uint8_t CMD_LEAVE_PROGMODE_PP = 0x21;
-static constexpr uint8_t CMD_CHIP_ERASE_PP = 0x22;
-static constexpr uint8_t CMD_PROGRAM_FLASH_PP = 0x23;
-static constexpr uint8_t CMD_READ_FLASH_PP = 0x24;
-static constexpr uint8_t CMD_PROGRAM_EEPROM_PP = 0x25;
-static constexpr uint8_t CMD_READ_EEPROM_PP = 0x26;
-static constexpr uint8_t CMD_PROGRAM_FUSE_PP = 0x27;
-static constexpr uint8_t CMD_READ_FUSE_PP = 0x28;
-static constexpr uint8_t CMD_PROGRAM_LOCK_PP = 0x29;
-static constexpr uint8_t CMD_READ_LOCK_PP = 0x2A;
-static constexpr uint8_t CMD_READ_SIGNATURE_PP = 0x2B;
-static constexpr uint8_t CMD_READ_OSCCAL_PP = 0x2C;
-
-static constexpr uint8_t CMD_SET_CONTROL_STACK = 0x2D;
-
-//////////////////////////////////////////////////////////////////////////
-// STK HVSP command constants
-
-static constexpr uint8_t CMD_ENTER_PROGMODE_HVSP = 0x30;
-static constexpr uint8_t CMD_LEAVE_PROGMODE_HVSP = 0x31;
-static constexpr uint8_t CMD_CHIP_ERASE_HVSP = 0x32;
-static constexpr uint8_t CMD_PROGRAM_FLASH_HVSP = 0x33;
-static constexpr uint8_t CMD_READ_FLASH_HVSP = 0x34;
-static constexpr uint8_t CMD_PROGRAM_EEPROM_HVSP = 0x35;
-static constexpr uint8_t CMD_READ_EEPROM_HVSP = 0x36;
-static constexpr uint8_t CMD_PROGRAM_FUSE_HVSP = 0x37;
-static constexpr uint8_t CMD_READ_FUSE_HVSP = 0x38;
-static constexpr uint8_t CMD_PROGRAM_LOCK_HVSP = 0x39;
-static constexpr uint8_t CMD_READ_LOCK_HVSP = 0x3A;
-static constexpr uint8_t CMD_READ_SIGNATURE_HVSP = 0x3B;
-static constexpr uint8_t CMD_READ_OSCCAL_HVSP = 0x3C;
-
-//////////////////////////////////////////////////////////////////////////
-// STK status constants
-
-// Success
-static constexpr uint8_t STATUS_CMD_OK = 0x00;
-
-// Warnings
-static constexpr uint8_t STATUS_CMD_TOUT = 0x80;
-static constexpr uint8_t STATUS_RDY_BSY_TOUT = 0x81;
-static constexpr uint8_t STATUS_SET_PARAM_MISSING = 0x82;
-
-// Errors
-static constexpr uint8_t STATUS_CMD_FAILED = 0xC0;
-static constexpr uint8_t STATUS_CKSUM_ERROR = 0xC1;
-static constexpr uint8_t STATUS_CMD_UNKNOWN = 0xC9;
-
-//////////////////////////////////////////////////////////////////////////
-// STK parameter constants
-static constexpr uint8_t PARAM_BUILD_NUMBER_LOW = 0x80;
-static constexpr uint8_t PARAM_BUILD_NUMBER_HIGH = 0x81;
-static constexpr uint8_t PARAM_HW_VER = 0x90;
-static constexpr uint8_t PARAM_SW_MAJOR = 0x91;
-static constexpr uint8_t PARAM_SW_MINOR = 0x92;
-static constexpr uint8_t PARAM_VTARGET = 0x94;
-static constexpr uint8_t PARAM_VADJUST = 0x95;
-static constexpr uint8_t PARAM_OSC_PSCALE = 0x96;
-static constexpr uint8_t PARAM_OSC_CMATCH = 0x97;
-static constexpr uint8_t PARAM_SCK_DURATION = 0x98;
-static constexpr uint8_t PARAM_TOPCARD_DETECT = 0x9A;
-static constexpr uint8_t PARAM_STATUS = 0x9C;
-static constexpr uint8_t PARAM_DATA = 0x9D;
-static constexpr uint8_t PARAM_RESET_POLARITY = 0x9E;
-static constexpr uint8_t PARAM_CONTROLLER_INIT = 0x9F;
-
-//////////////////////////////////////////////////////////////////////////
-// STK answer constants
-
-static constexpr uint8_t ANSWER_CKSUM_ERROR = 0xB0;

stk500v2/main.cpp

@@ -1,667 +0,0 @@
-#include "clock.hpp"
-
-#include "stk500v2.hpp"
-
-#include "uart/uart.hpp"
-
-#include <math.h>
-
-#include <avr/boot.h>
-#include <avr/interrupt.h>
-#include <avr/io.h>
-#include <avr/pgmspace.h>
-
-#include "command.hpp"
-
-static constexpr auto TIMEOUT = 5000;
-static constexpr auto BAUD_RATE = 115200;
-
-using uart_interface = uart::Hardware0<uart::Config<BAUD_RATE>, uart::Driven::BLOCKING>;
-uart::Uart<uart_interface> serial;
-
-struct Message {
-	uint8_t start;
-	uint8_t number;
-	uint16_t size;
-	uint8_t token;
-	uint8_t body[275];
-	uint8_t checksum;
-};
-
-static inline bool receiveByte(uint8_t &data, uint16_t &timeout)
-{
-	constexpr auto MICROSECOND = 1000.0 * 1000;
-	constexpr auto SYMBOL_SIZE = 9;
-	constexpr auto BYTE_DELAY_US = (SYMBOL_SIZE * MICROSECOND) / BAUD_RATE;
-	constexpr auto NUM_MS_DELAY_STEPS = static_cast<uint16_t>(round(1000 / BYTE_DELAY_US));
-	uint16_t msDelay = NUM_MS_DELAY_STEPS;
-
-	while (timeout) {
-		if (serial.rxByte(data)) {
-			timeout = TIMEOUT;
-			return true;
-		}
-
-		_delay_us(BYTE_DELAY_US);
-
-		if (--msDelay == 0) {
-			msDelay = NUM_MS_DELAY_STEPS;
-			--timeout;
-		}
-	}
-
-	return false;
-}
-
-static inline uint8_t calcChecksum(const Message &msg)
-{
-	uint8_t checksum = msg.start;
-
-	for (uint16_t i = 1; i < 5 + msg.size; ++i) {
-		checksum ^= *(reinterpret_cast<const uint8_t *>(&msg) + i);
-	}
-
-	return checksum;
-}
-
-static inline bool receiveMessage(Message &msg, uint16_t &timeout)
-{
-	if (!receiveByte(msg.start, timeout) || msg.start != MESSAGE_START)
-		return false;
-	if (!receiveByte(msg.number, timeout))
-		return false;
-	if (!receiveByte(*(reinterpret_cast<uint8_t *>(&msg.size) + 1), timeout))
-		return false;
-	if (!receiveByte(*reinterpret_cast<uint8_t *>(&msg.size), timeout) || msg.size > sizeof(msg.body))
-		return false;
-	if (!receiveByte(msg.token, timeout) || msg.token != TOKEN)
-		return false;
-	for (uint16_t i = 0; i < msg.size; ++i) {
-		if (!receiveByte(msg.body[i], timeout))
-			return false;
-	}
-	if (!receiveByte(msg.checksum, timeout) || msg.checksum != calcChecksum(msg))
-		return false;
-
-	return true;
-}
-
-static inline void transmitMessage(const Message &msg)
-{
-	serial.txByte(msg.start);
-	serial.txByte(msg.number);
-	serial.txByte(msg.size >> 8);
-	serial.txByte(msg.size & 0xFF);
-	serial.txByte(msg.token);
-	for (uint16_t i = 0; i < msg.size; ++i)
-		serial.txByte(msg.body[i]);
-	serial.txByte(msg.checksum);
-}
-
-static inline bool isSignOn(const Message &msg)
-{
-	if (msg.size == 1 && msg.body[0] == CMD_SIGN_ON)
-		return true;
-	return false;
-}
-
-static inline bool isGetParameter(const Message &msg)
-{
-	if (msg.size == 2 && msg.body[0] == CMD_GET_PARAMETER)
-		return true;
-	return false;
-}
-
-static inline bool isSetParameter(const Message &msg)
-{
-	if (msg.size == 3 && msg.body[0] == CMD_SET_PARAMETER)
-		return true;
-	return false;
-}
-
-static inline bool isEnterProgmodeIsp(const Message &msg)
-{
-	if (msg.size == 12 && msg.body[0] == CMD_ENTER_PROGMODE_ISP)
-		return true;
-	return false;
-}
-
-static inline bool isReadSignatureIsp(const Message &msg)
-{
-	if (msg.size == 6 && msg.body[0] == CMD_READ_SIGNATURE_ISP)
-		return true;
-	return false;
-}
-
-static inline bool isReadFuseIsp(const Message &msg)
-{
-	if (msg.size == 6 && msg.body[0] == CMD_READ_FUSE_ISP)
-		return true;
-	return false;
-}
-
-static inline bool isReadLockIsp(const Message &msg)
-{
-	if (msg.size == 6 && msg.body[0] == CMD_READ_LOCK_ISP)
-		return true;
-	return false;
-}
-
-static inline bool isLoadAddress(const Message &msg)
-{
-	if (msg.size == 5 && msg.body[0] == CMD_LOAD_ADDRESS)
-		return true;
-	return false;
-}
-
-static inline bool isReadFlashIsp(const Message &msg)
-{
-	if (msg.size == 4 && msg.body[0] == CMD_READ_FLASH_ISP)
-		return true;
-	return false;
-}
-
-static inline bool isReadEepromIsp(const Message &msg)
-{
-	if (msg.size == 4 && msg.body[0] == CMD_READ_EEPROM_ISP)
-		return true;
-	return false;
-}
-
-static inline bool isChipEraseIsp(const Message &msg)
-{
-	if (msg.size == 7 && msg.body[0] == CMD_CHIP_ERASE_ISP)
-		return true;
-	return false;
-}
-
-static inline bool isProgramFlashIsp(const Message &msg)
-{
-	if (msg.body[0] == CMD_PROGRAM_FLASH_ISP) {
-		const auto dataSize = static_cast<uint16_t>(msg.body[1]) << 8 | msg.body[2];
-		if (msg.size == (dataSize + 10) && dataSize == SPM_PAGESIZE)
-			return true;
-	}
-	return false;
-}
-
-static inline bool isProgramEepromIsp(const Message &msg)
-{
-	if (msg.body[0] == CMD_PROGRAM_EEPROM_ISP) {
-		if (msg.size == (static_cast<uint16_t>(msg.body[1]) << 8 | msg.body[2]) + 10)
-			return true;
-	}
-
-	return false;
-}
-
-static inline bool isLeaveProgmodeIsp(const Message &msg)
-{
-	if (msg.size == 3 && msg.body[0] == CMD_LEAVE_PROGMODE_ISP)
-		return true;
-	return false;
-}
-
-static inline void formatSignOnAnswer(Message &msg)
-{
-	msg.size = 3 + 8;
-	msg.body[1] = STATUS_CMD_OK;
-	msg.body[2] = 8;
-	msg.body[3] = 'S';
-	msg.body[4] = 'T';
-	msg.body[5] = 'K';
-	msg.body[6] = '5';
-	msg.body[7] = '0';
-	msg.body[8] = '0';
-	msg.body[9] = '_';
-	msg.body[10] = '2';
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatGetParameterAnswer(Message &msg)
-{
-	msg.size = 3;
-
-	if (msg.body[1] == PARAM_HW_VER) {
-		msg.body[2] = 1;
-	} else if (msg.body[1] == PARAM_SW_MAJOR) {
-		msg.body[2] = 0x02;
-	} else if (msg.body[1] == PARAM_SW_MINOR) {
-		msg.body[2] = 0x0a;
-	} else if (msg.body[1] == PARAM_SCK_DURATION) {
-		msg.body[2] = 2;
-	} else if (msg.body[1] == PARAM_VADJUST) {
-		msg.body[2] = 25;
-	} else if (msg.body[1] == PARAM_VTARGET) {
-		msg.body[2] = 49;
-	} else if (msg.body[1] == PARAM_OSC_PSCALE) {
-		msg.body[2] = 2;
-	} else if (msg.body[1] == PARAM_OSC_CMATCH) {
-		msg.body[2] = 127;
-	} else if (msg.body[1] == PARAM_TOPCARD_DETECT) {
-		msg.body[2] = 0xFF;
-	} else {
-		msg.size = 2;
-	}
-
-	if (msg.size == 2) {
-		msg.body[1] = STATUS_CMD_FAILED;
-	} else {
-		msg.body[1] = STATUS_CMD_OK;
-	}
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatSetParameterAnswer(Message &msg)
-{
-	msg.size = 2;
-	msg.body[1] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatEnterProgmodeIspAnswer(Message &msg)
-{
-	msg.size = 2;
-	msg.body[1] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatReadSignatureIspAnswer(Message &msg)
-{
-	msg.size = 4;
-	msg.body[2] = boot_signature_byte_get(msg.body[4] * 2);
-	msg.body[1] = STATUS_CMD_OK;
-	msg.body[3] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatReadFuseIspAnswer(Message &msg)
-{
-	constexpr auto READ_LOW_FUSE_BITS = 0x0050;
-	constexpr auto READ_HIGH_FUSE_BITS = 0x0858;
-	constexpr auto READ_EXTENDED_FUSE_BITS = 0x0850;
-
-	msg.size = 4;
-
-	if (*reinterpret_cast<uint16_t *>(msg.body + 2) == READ_EXTENDED_FUSE_BITS) {
-		msg.body[2] = boot_lock_fuse_bits_get(GET_EXTENDED_FUSE_BITS);
-	}
-	if (*reinterpret_cast<uint16_t *>(msg.body + 2) == READ_HIGH_FUSE_BITS) {
-		msg.body[2] = boot_lock_fuse_bits_get(GET_HIGH_FUSE_BITS);
-	}
-	if (*reinterpret_cast<uint16_t *>(msg.body + 2) == READ_LOW_FUSE_BITS) {
-		msg.body[2] = boot_lock_fuse_bits_get(GET_LOW_FUSE_BITS);
-	}
-
-	msg.body[1] = STATUS_CMD_OK;
-	msg.body[3] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatReadLockIspAnswer(Message &msg)
-{
-	msg.size = 4;
-	msg.body[2] = boot_lock_fuse_bits_get(GET_LOCK_BITS);
-	msg.body[1] = STATUS_CMD_OK;
-	msg.body[3] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatLoadAddressAnswer(Message &msg)
-{
-	msg.size = 2;
-	msg.body[1] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatReadFlashIspAnswer(Message &msg, uint32_t &addr)
-{
-	const uint16_t byteAddress = 2 * addr;
-	const uint16_t numBytes = static_cast<uint16_t>(msg.body[1]) << 8 | msg.body[2];
-	msg.size = 3 + numBytes;
-	msg.body[1] = STATUS_CMD_OK;
-	for (uint16_t i = 0; i < numBytes; ++i) {
-		msg.body[i + 2] = pgm_read_byte(static_cast<uint16_t>(byteAddress + i));
-	}
-	const auto numWords = numBytes / 2;
-	addr += numWords;
-	msg.body[numBytes + 2] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-namespace {
-
-bool isEepromReady()
-{
-	return (EECR & (1 << EEPE)) ? false : true;
-}
-
-void waitEepromReady()
-{
-	while (!isEepromReady())
-		;
-}
-
-uint8_t readEepromByte(const uint8_t *addr)
-{
-	EEAR = reinterpret_cast<uint16_t>(addr);
-	EECR |= (1 << EERE);
-	return EEDR;
-}
-
-void writeEepromByte(uint8_t *addr, uint8_t value)
-{
-	EECR = 0;
-	EEAR = reinterpret_cast<uint16_t>(addr);
-	EEDR = value;
-	EECR |= (1 << EEMPE);
-	EECR |= (1 << EEPE);
-}
-
-//////////////////////////////////////////////////////////////////////////
-
-void writeFlashPage(uint32_t pageAddress, const uint8_t *data)
-{
-	boot_page_erase(pageAddress);
-	boot_spm_busy_wait();
-
-	for (uint16_t i = 0; i < SPM_PAGESIZE; i += 2) {
-		uint16_t dataWord = *data++;
-		dataWord |= (*data++) << 8;
-		boot_page_fill(pageAddress + i, dataWord);
-	}
-
-	boot_page_write(pageAddress);
-	boot_spm_busy_wait();
-	boot_rww_enable();
-}
-
-} // namespace
-
-static inline uint16_t getBootloaderSize()
-{
-	const auto highFuse = boot_lock_fuse_bits_get(GET_HIGH_FUSE_BITS);
-	constexpr auto BOOTSZ0 = 1;
-	constexpr auto BOOTSZ1 = 2;
-
-	if (highFuse & (1 << BOOTSZ1) && highFuse & (1 << BOOTSZ0))
-		return 256 * 2;
-	else if (highFuse & (1 << BOOTSZ1))
-		return 512 * 2;
-	else if (highFuse & (1 << BOOTSZ0))
-		return 1024 * 2;
-	return 2048 * 2;
-}
-
-static inline uint32_t getFlashSize()
-{
-	const auto bootloaderSize = getBootloaderSize();
-	return (FLASHEND - bootloaderSize + 1);
-}
-
-static inline void performChipErase(uint16_t flashStartAddress = 0x0000)
-{
-	constexpr auto getEepromEraseFuseBit = []() -> bool {
-		constexpr auto EESAVE = 3;
-		return boot_lock_fuse_bits_get(GET_HIGH_FUSE_BITS) & (1 << EESAVE);
-	};
-
-	constexpr auto eraseFlash = [](const uint16_t &flashStartAddress) {
-		const auto flashSize = getFlashSize();
-		const auto byteAddress = 2 * flashStartAddress;
-		for (uint16_t i = byteAddress; i < flashSize; i += SPM_PAGESIZE) {
-			boot_page_erase(i);
-			boot_spm_busy_wait();
-		}
-		boot_rww_enable();
-	};
-
-	constexpr auto eraseEeprom = [getEepromEraseFuseBit]() {
-		const auto eraseEeprom = getEepromEraseFuseBit();
-		if (eraseEeprom) {
-			constexpr auto EEPROM_SIZE = E2END + 1;
-			for (uint16_t i = 0; i < EEPROM_SIZE; ++i) {
-				writeEepromByte(reinterpret_cast<uint8_t *>(i), 0xFF);
-				waitEepromReady();
-			}
-		}
-	};
-
-	eraseFlash(flashStartAddress);
-	eraseEeprom();
-}
-
-static inline void formatChipEraseIspAnswer(Message &msg)
-{
-	msg.size = 2;
-	msg.body[1] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatReadEepromIspAnswer(Message &msg, uint32_t &addr)
-{
-	const uint16_t numBytes = static_cast<uint16_t>(msg.body[1]) << 8 | msg.body[2];
-	msg.size = 3 + numBytes;
-	msg.body[1] = STATUS_CMD_OK;
-	for (uint16_t i = 0; i < numBytes; ++i) {
-		msg.body[i + 2] = readEepromByte(reinterpret_cast<const uint8_t *>(addr + i));
-	}
-	addr += numBytes;
-	msg.body[numBytes + 2] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatProgramFlashIspAnswer(Message &msg, uint32_t &addr)
-{
-	const auto byteAddress = 2 * addr;
-	if (byteAddress < getFlashSize())
-		writeFlashPage(byteAddress, msg.body + 10);
-	const uint16_t numBytes = static_cast<uint16_t>(msg.body[1]) << 8 | msg.body[2];
-	const auto numWords = numBytes / 2;
-	addr += numWords;
-
-	msg.size = 2;
-	msg.body[1] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatProgramEepromIspAnswer(Message &msg, uint32_t &addr)
-{
-	const uint16_t numBytes = static_cast<uint16_t>(msg.body[1]) << 8 | msg.body[2];
-	for (uint16_t i = 0; i < numBytes; ++i) {
-		writeEepromByte(reinterpret_cast<uint8_t *>(addr + i), msg.body[10 + i]);
-		waitEepromReady();
-	}
-	addr += numBytes;
-	msg.size = 2;
-	msg.body[1] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatLeaveProgmodeIspAnswer(Message &msg)
-{
-	msg.size = 2;
-	msg.body[1] = STATUS_CMD_OK;
-
-	msg.checksum = calcChecksum(msg);
-}
-
-static inline void formatErrorAnswer(Message &msg)
-{
-	msg.start = MESSAGE_START;
-	msg.size = 1;
-	msg.token = TOKEN;
-	msg.body[0] = STATUS_CMD_UNKNOWN;
-	msg.checksum = calcChecksum(msg);
-}
-
-enum class ChipEraseState {
-	NONE = 0,
-	REQUEST = (1 << 1),
-	RESPONSE = (1 << 2),
-	PERFORM = REQUEST | RESPONSE,
-	PROGRAM = (1 << 3),
-	FINISH = REQUEST | RESPONSE | PROGRAM,
-};
-
-constexpr ChipEraseState operator|(const ChipEraseState &self, const ChipEraseState &other)
-{
-	return static_cast<ChipEraseState>(static_cast<uint8_t>(self) | static_cast<uint8_t>(other));
-}
-
-constexpr ChipEraseState &operator|=(ChipEraseState &self, const ChipEraseState &other)
-{
-	self = self | other;
-	return self;
-}
-
-static inline void handleMessage(Message &msg, uint32_t &addr, uint16_t &finishEraseAddress,
-                                 ChipEraseState &chipEraseFlag)
-{
-	if (isSignOn(msg))
-		formatSignOnAnswer(msg);
-	else if (isGetParameter(msg))
-		formatGetParameterAnswer(msg);
-	else if (isSetParameter(msg))
-		formatSetParameterAnswer(msg);
-	else if (isEnterProgmodeIsp(msg))
-		formatEnterProgmodeIspAnswer(msg);
-	else if (isReadSignatureIsp(msg))
-		formatReadSignatureIspAnswer(msg);
-	else if (isReadFuseIsp(msg))
-		formatReadFuseIspAnswer(msg);
-	else if (isReadLockIsp(msg))
-		formatReadLockIspAnswer(msg);
-	else if (isLoadAddress(msg)) {
-		addr = msg.body[1];
-		addr = (addr << 8) | msg.body[2];
-		addr = (addr << 8) | msg.body[3];
-		addr = (addr << 8) | msg.body[4];
-		formatLoadAddressAnswer(msg);
-	} else if (isReadFlashIsp(msg))
-		formatReadFlashIspAnswer(msg, addr);
-	else if (isReadEepromIsp(msg))
-		formatReadEepromIspAnswer(msg, addr);
-	else if (isChipEraseIsp(msg)) {
-		chipEraseFlag |= ChipEraseState::REQUEST;
-		formatChipEraseIspAnswer(msg);
-	} else if (isProgramFlashIsp(msg)) {
-		chipEraseFlag |= ChipEraseState::PROGRAM;
-		formatProgramFlashIspAnswer(msg, addr);
-		finishEraseAddress = addr;
-	} else if (isProgramEepromIsp(msg))
-		formatProgramEepromIspAnswer(msg, addr);
-	else if (isLeaveProgmodeIsp(msg)) {
-		chipEraseFlag |= ChipEraseState::RESPONSE;
-		formatLeaveProgmodeIspAnswer(msg);
-	} else
-		formatErrorAnswer(msg);
-
-	transmitMessage(msg);
-}
-
-static inline void interfaceTest()
-{
-	constexpr auto onSignOn = []() {};
-	constexpr auto onSetParam = []() {};
-	constexpr auto onGetParam = [](stk500v2::Param param, uint8_t &result) {
-		using stk500v2::Param;
-
-		switch (param) {
-		case Param::HW_VER:
-			result = 1;
-			break;
-		case Param::SW_MAJOR:
-			result = 2;
-			break;
-		case Param::SW_MINOR:
-			result = 10;
-			break;
-		case Param::SCK_DURATION:
-			result = 2;
-			break;
-		case Param::VADJUST:
-			result = 25;
-			break;
-		case Param::VTARGET:
-			result = 49;
-			break;
-		case Param::OSC_PSCALE:
-			result = 2;
-			break;
-		case Param::OSC_CMATCH:
-			result = 127;
-			break;
-		case Param::TOPCARD_DETECT:
-			result = 0xFF;
-			break;
-		default:
-			return false;
-		}
-
-		return true;
-	};
-
-	constexpr auto callbacks = stk500v2::Callbacks<onSignOn, onSetParam, onGetParam>();
-
-	stk500v2::Stk500v2<uart_interface, TIMEOUT, callbacks> stk500;
-	stk500.init();
-
-	while (stk500.callback())
-		;
-}
-
-int main()
-{
-	/*interfaceTest();
-	return 0;*/
-
-	serial.init();
-
-	Message msg;
-	uint32_t addr = 0x0000;
-	uint16_t finishEraseAddress = 0x0000;
-	ChipEraseState chipEraseFlag = ChipEraseState::NONE;
-	uint16_t timeout = TIMEOUT;
-
-	while (true) {
-		if (receiveMessage(msg, timeout)) {
-			handleMessage(msg, addr, finishEraseAddress, chipEraseFlag);
-		}
-
-		if (timeout == 0) {
-			if (chipEraseFlag == ChipEraseState::PERFORM) {
-				performChipErase();
-				chipEraseFlag = ChipEraseState::NONE;
-			} else if (chipEraseFlag == ChipEraseState::FINISH) {
-				performChipErase(finishEraseAddress);
-				chipEraseFlag = ChipEraseState::NONE;
-			}
-
-			asm volatile("jmp 0x0000");
-		}
-	}
-
-	return 0;
-}
-
-void startup() __attribute__((naked, section(".vectors")));
-void startup()
-{
-	asm volatile("clr __zero_reg__");
-	SP = RAMEND;
-	SREG = 0;
-	asm volatile("jmp main");
-}

stk500v2/stk500v2.cppproj

@@ -1,275 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="14.0">
-  <PropertyGroup>
-    <SchemaVersion>2.0</SchemaVersion>
-    <ProjectVersion>7.0</ProjectVersion>
-    <ToolchainName>com.Atmel.AVRGCC8.CPP</ToolchainName>
-    <ProjectGuid>{19798cce-5d96-40e9-b769-d209715dce0c}</ProjectGuid>
-    <avrdevice>ATmega328P</avrdevice>
-    <avrdeviceseries>none</avrdeviceseries>
-    <OutputType>Executable</OutputType>
-    <Language>CPP</Language>
-    <OutputFileName>$(MSBuildProjectName)</OutputFileName>
-    <OutputFileExtension>.elf</OutputFileExtension>
-    <OutputDirectory>$(MSBuildProjectDirectory)\$(Configuration)</OutputDirectory>
-    <AssemblyName>stk500v2</AssemblyName>
-    <Name>stk500v2</Name>
-    <RootNamespace>stk500v2</RootNamespace>
-    <ToolchainFlavour>avr-g++-10.0.1</ToolchainFlavour>
-    <KeepTimersRunning>true</KeepTimersRunning>
-    <OverrideVtor>false</OverrideVtor>
-    <CacheFlash>true</CacheFlash>
-    <ProgFlashFromRam>true</ProgFlashFromRam>
-    <RamSnippetAddress>0x20000000</RamSnippetAddress>
-    <UncachedRange />
-    <preserveEEPROM>true</preserveEEPROM>
-    <OverrideVtorValue>exception_table</OverrideVtorValue>
-    <BootSegment>2</BootSegment>
-    <ResetRule>0</ResetRule>
-    <eraseonlaunchrule>0</eraseonlaunchrule>
-    <EraseKey />
-    <avrtool>com.atmel.avrdbg.tool.atmelice</avrtool>
-    <avrtoolserialnumber>J41800099437</avrtoolserialnumber>
-    <avrdeviceexpectedsignature>0x1E950F</avrdeviceexpectedsignature>
-    <com_atmel_avrdbg_tool_stk500>
-      <ToolOptions>
-        <InterfaceProperties>
-          <IspClock>125000</IspClock>
-        </InterfaceProperties>
-        <InterfaceName>ISP</InterfaceName>
-      </ToolOptions>
-      <ToolType>com.atmel.avrdbg.tool.stk500</ToolType>
-      <ToolNumber>
-      </ToolNumber>
-      <ToolName>STK500</ToolName>
-    </com_atmel_avrdbg_tool_stk500>
-    <avrtoolinterface>ISP</avrtoolinterface>
-    <avrtoolinterfaceclock>125000</avrtoolinterfaceclock>
-    <AsfFrameworkConfig>
-      <framework-data xmlns="">
-        <options />
-        <configurations />
-        <files />
-        <documentation help="" />
-        <offline-documentation help="" />
-        <dependencies>
-          <content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.47.0" />
-        </dependencies>
-      </framework-data>
-    </AsfFrameworkConfig>
-    <com_atmel_avrdbg_tool_atmelice>
-      <ToolOptions>
-        <InterfaceProperties>
-          <IspClock>125000</IspClock>
-        </InterfaceProperties>
-        <InterfaceName>ISP</InterfaceName>
-      </ToolOptions>
-      <ToolType>com.atmel.avrdbg.tool.atmelice</ToolType>
-      <ToolNumber>J41800099437</ToolNumber>
-      <ToolName>Atmel-ICE</ToolName>
-    </com_atmel_avrdbg_tool_atmelice>
-    <custom>
-      <ToolOptions>
-        <InterfaceProperties>
-          <IspClock>125000</IspClock>
-        </InterfaceProperties>
-        <InterfaceName>
-        </InterfaceName>
-      </ToolOptions>
-      <ToolType>custom</ToolType>
-      <ToolNumber>
-      </ToolNumber>
-      <ToolName>Custom Programming Tool</ToolName>
-    </custom>
-    <com_atmel_avrdbg_tool_simulator>
-      <ToolOptions xmlns="">
-        <InterfaceProperties>
-        </InterfaceProperties>
-        <InterfaceName>
-        </InterfaceName>
-      </ToolOptions>
-      <ToolType xmlns="">com.atmel.avrdbg.tool.simulator</ToolType>
-      <ToolNumber xmlns="">
-      </ToolNumber>
-      <ToolName xmlns="">Simulator</ToolName>
-    </com_atmel_avrdbg_tool_simulator>
-    <AAFDebugger>
-      <AAFDebugFiles>
-      </AAFDebugFiles>
-    </AAFDebugger>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
-    <ToolchainSettings>
-      <AvrGccCpp>
-        <avrgcc.common.Device>-mmcu=atmega328p</avrgcc.common.Device>
-        <avrgcc.common.outputfiles.hex>True</avrgcc.common.outputfiles.hex>
-        <avrgcc.common.outputfiles.lss>True</avrgcc.common.outputfiles.lss>
-        <avrgcc.common.outputfiles.eep>True</avrgcc.common.outputfiles.eep>
-        <avrgcc.common.outputfiles.srec>True</avrgcc.common.outputfiles.srec>
-        <avrgcc.common.outputfiles.usersignatures>False</avrgcc.common.outputfiles.usersignatures>
-        <avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcc.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>NDEBUG</Value>
-          </ListValues>
-        </avrgcc.compiler.symbols.DefSymbols>
-        <avrgcc.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcc.compiler.directories.IncludePaths>
-        <avrgcc.compiler.optimization.level>Optimize for size (-Os)</avrgcc.compiler.optimization.level>
-        <avrgcc.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcc.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcc.compiler.warnings.AllWarnings>True</avrgcc.compiler.warnings.AllWarnings>
-        <avrgcc.compiler.warnings.ExtraWarnings>True</avrgcc.compiler.warnings.ExtraWarnings>
-        <avrgcc.compiler.warnings.Pedantic>True</avrgcc.compiler.warnings.Pedantic>
-        <avrgcc.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -std=c11</avrgcc.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcccpp.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>NDEBUG</Value>
-          </ListValues>
-        </avrgcccpp.compiler.symbols.DefSymbols>
-        <avrgcccpp.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.compiler.directories.IncludePaths>
-        <avrgcccpp.compiler.optimization.level>Optimize for size (-Os)</avrgcccpp.compiler.optimization.level>
-        <avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcccpp.compiler.warnings.AllWarnings>True</avrgcccpp.compiler.warnings.AllWarnings>
-        <avrgcccpp.compiler.warnings.Pedantic>True</avrgcccpp.compiler.warnings.Pedantic>
-        <avrgcccpp.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -Wextra -std=c++20</avrgcccpp.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.linker.general.NoStartupOrDefaultLibs>True</avrgcccpp.linker.general.NoStartupOrDefaultLibs>
-        <avrgcccpp.linker.libraries.Libraries>
-          <ListValues>
-            <Value>libm</Value>
-          </ListValues>
-        </avrgcccpp.linker.libraries.Libraries>
-        <avrgcccpp.linker.memorysettings.Flash>
-          <ListValues>
-            <Value>.text=0x3C00</Value>
-          </ListValues>
-        </avrgcccpp.linker.memorysettings.Flash>
-        <avrgcccpp.assembler.general.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.assembler.general.IncludePaths>
-      </AvrGccCpp>
-    </ToolchainSettings>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
-    <ToolchainSettings>
-      <AvrGccCpp>
-        <avrgcc.common.Device>-mmcu=atmega328p</avrgcc.common.Device>
-        <avrgcc.common.outputfiles.hex>True</avrgcc.common.outputfiles.hex>
-        <avrgcc.common.outputfiles.lss>True</avrgcc.common.outputfiles.lss>
-        <avrgcc.common.outputfiles.eep>True</avrgcc.common.outputfiles.eep>
-        <avrgcc.common.outputfiles.srec>True</avrgcc.common.outputfiles.srec>
-        <avrgcc.common.outputfiles.usersignatures>False</avrgcc.common.outputfiles.usersignatures>
-        <avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcc.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcc.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcc.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>DEBUG</Value>
-          </ListValues>
-        </avrgcc.compiler.symbols.DefSymbols>
-        <avrgcc.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcc.compiler.directories.IncludePaths>
-        <avrgcc.compiler.optimization.level>Optimize (-O1)</avrgcc.compiler.optimization.level>
-        <avrgcc.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcc.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcc.compiler.optimization.DebugLevel>Maximum (-g3)</avrgcc.compiler.optimization.DebugLevel>
-        <avrgcc.compiler.warnings.AllWarnings>True</avrgcc.compiler.warnings.AllWarnings>
-        <avrgcc.compiler.warnings.ExtraWarnings>True</avrgcc.compiler.warnings.ExtraWarnings>
-        <avrgcc.compiler.warnings.Pedantic>True</avrgcc.compiler.warnings.Pedantic>
-        <avrgcc.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -std=c11</avrgcc.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultCharTypeUnsigned>
-        <avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>True</avrgcccpp.compiler.general.ChangeDefaultBitFieldUnsigned>
-        <avrgcccpp.compiler.symbols.DefSymbols>
-          <ListValues>
-            <Value>DEBUG</Value>
-          </ListValues>
-        </avrgcccpp.compiler.symbols.DefSymbols>
-        <avrgcccpp.compiler.directories.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.compiler.directories.IncludePaths>
-        <avrgcccpp.compiler.optimization.level>Optimize debugging experience (-Og)</avrgcccpp.compiler.optimization.level>
-        <avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>True</avrgcccpp.compiler.optimization.AllocateBytesNeededForEnum>
-        <avrgcccpp.compiler.optimization.DebugLevel>Maximum (-g3)</avrgcccpp.compiler.optimization.DebugLevel>
-        <avrgcccpp.compiler.warnings.AllWarnings>True</avrgcccpp.compiler.warnings.AllWarnings>
-        <avrgcccpp.compiler.warnings.Pedantic>True</avrgcccpp.compiler.warnings.Pedantic>
-        <avrgcccpp.compiler.miscellaneous.OtherFlags>-fno-threadsafe-statics -Wextra -std=c++20</avrgcccpp.compiler.miscellaneous.OtherFlags>
-        <avrgcccpp.linker.general.NoStartupOrDefaultLibs>True</avrgcccpp.linker.general.NoStartupOrDefaultLibs>
-        <avrgcccpp.linker.libraries.Libraries>
-          <ListValues>
-            <Value>libm</Value>
-          </ListValues>
-        </avrgcccpp.linker.libraries.Libraries>
-        <avrgcccpp.linker.memorysettings.Flash>
-          <ListValues>
-            <Value>.text=0x3800</Value>
-          </ListValues>
-        </avrgcccpp.linker.memorysettings.Flash>
-        <avrgcccpp.assembler.general.IncludePaths>
-          <ListValues>
-            <Value>%24(PackRepoDir)\Atmel\ATmega_DFP\1.4.346\include</Value>
-          </ListValues>
-        </avrgcccpp.assembler.general.IncludePaths>
-        <avrgcccpp.assembler.debugging.DebugLevel>Default (-Wa,-g)</avrgcccpp.assembler.debugging.DebugLevel>
-      </AvrGccCpp>
-    </ToolchainSettings>
-  </PropertyGroup>
-  <ItemGroup>
-    <Compile Include="clock.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="command.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="flash\flash.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="io\io.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="main.cpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="type\type.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\config.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\hardware.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\hardware0.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\hardware1.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\software.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\uart.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-  </ItemGroup>
-  <ItemGroup>
-    <Folder Include="flash" />
-    <Folder Include="io" />
-    <Folder Include="uart" />
-    <Folder Include="type" />
-  </ItemGroup>
-  <Import Project="$(AVRSTUDIO_EXE_PATH)\\Vs\\Compiler.targets" />
-</Project>

stk500v2/stk500v2.hpp

@@ -1,344 +0,0 @@
-#pragma once
-
-#include <math.h>
-#include <stddef.h>
-#include <stdint.h>
-
-namespace stk500v2 {
-
-enum class Msg : uint8_t {
-	START = 0x1B, // ASCII ESC
-	TOKEN = 0x0E,
-};
-
-inline constexpr bool operator==(const Msg &msg, const uint8_t &num)
-{
-	return static_cast<uint8_t>(msg) == num;
-}
-
-enum class Cmd : uint8_t {
-	SIGN_ON = 0x01,
-	SET_PARAMETER = 0x02,
-	GET_PARAMETER = 0x03,
-	SET_DEVICE_PARAMETERS = 0x04,
-	OSCCAL = 0x05,
-	LOAD_ADDRESS = 0x06,
-	FIRMWARE_UPGRADE = 0x07,
-};
-
-inline constexpr bool operator==(const Cmd &cmd, const uint8_t &num)
-{
-	return static_cast<uint8_t>(cmd) == num;
-}
-
-enum class IspCmd : uint8_t {
-	ENTER_PROGMODE = 0x10,
-	LEAVE_PROGMODE = 0x11,
-	CHIP_ERASE = 0x12,
-	PROGRAM_FLASH = 0x13,
-	READ_FLASH = 0x14,
-	PROGRAM_EEPROM = 0x15,
-	READ_EEPROM = 0x16,
-	PROGRAM_FUSE = 0x17,
-	READ_FUSE = 0x18,
-	PROGRAM_LOCK = 0x19,
-	READ_LOCK = 0x1A,
-	READ_SIGNATURE = 0x1B,
-	READ_OSCCAL = 0x1C,
-
-	SPI_MULTI = 0x1D,
-};
-
-enum class PpCmd : uint8_t {
-	ENTER_PROGMODE = 0x20,
-	LEAVE_PROGMODE = 0x21,
-	CHIP_ERASE = 0x22,
-	PROGRAM_FLASH = 0x23,
-	READ_FLASH = 0x24,
-	PROGRAM_EEPROM = 0x25,
-	READ_EEPROM = 0x26,
-	PROGRAM_FUSE = 0x27,
-	READ_FUSE = 0x28,
-	PROGRAM_LOCK = 0x29,
-	READ_LOCK = 0x2A,
-	READ_SIGNATURE = 0x2B,
-	READ_OSCCAL = 0x2C,
-
-	SET_CONTROL_STACK = 0x2D,
-};
-
-enum class HvspCmd : uint8_t {
-	ENTER_PROGMODE = 0x30,
-	LEAVE_PROGMODE = 0x31,
-	CHIP_ERASE = 0x32,
-	PROGRAM_FLASH = 0x33,
-	READ_FLASH = 0x34,
-	PROGRAM_EEPROM = 0x35,
-	READ_EEPROM = 0x36,
-	PROGRAM_FUSE = 0x37,
-	READ_FUSE = 0x38,
-	PROGRAM_LOCK = 0x39,
-	READ_LOCK = 0x3A,
-	READ_SIGNATURE = 0x3B,
-	READ_OSCCAL = 0x3C,
-};
-
-enum class Status : uint8_t {
-	// Success
-	CMD_OK = 0x00,
-
-	// Warnings
-	CMD_TOUT = 0x80,
-	RDY_BSY_TOUT = 0x81,
-	SET_PARAM_MISSING = 0x82,
-
-	// Errors
-	CMD_FAILED = 0xC0,
-	CKSUM_ERROR = 0xC1,
-	CMD_UNKNOWN = 0xC9,
-};
-
-enum class Param : uint8_t {
-	BUILD_NUMBER_LOW = 0x80,
-	BUILD_NUMBER_HIGH = 0x81,
-	HW_VER = 0x90,
-	SW_MAJOR = 0x91,
-	SW_MINOR = 0x92,
-	VTARGET = 0x94,
-	VADJUST = 0x95,
-	OSC_PSCALE = 0x96,
-	OSC_CMATCH = 0x97,
-	SCK_DURATION = 0x98,
-	TOPCARD_DETECT = 0x9A,
-	STATUS = 0x9C,
-	DATA = 0x9D,
-	RESET_POLARITY = 0x9E,
-	CONTROLLER_INIT = 0x9F,
-};
-
-enum class Answer : uint8_t {
-	CKSUM_ERROR = 0xB0,
-};
-
-template <size_t Size>
-struct Message {
-	uint8_t start;
-	uint8_t number;
-	uint16_t size;
-	uint8_t token;
-	uint8_t body[Size];
-	uint8_t checksum;
-};
-
-template <auto SignOnFn, auto SetParamFn, auto GetParamFn>
-struct Callbacks {
-	static constexpr auto onSignOn = SignOnFn;
-	static constexpr auto onSetParam = SetParamFn;
-	static constexpr auto onGetParam = GetParamFn;
-};
-
-template <class Uart, uint16_t Timeout, auto CallbackFns>
-class Stk500v2 {
-  public:
-	inline void init()
-	{
-		m_serial.init();
-	}
-
-	inline bool callback()
-	{
-		if (receiveMessage()) {
-			handleMessage();
-		}
-
-		if (m_timeout)
-			return true;
-
-		return false;
-	}
-
-  private:
-	static constexpr auto MSG_BUFFER_SIZE = 275;
-	using msg_t = Message<MSG_BUFFER_SIZE>;
-
-	msg_t m_msg;
-	Uart m_serial;
-	uint16_t m_timeout = Timeout;
-
-	inline bool receiveByte(uint8_t &data)
-	{
-		constexpr auto MICROSECOND = 1000.0 * 1000;
-		constexpr auto SYMBOL_SIZE = 9;
-		constexpr auto BYTE_DELAY_US = (SYMBOL_SIZE * MICROSECOND) / Uart::BAUD_RATE;
-		constexpr auto NUM_MS_DELAY_STEPS = static_cast<uint16_t>(round(1000 / BYTE_DELAY_US));
-		uint16_t msDelay = NUM_MS_DELAY_STEPS;
-
-		while (m_timeout) {
-			if (m_serial.rxByte(data)) {
-				m_timeout = Timeout;
-				return true;
-			}
-
-			_delay_us(BYTE_DELAY_US);
-
-			if (--msDelay == 0) {
-				msDelay = NUM_MS_DELAY_STEPS;
-				--m_timeout;
-			}
-		}
-
-		return false;
-	}
-
-	inline uint8_t calcChecksum() const
-	{
-		uint8_t checksum = static_cast<uint8_t>(m_msg.start);
-
-		for (uint16_t i = 1; i < 5 + m_msg.size; ++i) {
-			checksum ^= *(reinterpret_cast<const uint8_t *>(&m_msg) + i);
-		}
-
-		return checksum;
-	}
-
-	inline bool receiveMessage()
-	{
-		constexpr auto CHECK_MESSAGE_FORMAT = true;
-		constexpr auto CHECK_MESSAGE_SIZE = true;
-		constexpr auto CHECK_MESSAGE_CHECKSUM = true;
-
-		if (!receiveByte(m_msg.start)) {
-			return false;
-		}
-		if constexpr (CHECK_MESSAGE_FORMAT) {
-			if (m_msg.start != Msg::START)
-				return false;
-		}
-
-		if (!receiveByte(m_msg.number))
-			return false;
-
-		if (!receiveByte(*(reinterpret_cast<uint8_t *>(&m_msg.size) + 1)))
-			return false;
-		if (!receiveByte(*reinterpret_cast<uint8_t *>(&m_msg.size)))
-			return false;
-
-		if constexpr (CHECK_MESSAGE_SIZE) {
-			if (m_msg.size > sizeof(m_msg.body))
-				return false;
-		}
-
-		if (!receiveByte(m_msg.token))
-			return false;
-
-		if constexpr (CHECK_MESSAGE_FORMAT) {
-			if (m_msg.token != Msg::TOKEN)
-				return false;
-		}
-
-		for (uint16_t i = 0; i < m_msg.size; ++i) {
-			if (!receiveByte(m_msg.body[i]))
-				return false;
-		}
-
-		if (!receiveByte(m_msg.checksum))
-			return false;
-
-		if constexpr (CHECK_MESSAGE_CHECKSUM) {
-			if (m_msg.checksum != calcChecksum())
-				return false;
-		}
-
-		return true;
-	}
-
-	inline void transmitMessage() const
-	{
-		m_serial.txByte(m_msg.start);
-		m_serial.txByte(m_msg.number);
-		m_serial.txByte(m_msg.size >> 8);
-		m_serial.txByte(m_msg.size & 0xFF);
-		m_serial.txByte(m_msg.token);
-		for (uint16_t i = 0; i < m_msg.size; ++i)
-			m_serial.txByte(m_msg.body[i]);
-		m_serial.txByte(m_msg.checksum);
-	}
-
-	inline void handleMessage()
-	{
-		constexpr auto CHECK_MESSAGE_LENGTH = true;
-
-		switch (m_msg.body[0]) {
-		case static_cast<uint8_t>(Cmd::SIGN_ON): {
-			if constexpr (CHECK_MESSAGE_LENGTH) {
-				if (m_msg.size != 1)
-					break;
-			}
-			CallbackFns.onSignOn();
-			sendReply<static_cast<uint8_t>(Cmd::SIGN_ON)>();
-			break;
-		}
-		case static_cast<uint8_t>(Cmd::SET_PARAMETER): {
-			if constexpr (CHECK_MESSAGE_LENGTH) {
-				if (m_msg.size != 3)
-					break;
-			}
-			CallbackFns.onSetParam();
-			sendReply<static_cast<uint8_t>(Cmd::SET_PARAMETER)>();
-			break;
-		}
-		case static_cast<uint8_t>(Cmd::GET_PARAMETER): {
-			if constexpr (CHECK_MESSAGE_LENGTH) {
-				if (m_msg.size != 2)
-					break;
-			}
-			const auto errorOccurred = CallbackFns.onGetParam(static_cast<Param>(m_msg.body[1]), m_msg.body[2]);
-			sendReply<static_cast<uint8_t>(Cmd::GET_PARAMETER)>(errorOccurred);
-			break;
-		}
-		case static_cast<uint8_t>(Cmd::SET_DEVICE_PARAMETERS):
-			break;
-		case static_cast<uint8_t>(Cmd::OSCCAL):
-			break;
-		case static_cast<uint8_t>(Cmd::LOAD_ADDRESS):
-			break;
-		case static_cast<uint8_t>(Cmd::FIRMWARE_UPGRADE):
-			break;
-		}
-	}
-
-	template <uint8_t Command>
-	inline void sendReply(bool errorOccurred = false)
-	{
-		if constexpr (Command == Cmd::SIGN_ON) {
-			m_msg.size = 3 + 8;
-			m_msg.body[1] = static_cast<uint8_t>(Status::CMD_OK);
-			m_msg.body[2] = 8;
-			m_msg.body[3] = 'S';
-			m_msg.body[4] = 'T';
-			m_msg.body[5] = 'K';
-			m_msg.body[6] = '5';
-			m_msg.body[7] = '0';
-			m_msg.body[8] = '0';
-			m_msg.body[9] = '_';
-			m_msg.body[10] = '2';
-		} else if (Command == Cmd::SET_PARAMETER) {
-			m_msg.size = 2;
-			m_msg.body[1] = static_cast<uint8_t>(Status::CMD_OK);
-		} else if (Command == Cmd::GET_PARAMETER) {
-			if (!errorOccurred) {
-				m_msg.size = 3;
-				m_msg.body[1] = static_cast<uint8_t>(Status::CMD_OK);
-			} else {
-				m_msg.size = 2;
-				m_msg.body[1] = static_cast<uint8_t>(Status::CMD_FAILED);
-			}
-		}
-
-		m_msg.checksum = calcChecksum();
-
-		transmitMessage();
-	}
-};
-
-} // namespace stk500v2

test/check_size.cmake

@@ -0,0 +1,11 @@
+execute_process(COMMAND ${SIZE_TOOL} ${ELF} OUTPUT_VARIABLE _out RESULT_VARIABLE _res)
+if(NOT _res EQUAL 0)
+	message(FATAL_ERROR "avr-size failed")
+endif()
+# avr-size line 2 is "<text> <data> <bss> <dec> <hex> <file>".
+string(REGEX MATCH "\n[ \t]*([0-9]+)" _m "${_out}")
+set(_text ${CMAKE_MATCH_1})
+if(_text GREATER LIMIT)
+	message(FATAL_ERROR ".text is ${_text} bytes, over the ${LIMIT}-byte boot section")
+endif()
+message(STATUS ".text ${_text} <= ${LIMIT} (boot section budget)")

test/device.c

@@ -0,0 +1,109 @@
+// simavr "device" for the TSB bootloader: load the boot-linked ELF into the
+// ATmega328P boot section, enter it (BOOTRST is not modelled, so we set PC to
+// the boot base, exactly as simavr's own board_simduino does), and expose
+// UART0 as a pty. A host client (Python pyserial, or the real tsbloader) then
+// speaks the TSB protocol over that pty and actually flashes the device.
+//
+// SPM genuinely writes avr->flash on the mega cores, so on exit (or SIGTERM)
+// we dump the flash image to a file for a ground-truth cross-check against
+// what the client read back through the bootloader.
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "avr_uart.h"
+#include "sim_avr.h"
+#include "sim_elf.h"
+#include "uart_pty.h"
+
+static avr_t *avr;
+static uart_pty_t uart_pty;
+static const char *dump_path;
+
+static void finish(int sig)
+{
+	(void)sig;
+	if (dump_path) {
+		FILE *f = fopen(dump_path, "wb");
+		if (f) {
+			fwrite(avr->flash, 1, avr->flashend + 1, f);
+			fclose(f);
+		}
+	}
+	uart_pty_stop(&uart_pty);
+	_exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+	if (argc < 3) {
+		fprintf(stderr, "usage: %s <tsb.elf> <boot_base_hex> [flash_dump.bin]\n", argv[0]);
+		return 2;
+	}
+	uint32_t boot_base = (uint32_t)strtoul(argv[2], NULL, 0);
+	dump_path = argc >= 4 ? argv[3] : NULL;
+
+	avr = avr_make_mcu_by_name("atmega328p");
+	if (!avr) {
+		fprintf(stderr, "device: no ATmega328P core\n");
+		return 1;
+	}
+	avr_init(avr);
+	avr->frequency = 16000000;
+	// Real flash powers up erased (0xff); the app region must look erased
+	// before the bootloader programs it.
+	memset(avr->flash, 0xff, avr->flashend + 1);
+
+	// simavr's ELF loader flattens the flash base to 0 (it expects an app at
+	// 0x0), but it hands back the boot code in fw.flash; place it at the boot
+	// section base ourselves and enter there (BOOTRST is not modelled).
+	elf_firmware_t fw = {0};
+	if (elf_read_firmware(argv[1], &fw) != 0) {
+		fprintf(stderr, "device: cannot read %s\n", argv[1]);
+		return 1;
+	}
+	memcpy(avr->flash + boot_base, fw.flash, fw.flashsize);
+	avr->pc = boot_base;
+	avr->codeend = avr->flashend;
+
+	// Optional: seed the config page (one page below the boot section) with a
+	// hex byte string, so the password gate and emergency erase can be tested.
+	// Layout: [appjump lo][appjump hi][timeout][password...][0xff].
+	const char *cfg = getenv("TSB_CONFIG");
+	if (cfg) {
+		uint32_t app_end = boot_base - 128; // config page sits directly below the boot code
+		for (int i = 0; cfg[i] && cfg[i + 1]; i += 2) {
+			char b[3] = {cfg[i], cfg[i + 1], 0};
+			avr->flash[app_end + i / 2] = (uint8_t)strtoul(b, NULL, 16);
+		}
+	}
+
+	// POLL_SLEEP makes simavr usleep(1) on every status-register read while the
+	// UART is idle — a host-CPU-saving hack that models no hardware and paces a
+	// tight-polling loader (one that releases TX between bytes, as one-wire does)
+	// in real time, distorting protocol timing. Clear it so the loader runs at
+	// true cycle speed.
+	uint32_t uflags = 0;
+	avr_ioctl(avr, AVR_IOCTL_UART_GET_FLAGS('0'), &uflags);
+	uflags &= ~AVR_UART_FLAG_POLL_SLEEP;
+	avr_ioctl(avr, AVR_IOCTL_UART_SET_FLAGS('0'), &uflags);
+
+	uart_pty_init(avr, &uart_pty);
+	uart_pty_connect(&uart_pty, '0');
+	printf("TSB_PTY %s\n", uart_pty.pty.slavename);
+	fflush(stdout);
+
+	signal(SIGTERM, finish);
+	signal(SIGINT, finish);
+
+	for (;;) {
+		int state = avr_run(avr);
+		if (state == cpu_Done || state == cpu_Crashed)
+			break;
+	}
+	finish(0);
+	return 0;
+}

test/pbapp.cpp

@@ -0,0 +1,51 @@
+// Test-fixture application for the pureboot protocol test: prints "APP" on
+// the chip's serial link (the same link the loader uses) and idles — the
+// proof that the loader's hand-over, and on the tinies the host's
+// reset-vector surgery, actually launched it. Linked normally (crt, vectors
+// at 0); on the tinies its reset vector is the rjmp the host re-homes.
+#include <libavr/libavr.hpp>
+
+using namespace avr::literals;
+
+namespace {
+
+consteval avr::hertz_t clock()
+{
+	if (avr::hw::db.name == "ATtiny13A")
+		return 9.6_MHz;
+	if (avr::hw::db.name == "ATtiny85")
+		return 8_MHz;
+	return 16_MHz;
+}
+
+using dev = avr::device<{.clock = clock()}>;
+
+template <avr::hertz_t C, bool Hardware = avr::hw::db.has_reg("UDR0")>
+struct link {
+	using tx_t = avr::uart::usart0<C, {.baud = 115200_Bd, .max_baud_error = 2.5_pct}>;
+	static void tx(char c)
+	{
+		tx_t::write(static_cast<std::uint8_t>(c));
+	}
+};
+
+template <avr::hertz_t C>
+struct link<C, false> {
+	using tx_t = avr::uart::software_tx<C, avr::pb1, 57600_Bd>;
+	static void tx(char c)
+	{
+		tx_t::write(static_cast<std::uint8_t>(c));
+	}
+};
+
+} // namespace
+
+int main()
+{
+	avr::init<typename link<dev::clock>::tx_t>();
+	link<dev::clock>::tx('A');
+	link<dev::clock>::tx('P');
+	link<dev::clock>::tx('P');
+	while (true) {
+	}
+}

test/pbtest.py

@@ -0,0 +1,178 @@
+#!/usr/bin/env python3
+"""End-to-end pureboot protocol test: spawn the simavr device, then drive it
+with the real host tool (pureboot.py, as a subprocess over the device's pty)
+through flash + EEPROM + timeout + fuse + hand-over scenarios, and cross-check
+the tool's view against the simulator's ground-truth memory dumps.
+
+Usage: pbtest.py <device_bin> <pureboot_elf> <mcu> <hz> <base_hex> <page>
+                 <baud> <eeprom_size> <app_bin> <tool_py> <workdir>
+Exits 0 if every scenario passes.
+"""
+
+import os
+import signal
+import subprocess
+import sys
+import time
+
+
+def fail(message):
+    print(f"FAIL: {message}")
+    sys.exit(1)
+
+
+def rjmp_decode(word, at, flash_words):
+    """Where an rjmp word at word-address `at` lands — deliberately written
+    against the instruction-set definition (12-bit signed offset), not with
+    the host tool's encoder, so an encoding bug cannot verify itself."""
+    if word & 0xF000 != 0xC000:
+        fail(f"word at {at * 2:#06x} is {word:#06x}, not an rjmp")
+    offset = word & 0x0FFF
+    if offset >= 0x800:
+        offset -= 0x1000
+    return (at + 1 + offset) % flash_words
+
+
+class Device:
+    def __init__(self, binary, elf, mcu, hz, base, page, baud, dump):
+        self.proc = subprocess.Popen(
+            [binary, elf, mcu, hz, base, str(page), str(baud), dump],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+            text=True,
+        )
+        self.dump = dump
+        self.pty = None
+        deadline = time.time() + 5
+        while time.time() < deadline:
+            line = self.proc.stdout.readline()
+            if not line:
+                break
+            if line.startswith("PB_PTY"):
+                self.pty = line.split()[1]
+                break
+        if not self.pty:
+            self.stop()
+            raise RuntimeError("device did not report a pty")
+
+    def stop(self):
+        self.proc.terminate()
+        try:
+            self.proc.wait(timeout=3)
+        except subprocess.TimeoutExpired:
+            self.proc.kill()
+
+
+def run_tool(tool, pty, baud, *args):
+    result = subprocess.run(
+        [sys.executable, tool, "--port", pty, "--baud", str(baud), "--wait", "20", *args],
+        capture_output=True,
+        text=True,
+        timeout=120,
+    )
+    print(result.stdout, end="")
+    if result.returncode != 0:
+        fail(f"tool exited {result.returncode}: {result.stderr.strip()}")
+    return result.stdout
+
+
+def main():
+    (device_bin, elf, mcu, hz, base_hex, page, baud, eeprom_size, app_bin, tool, workdir) = sys.argv[1:]
+    base, page, baud, eeprom_size = int(base_hex, 0), int(page), int(baud), int(eeprom_size)
+    sys.path.insert(0, os.path.dirname(os.path.abspath(tool)))
+    import pureboot as pb
+
+    os.makedirs(workdir, exist_ok=True)
+    ee_image = bytes(range(0xA0, 0xB0))
+    ee_path = os.path.join(workdir, "ee.bin")
+    open(ee_path, "wb").write(ee_image)
+    dump = os.path.join(workdir, "flash_dump.bin")
+    read_flash = os.path.join(workdir, "readback_flash.bin")
+    read_eeprom = os.path.join(workdir, "readback_eeprom.bin")
+
+    # The geometry the host will discover, for computing the expected image.
+    info = pb.Info(
+        bytes([ord("P"), ord("B"), 1, 0, 0, 0, page])
+        + bytes([base & 0xFF, base >> 8, eeprom_size & 0xFF, eeprom_size >> 8])
+        + bytes([0 if mcu == "atmega328p" else 1])
+    )
+
+    device = Device(device_bin, elf, mcu, hz, base_hex, page, baud, dump)
+    try:
+        # Session 1: knock from reset, identify, program everything, stay.
+        out = run_tool(tool, device.pty, baud, "--info", "--fuses", "--flash", app_bin,
+                       "--eeprom", ee_path, "--timeout", "8", "--stay")
+        for needed in ("device: signature", "fuses:", "verify:", "activation timeout: 8 s", "stays"):
+            if needed not in out:
+                fail(f"session 1 output lacks {needed!r}")
+
+        # Session 2: reconnect into the live session, verify, dump, hand over
+        # is deferred — the pty must be reopened for the APP banner first.
+        out = run_tool(tool, device.pty, baud, "--verify-flash", app_bin, "--verify-eeprom", ee_path,
+                       "--read-flash", read_flash, "--read-eeprom", read_eeprom, "--stay")
+        if out.count("verify:") != 2:
+            fail("session 2 did not verify both memories")
+
+        eeprom_back = open(read_eeprom, "rb").read()
+        if eeprom_back[: len(ee_image)] != ee_image:
+            fail("EEPROM read-back mismatch")
+        if eeprom_back[-1] != 8:
+            fail(f"timeout cell reads {eeprom_back[-1]}, expected 8")
+
+        # The expected post-surgery flash, straight from the tool's planner.
+        pages = pb.plan_flash(open(app_bin, "rb").read(), info)
+        flash_back = open(read_flash, "rb").read()
+        for address, data in pages.items():
+            if flash_back[address : address + page] != data:
+                fail(f"flash read-back mismatch in page {address:#06x}")
+
+        # An external reset re-enters through the patched word 0 (tinies; the
+        # runner resets them to address 0 like silicon) or BOOTRST (mega).
+        # The loader must answer a fresh knock, and 'G' must land in the
+        # application, which banners on the same link.
+        device.proc.send_signal(signal.SIGUSR1)
+        port = pb.Port(device.pty, baud)
+        try:
+            loader = pb.Loader(port)
+            loader.connect(15)
+            port.write(b"G")
+            if port.read_exact(1, 5.0) != pb.PROMPT:
+                fail("no ack for G")
+            banner = port.read_exact(3, 5.0)
+            if banner != b"APP":
+                fail(f"application banner was {banner!r}")
+        finally:
+            port.close()
+    finally:
+        device.stop()
+
+    # Ground truth: the simulator's own memories, against the host's view.
+    flash_true = open(dump, "rb").read()
+    if flash_true[:base] != flash_back:
+        fail("host flash read-back differs from the simulator's flash")
+    if flash_true[base] == 0xFF and flash_true[base + 1] == 0xFF:
+        fail("loader region looks erased in the ground-truth dump")
+
+    # The surgery, decoded independently: the patched vector must land on the
+    # loader, the trampoline on the application's own entry.
+    if mcu != "atmega328p":
+        flash_words = (base + 512) // 2
+        app = open(app_bin, "rb").read()
+        word0 = flash_true[0] | (flash_true[1] << 8)
+        if rjmp_decode(word0, 0, flash_words) != base // 2:
+            fail("patched reset vector does not land on the loader base")
+        trampoline = flash_true[base - 2] | (flash_true[base - 1] << 8)
+        original = app[0] | (app[1] << 8)
+        if rjmp_decode(trampoline, (base - 2) // 2, flash_words) != rjmp_decode(original, 0, flash_words):
+            fail("trampoline does not land on the application's own entry")
+    ee_true_path = dump + ".eeprom"
+    if os.path.exists(ee_true_path):
+        ee_true = open(ee_true_path, "rb").read()
+        if ee_true[: len(ee_image)] != ee_image or ee_true[-1] != 8:
+            fail("ground-truth EEPROM does not match what was programmed")
+
+    print("pbtest: all scenarios pass")
+
+
+if __name__ == "__main__":
+    main()

test/pureboot_device.c

@@ -0,0 +1,323 @@
+// simavr "device" for the pureboot protocol tests, all three chips. Loads
+// the boot-linked ELF at the loader base, starts execution there (BOOTRST /
+// the patched vector are not what is under test), and exposes the loader's
+// serial link as a pty for the real host tool:
+//
+//   - ATmega328P: the hardware USART0 through simavr's uart_pty.
+//   - Tinies: an 8N1 bridge between a pty and the GPIO software UART
+//     (drives PB0, the loader's RX; decodes PB1, its TX), timed against the
+//     simulated cycle counter.
+//
+// simavr's tiny cores decode the SPM opcode but attach no NVM module — SPM
+// is a silent no-op (the mega's boot section has one, avr_flash). The
+// missing module is supplied here: the SPM ioctl reads SPMCSR/Z/r1:r0 and
+// implements buffer fill, page erase, page write, and CTPB, completing
+// instantly. RFLB's LPM diversion (fuse readout) stays unmodeled, so the
+// 'F' command answers with flash bytes — the tests assert transport only.
+//
+// On exit (or SIGTERM) the flash and EEPROM are dumped to files for a
+// ground-truth cross-check against what the host read back.
+#include <fcntl.h>
+#include <pty.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+
+#include "avr_eeprom.h"
+#include "avr_flash.h"
+#include "avr_ioport.h"
+#include "avr_uart.h"
+#include "sim_avr.h"
+#include "sim_elf.h"
+#include "sim_io.h"
+#include "uart_pty.h"
+
+static avr_t *avr;
+static uart_pty_t uart_pty;
+static int use_uart_pty;
+static const char *dump_path;
+static uint32_t reset_pc;
+static volatile sig_atomic_t reset_requested;
+
+static void request_reset(int sig)
+{
+	(void)sig;
+	reset_requested = 1;
+}
+
+// ------------------------------------------------------------- tiny NVM ---
+
+typedef struct {
+	avr_io_t io;
+	uint8_t buffer[128];
+	unsigned page;
+} tiny_nvm_t;
+
+static tiny_nvm_t nvm;
+
+static int nvm_ioctl(avr_io_t *io, uint32_t ctl, void *param)
+{
+	(void)param;
+	if (ctl != AVR_IOCTL_FLASH_SPM)
+		return -1;
+	tiny_nvm_t *n = (tiny_nvm_t *)io;
+	avr_t *mcu = io->avr;
+	uint8_t command = mcu->data[0x57] & 0x1f; // SPMCSR, both tinies
+	uint16_t z = (uint16_t)(mcu->data[30] | (mcu->data[31] << 8));
+	uint32_t page_base = (uint32_t)(z & ~(n->page - 1)) % (mcu->flashend + 1);
+	if (command == 0x01) { // SPMEN alone: buffer fill from r1:r0
+		unsigned offset = z & (n->page - 1) & ~1u;
+		n->buffer[offset] = mcu->data[0];
+		n->buffer[offset + 1] = mcu->data[1];
+	} else if (command == 0x03) { // PGERS
+		memset(mcu->flash + page_base, 0xff, n->page);
+	} else if (command == 0x05) { // PGWRT: programming only clears bits
+		for (unsigned i = 0; i < n->page; i++)
+			mcu->flash[page_base + i] &= n->buffer[i];
+		memset(n->buffer, 0xff, n->page);
+	} else if (command == 0x11) { // CTPB
+		memset(n->buffer, 0xff, n->page);
+	}
+	mcu->data[0x57] &= (uint8_t)~0x1f; // the operation completes instantly
+	return 0;
+}
+
+// ----------------------------------------------------------- GPIO bridge ---
+
+static int pty_master = -1;
+static avr_irq_t *rx_pin; // the loader's RX (PB0), driven from the pty
+static avr_cycle_count_t bit_cycles;
+
+static int tx_level = 1, tx_active, tx_bit;
+static uint8_t tx_shift;
+
+static avr_cycle_count_t tx_sample(avr_t *mcu, avr_cycle_count_t when, void *param)
+{
+	(void)mcu;
+	(void)param;
+	tx_shift = (uint8_t)((tx_shift >> 1) | (tx_level ? 0x80 : 0));
+	if (++tx_bit < 8)
+		return when + bit_cycles;
+	if (write(pty_master, &tx_shift, 1) != 1)
+		fprintf(stderr, "device: pty write lost a byte\n");
+	tx_active = 0;
+	return 0;
+}
+
+static void tx_hook(avr_irq_t *irq, uint32_t value, void *param)
+{
+	(void)irq;
+	(void)param;
+	int level = value & 1;
+	if (!tx_active && tx_level == 1 && level == 0) { // start edge
+		tx_active = 1;
+		tx_bit = 0;
+		avr_cycle_timer_register(avr, bit_cycles + bit_cycles / 2, tx_sample, NULL);
+	}
+	tx_level = level;
+}
+
+static uint8_t rx_queue[8192];
+static unsigned rx_head, rx_tail; // ring: head = next to send
+static int rx_active, rx_bit;
+static uint8_t rx_byte;
+
+static void rx_start_next(void);
+
+static avr_cycle_count_t rx_step(avr_t *mcu, avr_cycle_count_t when, void *param)
+{
+	(void)mcu;
+	(void)param;
+	if (rx_bit < 8) {
+		avr_raise_irq(rx_pin, (rx_byte >> rx_bit) & 1);
+		rx_bit++;
+		return when + bit_cycles;
+	}
+	if (rx_bit == 8) { // stop bit, plus one idle bit of margin
+		avr_raise_irq(rx_pin, 1);
+		rx_bit++;
+		return when + 2 * bit_cycles;
+	}
+	rx_active = 0;
+	rx_start_next();
+	return 0;
+}
+
+static void rx_start_next(void)
+{
+	if (rx_active || rx_head == rx_tail)
+		return;
+	rx_byte = rx_queue[rx_head];
+	rx_head = (rx_head + 1) % sizeof(rx_queue);
+	rx_active = 1;
+	rx_bit = 0;
+	avr_raise_irq(rx_pin, 0); // start bit
+	avr_cycle_timer_register(avr, bit_cycles, rx_step, NULL);
+}
+
+// A reset abandons whatever the bridge was mid-transfer: bytes still queued
+// for a chip that no longer has the context to receive them meaningfully,
+// and a decode in progress on a TX line the reset may have already changed.
+static void bridge_reset(void)
+{
+	rx_head = rx_tail = 0;
+	rx_active = 0;
+	tx_active = 0;
+	tx_level = 1;
+	avr_raise_irq(rx_pin, 1); // idle line
+}
+
+static void poll_pty(void)
+{
+	uint8_t chunk[256];
+	ssize_t got = read(pty_master, chunk, sizeof(chunk));
+	for (ssize_t i = 0; i < got; i++) {
+		unsigned next = (rx_tail + 1) % sizeof(rx_queue);
+		if (next == rx_head)
+			break; // full: the host will retry on timeout
+		rx_queue[rx_tail] = chunk[i];
+		rx_tail = next;
+	}
+	if (got > 0)
+		rx_start_next();
+}
+
+// ------------------------------------------------------------------ main ---
+
+static void finish(int sig)
+{
+	(void)sig;
+	if (dump_path) {
+		FILE *f = fopen(dump_path, "wb");
+		if (f) {
+			fwrite(avr->flash, 1, avr->flashend + 1, f);
+			fclose(f);
+		}
+		avr_eeprom_desc_t ee = {.ee = NULL, .offset = 0, .size = 0};
+		if (avr_ioctl(avr, AVR_IOCTL_EEPROM_GET, &ee) == 0 && ee.ee && ee.size) {
+			char path[512];
+			snprintf(path, sizeof(path), "%s.eeprom", dump_path);
+			f = fopen(path, "wb");
+			if (f) {
+				fwrite(ee.ee, 1, ee.size, f);
+				fclose(f);
+			}
+		}
+	}
+	if (use_uart_pty)
+		uart_pty_stop(&uart_pty);
+	_exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+	if (argc != 8) {
+		fprintf(stderr, "usage: %s <pureboot.elf> <mcu> <hz> <base_hex> <page> <baud> <flash_dump>\n", argv[0]);
+		return 2;
+	}
+	const char *mcu_name = argv[2];
+	uint32_t base = (uint32_t)strtoul(argv[4], NULL, 0);
+	unsigned page = (unsigned)atoi(argv[5]);
+	unsigned baud = (unsigned)atoi(argv[6]);
+	dump_path = argv[7];
+	use_uart_pty = strcmp(mcu_name, "atmega328p") == 0;
+
+	avr = avr_make_mcu_by_name(mcu_name);
+	if (!avr) {
+		fprintf(stderr, "device: no %s core\n", mcu_name);
+		return 1;
+	}
+	avr_init(avr);
+	avr->frequency = (uint32_t)strtoul(argv[3], NULL, 0);
+	memset(avr->flash, 0xff, avr->flashend + 1); // real flash powers up erased
+
+	elf_firmware_t fw = {0};
+	if (elf_read_firmware(argv[1], &fw) != 0) {
+		fprintf(stderr, "device: cannot read %s\n", argv[1]);
+		return 1;
+	}
+	memcpy(avr->flash + base, fw.flash, fw.flashsize);
+	// The mega enters the loader in hardware (BOOTRST, not modeled); the
+	// tinies reset to word 0 like silicon — erased flash walks up into the
+	// loader, and after the host's surgery the patched vector routes there.
+	reset_pc = use_uart_pty ? base : 0;
+	avr->pc = reset_pc;
+	avr->codeend = avr->flashend;
+
+	// Erased EEPROM, as hardware powers up (simavr zeroes it).
+	uint8_t blank[1024];
+	memset(blank, 0xff, sizeof(blank));
+	avr_eeprom_desc_t seed = {.ee = blank, .offset = 0, .size = 0};
+	if (avr_ioctl(avr, AVR_IOCTL_EEPROM_GET, &seed) == 0 && seed.size <= sizeof(blank)) {
+		seed.ee = blank;
+		avr_ioctl(avr, AVR_IOCTL_EEPROM_SET, &seed);
+	}
+
+	if (use_uart_pty) {
+		// POLL_SLEEP paces an idle-polling loader in host real time (a
+		// no-hardware CPU-saving hack); clear it so cycles run free.
+		uint32_t flags = 0;
+		avr_ioctl(avr, AVR_IOCTL_UART_GET_FLAGS('0'), &flags);
+		flags &= ~AVR_UART_FLAG_POLL_SLEEP;
+		avr_ioctl(avr, AVR_IOCTL_UART_SET_FLAGS('0'), &flags);
+		uart_pty_init(avr, &uart_pty);
+		uart_pty_connect(&uart_pty, '0');
+		printf("PB_PTY %s\n", uart_pty.pty.slavename);
+	} else {
+		nvm.page = page;
+		memset(nvm.buffer, 0xff, sizeof(nvm.buffer));
+		nvm.io.kind = "tiny_nvm";
+		nvm.io.ioctl = nvm_ioctl;
+		avr_register_io(avr, &nvm.io);
+
+		bit_cycles = (avr->frequency + baud / 2) / baud; // matches uart.hpp's own rounding exactly
+		rx_pin = avr_io_getirq(avr, AVR_IOCTL_IOPORT_GETIRQ('B'), 0);
+		avr_irq_register_notify(avr_io_getirq(avr, AVR_IOCTL_IOPORT_GETIRQ('B'), 1), tx_hook, NULL);
+		avr_raise_irq(rx_pin, 1); // idle line
+
+		int slave;
+		struct termios raw;
+		cfmakeraw(&raw);
+		if (openpty(&pty_master, &slave, NULL, &raw, NULL) != 0) {
+			fprintf(stderr, "device: openpty failed\n");
+			return 1;
+		}
+		fcntl(pty_master, F_SETFL, O_NONBLOCK);
+		printf("PB_PTY %s\n", ttyname(slave));
+	}
+	fflush(stdout);
+
+	signal(SIGTERM, finish);
+	signal(SIGINT, finish);
+	signal(SIGUSR1, request_reset); // an external reset line, for the tests
+
+	long since_poll = 0;
+	for (;;) {
+		int state = avr_run(avr);
+		if (state == cpu_Done || state == cpu_Crashed)
+			break;
+		if (reset_requested) {
+			reset_requested = 0;
+			avr_reset(avr);
+			avr->pc = reset_pc;
+			if (use_uart_pty) { // reset restores the pacing hack; re-clear it
+				uint32_t flags = 0;
+				avr_ioctl(avr, AVR_IOCTL_UART_GET_FLAGS('0'), &flags);
+				flags &= ~AVR_UART_FLAG_POLL_SLEEP;
+				avr_ioctl(avr, AVR_IOCTL_UART_SET_FLAGS('0'), &flags);
+			} else {
+				bridge_reset();
+			}
+		}
+		if (!use_uart_pty && ++since_poll >= 2000) {
+			since_poll = 0;
+			poll_pty();
+		}
+	}
+	finish(0);
+	return 0;
+}

test/tsbtest.py

@@ -0,0 +1,252 @@
+#!/usr/bin/env python3
+"""End-to-end TSB protocol test: spawn the simavr device, speak the TinySafeBoot
+wire protocol over its pty (as the real host tools do), and actually flash it.
+
+Usage: tsbtest.py <device_binary> <tsb.elf> <boot_base_hex>
+Exits 0 if every scenario passes.
+"""
+import os
+import subprocess
+import sys
+import time
+
+import serial
+
+CONFIRM = 0x21  # '!'
+REQUEST = 0x3F  # '?'
+KNOCK = 0x40    # '@'
+PAGE = 128      # ATmega328P: 64 words
+
+
+class Device:
+    """The simavr runner, exposing UART0 as a pty. `config` seeds the config
+    page (via the device's TSB_CONFIG hook) so the password gate and emergency
+    erase are exercisable."""
+
+    def __init__(self, binary, elf, boot_base, dump="/tmp/tsb_dump.bin", config=None):
+        env = dict(os.environ)
+        if config is not None:
+            env["TSB_CONFIG"] = config
+        self.proc = subprocess.Popen(
+            [binary, elf, boot_base, dump],
+            stdout=subprocess.PIPE, stderr=subprocess.STDOUT, text=True, env=env)
+        self.dump = dump
+        self.pty = None
+        deadline = time.time() + 5
+        while time.time() < deadline:
+            line = self.proc.stdout.readline()
+            if not line:
+                break
+            if line.startswith("TSB_PTY"):
+                self.pty = line.split()[1]
+                break
+        if not self.pty:
+            self.stop()
+            raise RuntimeError("device did not report a pty")
+
+    def stop(self):
+        self.proc.terminate()
+        try:
+            self.proc.wait(timeout=3)
+        except subprocess.TimeoutExpired:
+            self.proc.kill()
+
+
+class Host:
+    """A faithful TSB host, per the wire protocol."""
+
+    def __init__(self, pty):
+        self.s = serial.Serial(pty, 115200, timeout=1.5)
+        self.info = None
+
+    def _read(self, n):
+        data = self.s.read(n)
+        if len(data) != n:
+            raise AssertionError(f"expected {n} bytes, got {len(data)}: {data.hex()}")
+        return data
+
+    def activate(self):
+        self.s.reset_input_buffer()
+        self.s.write(b"@@@")
+        reply = self._read(17)
+        if reply[16] != CONFIRM:
+            raise AssertionError(f"activation reply not '!'-terminated: {reply.hex()}")
+        self.info = reply[:16]
+        return self.info
+
+    # Parsed info-block fields (host math from the spec).
+    @property
+    def pagesize(self):
+        return self.info[9] * 2
+
+    @property
+    def appflash(self):
+        return (self.info[10] | (self.info[11] << 8)) * 2
+
+    @property
+    def eeprom_size(self):
+        return (self.info[12] | (self.info[13] << 8)) + 1
+
+    def _expect(self, byte, what):
+        r = self._read(1)
+        if r[0] != byte:
+            raise AssertionError(f"{what}: expected {byte:#x}, got {r.hex()}")
+
+    # Host-paced page read ('f'/'e'): send '!', take a page, repeat; stop with
+    # anything else, then the Mainloop '!'.
+    def _read_pages(self, cmd, npages):
+        self.s.write(cmd.encode())
+        data = b""
+        for _ in range(npages):
+            self.s.write(bytes([CONFIRM]))
+            data += self._read(PAGE)
+        self.s.write(bytes([REQUEST]))  # stop
+        self._expect(CONFIRM, f"{cmd} end")
+        return data
+
+    # Device-paced page write ('F'/'E'): device offers '?', host sends '!'+page,
+    # or anything else to stop.
+    def _write_pages(self, cmd, data):
+        if len(data) % PAGE:
+            data += b"\xff" * (PAGE - len(data) % PAGE)
+        self.s.write(cmd.encode())
+        for off in range(0, len(data), PAGE):
+            self._expect(REQUEST, f"{cmd} '?'")
+            self.s.write(bytes([CONFIRM]) + data[off:off + PAGE])
+        self._expect(REQUEST, f"{cmd} trailing '?'")
+        self.s.write(bytes([REQUEST]))  # stop
+        self._expect(CONFIRM, f"{cmd} end")
+
+    def write_flash(self, data):
+        self._write_pages("F", data)
+
+    def read_flash(self, npages):
+        return self._read_pages("f", npages)
+
+    def write_eeprom(self, data):
+        self._write_pages("E", data)
+
+    def read_eeprom(self, npages):
+        return self._read_pages("e", npages)
+
+    def read_config(self):
+        self.s.write(b"c")
+        page = self._read(PAGE)
+        self._expect(CONFIRM, "c end")
+        return page
+
+    def write_config(self, data):
+        assert len(data) == PAGE
+        self.s.write(b"C")
+        self._expect(REQUEST, "C '?'")
+        self.s.write(bytes([CONFIRM]) + data)
+        echo = self._read(PAGE)  # device echoes what it programmed
+        self._expect(CONFIRM, "C end")
+        return echo
+
+    # Activation when the config page carries a password: 3×'@' then the
+    # password bytes, then the info block + mainloop '!'.
+    def activate_password(self, password):
+        self.s.reset_input_buffer()
+        self.s.write(bytes([KNOCK, KNOCK, KNOCK]) + password)
+        reply = self._read(17)
+        if reply[16] != CONFIRM:
+            raise AssertionError(f"password activation not '!'-terminated: {reply.hex()}")
+        self.info = reply[:16]
+        return self.info
+
+    # A 0 byte where a password byte is expected requests emergency erase; the
+    # device asks for two confirmations, then wipes and returns to the mainloop.
+    def emergency_erase(self):
+        self.s.reset_input_buffer()
+        self.s.write(bytes([KNOCK, KNOCK, KNOCK, 0x00]))
+        self._expect(REQUEST, "emergency confirm 1")
+        self.s.write(bytes([CONFIRM]))
+        self._expect(REQUEST, "emergency confirm 2")
+        self.s.write(bytes([CONFIRM]))
+        self._expect(CONFIRM, "emergency mainloop ready")
+
+
+def check(cond, msg):
+    if not cond:
+        raise AssertionError(msg)
+    print(f"  ok: {msg}")
+
+
+# A config page carrying a password "PW": appjump 0, timeout 0x40, password
+# 0x50 0x57 terminated by 0xff.
+PW_CONFIG = "0000405057ff"
+PW_BYTES = bytes([0x50, 0x57])
+
+
+def scenario_roundtrip(host):
+    """Activation + info block + flash/EEPROM/config read-write round-trips, on
+    a device with a blank (erased) config page — the usual no-password case."""
+    info = host.activate()
+    check(info[0:3] == b"TSB", f"magic 'TSB' (got {info[0:3]!r})")
+    check(info[6:9] == bytes([0x1E, 0x95, 0x0F]), f"signature 1E 95 0F (got {info[6:9].hex()})")
+    check(info[14] == info[15], f"device-type bytes 14==15 (got {info[14]:#x},{info[15]:#x})")
+    check(host.pagesize == PAGE, f"page size {PAGE} (got {host.pagesize})")
+    check(host.eeprom_size == 1024, f"eeprom size 1024 (got {host.eeprom_size})")
+    print(f"  info: {info.hex()}  appflash={host.appflash} eeprom={host.eeprom_size}")
+
+    app = bytes(range(256))  # two pages of known data
+    host.write_flash(app)
+    check(host.read_flash(2) == app, "flash round-trip 2 pages")
+
+    edata = bytes((i * 7) & 0xFF for i in range(PAGE))
+    host.write_eeprom(edata)
+    check(host.read_eeprom(1) == edata, "eeprom round-trip 1 page")
+
+    cfg = bytes([0x00, 0x00, 0x40]) + b"\xff" * (PAGE - 3)  # timeout 0x40, no password
+    check(host.write_config(cfg) == cfg, "config write echoes the programmed page")
+    check(host.read_config() == cfg, "config read-back matches")
+
+
+def scenario_password(host):
+    """A device whose config page carries a password activates only when the
+    host sends it after the knock."""
+    info = host.activate_password(PW_BYTES)
+    check(info[0:3] == b"TSB", f"password activation returns the info block (got {info[0:3]!r})")
+
+
+def scenario_emergency(host):
+    """Emergency erase (password 0-byte + two confirms) wipes flash, EEPROM and
+    the config page; the device stays alive in its boot section."""
+    host.emergency_erase()
+    check(host.read_config() == b"\xff" * PAGE, "config page wiped")
+    check(host.read_flash(1) == b"\xff" * PAGE, "application flash wiped")
+    check(host.read_eeprom(1) == b"\xff" * PAGE, "EEPROM wiped")
+
+
+def main():
+    binary, elf, boot_base = sys.argv[1], sys.argv[2], sys.argv[3]
+    failures = []
+
+    # Each group runs on its own freshly-reset device (simavr reloads the ELF,
+    # so nothing persists between them); the password groups seed a config page.
+    groups = [
+        ("round-trip", None, scenario_roundtrip),
+        ("password activation", PW_CONFIG, scenario_password),
+        ("emergency erase", PW_CONFIG, scenario_emergency),
+    ]
+    for name, config, fn in groups:
+        print(f"--- {name} ---")
+        dev = Device(binary, elf, boot_base, config=config)
+        try:
+            fn(Host(dev.pty))
+        except AssertionError as e:
+            failures.append(f"{name}: {e}")
+            print(f"  FAIL: {e}")
+        finally:
+            dev.stop()
+
+    if failures:
+        print(f"FAILED ({len(failures)})")
+        return 1
+    print("ALL PASS")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

tsb/clock.hpp

@@ -1,4 +0,0 @@
-#pragma once
-
-#define F_CPU 18'432'000
-#include <util/delay.h>

tsb/main.cpp

@@ -1,102 +0,0 @@
-#include "clock.hpp"
-
-#include "uart/uart.hpp"
-
-constexpr auto READ_FLASH_CMD = 'f';
-constexpr auto WRITE_FLASH_CMD = 'F';
-constexpr auto READ_EEPROM_CMD = 'e';
-constexpr auto WRITE_EEPROM_CMD = 'E';
-constexpr auto READ_USERDATA_CMD = 'c';
-constexpr auto WRITE_USERDATA_CMD = 'C';
-constexpr auto REQUEST_CMD = '?';
-constexpr auto CONFIRM_CMD = '!';
-constexpr auto AUTO_BAUDING_CMD = '@';
-
-using uart_interface = uart::Hardware0<uart::Config<115200>, uart::Driven::BLOCKING>;
-
-enum class State {
-	WAITING,
-	ACTIVE,
-};
-
-struct DeviceInfo {
-	char name[3] = {'T', 'S', 'B'};
-	uint8_t date[2] = {0x1a, 0x1f};
-	uint8_t status = 0xf0;
-	uint8_t signature[3] = {0x1e, 0x95, 0x0f};
-	uint8_t pageSize = 0x40;
-	uint16_t flashSize = 0x3ec0;
-	uint16_t eepromSize = 0x03ff;
-};
-
-struct UserData {
-	uint16_t jumpAddress = 0xAAAA;
-	uint8_t timeout = 0x21;
-};
-
-static inline void sendDeviceInfo()
-{
-	uart::Uart<uart_interface> serial;
-
-	constexpr DeviceInfo deviceInfo;
-	constexpr UserData userData;
-
-	for (uint8_t i = 0; i < sizeof(deviceInfo); ++i) {
-		serial.txByte(*(reinterpret_cast<const uint8_t *>(&deviceInfo) + i));
-	}
-
-	for (uint8_t i = 0; i < sizeof(userData); ++i) {
-		serial.txByte(*(reinterpret_cast<const uint8_t *>(&userData) + i));
-	}
-}
-
-static uint8_t g_lastPage[128] = {};
-
-static inline void sendUserData()
-{
-	uart::Uart<uart_interface> serial;
-
-	for (uint8_t i = 0; i < sizeof(g_lastPage); ++i) {
-		serial.txByte(*(reinterpret_cast<const uint8_t *>(&g_lastPage) + i));
-	}
-}
-
-static inline void sendConfirm()
-{
-	uart::Uart<uart_interface> serial;
-	serial.txByte(CONFIRM_CMD);
-}
-
-int main()
-{
-	uart::Uart<uart_interface> serial;
-	serial.init();
-
-	State state = State::WAITING;
-
-	uint8_t receivedByte = 0;
-	uint8_t autoBaudingCounter = 0;
-
-	while (true) {
-		if (serial.rxByte(receivedByte)) {
-			if (state == State::WAITING) {
-				if (receivedByte == AUTO_BAUDING_CMD) {
-					++autoBaudingCounter;
-				}
-				if (autoBaudingCounter == 3) {
-					autoBaudingCounter = 0;
-					state = State::ACTIVE;
-					sendDeviceInfo();
-				}
-			} else if (state == State::ACTIVE) {
-				if (receivedByte == READ_USERDATA_CMD) {
-					sendUserData();
-					sendConfirm();
-					state = State::WAITING;
-				}
-			}
-		}
-	}
-
-	return 0;
-}

tsb/tsb.cppproj

@@ -1,263 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="14.0">
-  <PropertyGroup>
-    <SchemaVersion>2.0</SchemaVersion>
-    <ProjectVersion>7.0</ProjectVersion>
-    <ToolchainName>com.Atmel.AVRGCC8.CPP</ToolchainName>
-    <ProjectGuid>dce6c7e3-ee26-4d79-826b-08594b9ad897</ProjectGuid>
-    <avrdevice>ATmega328P</avrdevice>
-    <avrdeviceseries>none</avrdeviceseries>
-    <OutputType>Executable</OutputType>
-    <Language>CPP</Language>
-    <OutputFileName>$(MSBuildProjectName)</OutputFileName>
-    <OutputFileExtension>.elf</OutputFileExtension>
-    <OutputDirectory>$(MSBuildProjectDirectory)\$(Configuration)</OutputDirectory>
-    <AssemblyName>tsb</AssemblyName>
-    <Name>tsb</Name>
-    <RootNamespace>tsb</RootNamespace>
-    <ToolchainFlavour>avr-g++-9.1.0</ToolchainFlavour>
-    <KeepTimersRunning>true</KeepTimersRunning>
-    <OverrideVtor>false</OverrideVtor>
-    <CacheFlash>true</CacheFlash>
-    <ProgFlashFromRam>true</ProgFlashFromRam>
-    <RamSnippetAddress>0x20000000</RamSnippetAddress>
-    <UncachedRange />
-    <preserveEEPROM>true</preserveEEPROM>
-    <OverrideVtorValue>exception_table</OverrideVtorValue>
-    <BootSegment>2</BootSegment>
-    <ResetRule>0</ResetRule>
-    <eraseonlaunchrule>0</eraseonlaunchrule>
-    <EraseKey />
-    <avrtool>
-    </avrtool>
-    <avrtoolserialnumber>J41800099437</avrtoolserialnumber>
-    <avrdeviceexpectedsignature>0x1E9705</avrdeviceexpectedsignature>
-    <com_atmel_avrdbg_tool_stk500>
-      <ToolOptions>
-        <InterfaceProperties>
-          <IspClock>125000</IspClock>
-        </InterfaceProperties>
-        <InterfaceName>ISP</InterfaceName>
-      </ToolOptions>
-      <ToolType>com.atmel.avrdbg.tool.stk500</ToolType>
-      <ToolNumber>
-      </ToolNumber>
-      <ToolName>STK500</ToolName>
-    </com_atmel_avrdbg_tool_stk500>
-    <avrtoolinterface>ISP</avrtoolinterface>
-    <avrtoolinterfaceclock>125000</avrtoolinterfaceclock>
-    <AsfFrameworkConfig>
-      <framework-data xmlns="">
-        <options />
-        <configurations />
-        <files />
-        <documentation help="" />
-        <offline-documentation help="" />
-        <dependencies>
-          <content-extension eid="atmel.asf" uuidref="Atmel.ASF" version="3.47.0" />
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-    </AsfFrameworkConfig>
-    <com_atmel_avrdbg_tool_atmelice>
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-      <ToolName xmlns="">Simulator</ToolName>
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-    <AAFDebugger>
-      <AAFDebugFiles>
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-    </AAFDebugger>
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-  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
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-    </ToolchainSettings>
-  </PropertyGroup>
-  <ItemGroup>
-    <Compile Include="clock.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="flash\flash.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="io\io.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="main.cpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="type\type.hpp">
-      <SubType>compile</SubType>
-    </Compile>
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-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\hardware.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\hardware0.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\hardware1.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\software.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="uart\uart.hpp">
-      <SubType>compile</SubType>
-    </Compile>
-  </ItemGroup>
-  <ItemGroup>
-    <Folder Include="flash" />
-    <Folder Include="io" />
-    <Folder Include="uart" />
-    <Folder Include="type" />
-  </ItemGroup>
-  <Import Project="$(AVRSTUDIO_EXE_PATH)\\Vs\\Compiler.targets" />
-</Project>

tsb/tsb_asm.cpp

@@ -0,0 +1,386 @@
+// TinySafeBoot on libavr — tier 3: full feature parity in the 512-byte boot
+// section, in C++ except where the C ABI itself is the cost.
+//
+// The complete TinySafeBoot feature set — watchdog-reset bail, one-wire
+// half-duplex UART, a config-page activation timeout, the password gate,
+// emergency erase, and config/flash/EEPROM read-write — at 510 bytes in the
+// 512-byte BOOTSZ=11 section the hand-written oracle occupies (500 B). This tier used to be one
+// monolithic inline-asm routine; it is now the tricks tier's C++ (same
+// register protocol, same structure — see tsb_tricks.cpp, including the
+// global-register miscompile rules) with exactly two routines kept in
+// assembly, the two whose remaining cost *is* the calling convention:
+//
+//   rx     the bounded receive: C++ must re-floor the timeout window on every
+//          call (the global-register-store miscompile) and split it across
+//          call-saved registers; the asm keeps the oracle's X-register nested
+//          countdown.
+//   store  the page-store loop: C++ cannot hold the receive byte pair and the
+//          walked Z pointer across the rx calls without call-saved staging
+//          (push/pop + a Y→Z copy per word); the asm calls rx knowing exactly
+//          which registers it touches and walks Z live across the whole page.
+//
+// Everything else — bring-up, activation, password gate, emergency erase,
+// dispatch, every SPM/EEPROM/flash primitive, every geometry/baud/info
+// constant — is C++ on libavr, and the two asm routines splice into the same
+// global-register protocol the C++ uses (g_addr in Y, g_cnt in r16, g_window
+// in r7, g_receiving in r6), so calls cross the boundary with no marshalling.
+//
+// The wire protocol is strict request/response, which is what makes the shared
+// line safe: the device drives it only between a received command and its
+// reply, and releases it (RXEN0 only) whenever it waits.
+
+#include <libavr/libavr.hpp>
+
+#include <avr/io.h> // SP / RAMEND for the crt-free boot entry, SFR addresses for the asm routines
+
+using namespace avr::literals;
+namespace spm = avr::spm;
+namespace ee = avr::eeprom;
+namespace hw = avr::hw;
+
+namespace tsb {
+namespace {
+
+// The loader is purely polled — it never enables interrupts — so every SPM and
+// EEPROM lock folds to nothing under this posture.
+constexpr auto off = avr::irq::guard_policy::unused;
+
+constexpr std::uint8_t confirm = '!';
+constexpr std::uint8_t request = '?';
+constexpr std::uint8_t knock = '@';
+
+// Boot geometry for the 512 B boot section (BOOTSZ=11); the page size and the
+// flash/EEPROM extents are the chip database's to know. app_end is the config
+// page (TSB's LASTPAGE), one page below the boot section.
+constexpr std::uint16_t page = spm::page_bytes;
+constexpr std::uint16_t boot_bytes = 512;
+constexpr std::uint16_t app_end = spm::flash_bytes - boot_bytes - page;
+constexpr std::uint16_t eeprom_end = avr::hw::db.mem.eeprom_size - 1;
+
+// Lockout-proof floor for the activation window (the oracle's F_CPU/1MHz).
+constexpr std::uint8_t act_min = 16;
+// Post-activation window: the host gets seconds, not milliseconds, mid-session.
+constexpr std::uint8_t comm_window = 200;
+
+constexpr std::uint16_t build_date = 26 * 512 + 7 * 32 + 20;
+
+// Fixed 115200 8N1; the library solves UBRR + U2X from clock and baud.
+constexpr auto baud = avr::uart::detail::solve_baud(16_MHz, 115200_Bd);
+
+// The 16-byte device-info block, streamed out on activation.
+// clang-format off
+[[gnu::progmem]] constexpr std::uint8_t info[16] = {
+    'T', 'S', 'B',
+    build_date & 0xFF, build_date >> 8,
+    0xF3,             // status: native-UART fixed-baud lineage
+    0x1E, 0x95, 0x0F, // ATmega328P signature
+    page / 2,         // page size in words
+    (app_end / 2) & 0xFF, (app_end / 2) >> 8,
+    eeprom_end & 0xFF, eeprom_end >> 8,
+    0xAA, 0xAA,
+};
+// clang-format on
+
+register std::uint16_t g_addr asm("r28");
+register std::uint8_t g_cnt asm("r16");
+register std::uint8_t g_window asm("r7");
+register std::uint8_t g_receiving asm("r6");
+
+const std::uint8_t *flash_ptr(std::uint16_t addr)
+{
+	return reinterpret_cast<const std::uint8_t *>(addr);
+}
+
+// Bounded byte receive (asm 1 of 2): release the one-wire line on a direction
+// change, poll RXC0 under the oracle's nested X-register countdown seeded from
+// g_window (floored against lockout), byte or 0-on-silence in r24. Z survives
+// — the property the store's word loop rides on.
+[[gnu::noinline, gnu::noclone]] std::uint8_t rx()
+{
+	std::uint8_t byte;
+	asm volatile("	tst	%[dir]			\n\t" // already receiving? keep the line released
+	             "	brne	1f			\n\t"
+	             "	ldi	%[b], 0x10		\n\t" // RXEN0 alone: release the line and listen
+	             "	sts	%[ucsr0b], %[b]		\n\t"
+	             "	ser	%[b]			\n\t"
+	             "	mov	%[dir], %[b]		\n\t"
+	             "1:	mov	r27, %[to]		\n\t" // outer countdown high byte = window
+	             "	ori	r27, %[actmin]		\n\t" // lockout-proof floor
+	             "	clr	r26			\n\t"
+	             "2:	ser	%[b]			\n\t"
+	             "3:	lds	%[b], %[ucsr0a]		\n\t"
+	             "	sbrc	%[b], 7			\n\t" // RXC0
+	             "	rjmp	4f			\n\t"
+	             "	dec	%[b]			\n\t"
+	             "	brne	3b			\n\t"
+	             "	sbiw	r26, 1			\n\t"
+	             "	brcc	2b			\n\t"
+	             "	clr	%[b]			\n\t" // silence → 0, which no compare accepts
+	             "	rjmp	5f			\n\t"
+	             "4:	lds	%[b], %[udr0]		\n\t"
+	             "5:					\n\t"
+	             : [b] "=&d"(byte), [dir] "+r"(g_receiving)
+	             : [to] "r"(g_window), [actmin] "M"(act_min), [ucsr0a] "n"(_SFR_MEM_ADDR(UCSR0A)),
+	               [ucsr0b] "n"(_SFR_MEM_ADDR(UCSR0B)), [udr0] "n"(_SFR_MEM_ADDR(UDR0))
+	             : "r26", "r27", "cc");
+	return byte;
+}
+
+// One-wire transmit: take the line (TXEN0 alone) on a direction change with a
+// turn-around guard, put the byte out, hold the line until the whole frame is
+// out (TXC0, not UDRE0), W1C TXC0 by storing the sampled status back (keeps
+// U2X0). Plain C++ — it compiles *smaller* than the oracle's routine.
+[[gnu::noinline, gnu::noclone]] void tx(std::uint8_t byte)
+{
+	if (g_receiving) {
+		g_receiving = 0;
+		hw::ucsr0b::write(hw::ucsr0b::txen0(1));
+		for (std::uint8_t guard = 46; guard; --guard)
+			;
+	}
+	hw::udr0::write(byte);
+	std::uint8_t status;
+	do {
+		status = hw::ucsr0a::read();
+	} while (!(status & hw::ucsr0a::txc0(1).value));
+	hw::ucsr0a::write(status);
+}
+
+// '?', then hand back the host's reply for the callers' one-byte compare.
+[[gnu::noinline, gnu::noclone]] std::uint8_t rcnf()
+{
+	tx(request);
+	return rx();
+}
+
+// One flash byte ← [g_addr++] (the advance right before ret — the
+// global-register rule, see tsb_tricks.cpp).
+[[gnu::noinline, gnu::noclone]] std::uint8_t sflash()
+{
+	std::uint8_t byte = avr::flash_load(flash_ptr(g_addr));
+	++g_addr;
+	return byte;
+}
+
+// One EEPROM byte ← [g_addr++].
+[[gnu::noinline, gnu::noclone]] std::uint8_t eerd()
+{
+	std::uint8_t byte = ee::read(g_addr);
+	++g_addr;
+	return byte;
+}
+
+// One EEPROM byte → [g_addr++].
+[[gnu::noinline, gnu::noclone]] void eewr(std::uint8_t byte)
+{
+	ee::write<off>(g_addr, byte);
+	++g_addr;
+}
+
+// Stream g_cnt flash bytes from g_addr to the host.
+[[gnu::noinline, gnu::noclone]] void sendf()
+{
+	do {
+		tx(sflash());
+	} while (--g_cnt);
+}
+
+// Wait out a running SPM op, then re-open the RWW section — after every page
+// op and before handing over, as the oracle does.
+[[gnu::noinline, gnu::noclone]] void settle()
+{
+	spm::wait();
+	spm::rww_enable<off>();
+}
+
+extern "C" [[noreturn]] void tsb_app(); // the application's reset vector: --defsym=tsb_app=0
+
+[[noreturn]] void appjump()
+{
+	settle();
+	tsb_app();
+}
+
+// Step g_addr one page down and erase that page (the decrement lives here —
+// the global-register rule).
+[[gnu::noinline, gnu::noclone]] void erase_below()
+{
+	g_addr -= page;
+	spm::erase_page<off>(g_addr);
+	settle();
+}
+
+// Erase the whole application, top-down like the oracle: the loop bound is a
+// compare with zero, and g_addr = 0 is handed back for free.
+[[gnu::noinline, gnu::noclone]] void erase_application()
+{
+	g_addr = app_end;
+	do {
+		erase_below();
+	} while (g_addr != 0);
+}
+
+// Stream one host page into the erased flash page at g_addr (asm 2 of 2): the
+// word pair stages in r0:r1 straight from rx (whose register set is known —
+// the cross-call liveness C++ cannot express), Z walks the page and PGWRT
+// programs it. g_addr is left at the next page base.
+[[gnu::noinline, gnu::noclone]] void store_flash()
+{
+	asm volatile("	movw	r30, r28		\n\t" // Z = page base; rx leaves Z live
+	             "	ldi	r20, %[words]		\n\t"
+	             "1:	rcall	%x[rx]			\n\t"
+	             "	mov	r0, r24			\n\t" // word low byte
+	             "	rcall	%x[rx]			\n\t"
+	             "	mov	r1, r24			\n\t" // word high byte
+	             "	ldi	r24, 0x01		\n\t" // SPMEN: buffer the word at Z
+	             "	out	%[spmcsr], r24		\n\t"
+	             "	spm				\n\t"
+	             "	clr	r1			\n\t"
+	             "	adiw	r30, 2			\n\t"
+	             "	dec	r20			\n\t"
+	             "	brne	1b			\n\t"
+	             "	movw	%[base], r30		\n\t" // g_addr = the next page base
+	             "	subi	r30, %[pagelo]		\n\t" // Z back to this page's base
+	             "	sbci	r31, %[pagehi]		\n\t"
+	             "	ldi	r24, 0x05		\n\t" // PGWRT | SPMEN: program the page
+	             "	out	%[spmcsr], r24		\n\t"
+	             "	spm				\n\t"
+	             : [base] "+r"(g_addr)
+	             : [rx] "i"(&rx), [spmcsr] "I"(_SFR_IO_ADDR(SPMCSR)), [words] "M"(page / 2), [pagelo] "M"(page & 0xff),
+	               [pagehi] "M"(page >> 8)
+	             : "r0", "r1", "r20", "r24", "r26", "r27", "r30", "r31", "cc", "memory");
+	settle();
+}
+
+[[noreturn, gnu::noinline]] void run()
+{
+	// A watchdog reset hands straight back to the application, as the
+	// reference loader does, rather than re-entering the bootloader.
+	if (hw::mcusr::wdrf.test())
+		appjump();
+
+	// Lean bring-up from reset state: UCSR0C already reads 8N1, UBRR0H reads
+	// 0, and rx()/tx() raise RXEN0/TXEN0 on first use — only the divisor low
+	// byte and U2X0 need a store. The library still does the datasheet work.
+	static_assert(baud.u2x && baud.ubrr < 256, "lean bring-up writes UBRR0L only, with U2X0");
+	hw::reg<"UBRR0">::write(static_cast<std::uint8_t>(baud.ubrr));
+	hw::ucsr0a::write(hw::ucsr0a::u2x0(1));
+	// General-purpose registers are undefined at power-on (no crt zeroes them);
+	// the direction latch must start "not receiving" so the first rx() enables
+	// the receiver. The reference loader clears its shadow register for the
+	// same reason.
+	g_receiving = 0;
+
+	// Activation: 3×'@', each inside the config page's timeout window (rx
+	// floors it so a corrupt page cannot lock the loader out); anything else —
+	// including silence — hands over.
+	g_window = avr::flash_load(flash_ptr(app_end + 2));
+	for (std::uint8_t k = 3; k; --k)
+		if (rx() != knock)
+			appjump();
+	g_window = comm_window;
+
+	// Password gate (config page from app_end+3, 0xff-terminated; a blank
+	// page is no password). A wrong byte blanks the comparison and drains the
+	// line forever, so a wrong password can never fall through; a 0 requests
+	// emergency erase behind two confirms. On pass the info block goes out;
+	// the emergency path skips it and drops into the command loop.
+	g_addr = app_end + 3;
+	std::uint8_t mask = 0xff;
+	for (;;) {
+		std::uint8_t expected = avr::flash_load(flash_ptr(g_addr)) & mask;
+		++g_addr;
+		if (expected == 0xff) {
+			g_addr = reinterpret_cast<std::uint16_t>(&info[0]);
+			g_cnt = sizeof(info);
+			sendf();
+			break;
+		}
+		std::uint8_t got = rx();
+		if (got == 0) {
+			if (mask == 0)
+				continue;
+			if (rcnf() != confirm || rcnf() != confirm)
+				appjump();
+			erase_application(); // leaves g_addr = 0 for the EEPROM walk
+			do {
+				eewr(0xff);
+			} while (g_addr <= eeprom_end);
+			g_addr = app_end + page;
+			erase_below();
+			break;
+		}
+		if (got != expected)
+			mask = 0;
+	}
+
+	for (;;) {
+		tx(confirm); // Mainloop ready
+		g_addr = 0;
+		switch (rx()) {
+		case 'f': // read application flash, one page per host '!'
+			for (;;) {
+				if (rx() != confirm)
+					break;
+				g_cnt = page;
+				sendf();
+				if (g_addr >= app_end)
+					break;
+			}
+			break;
+		case 'F':                // erase the application, then take pages behind '?'
+			erase_application(); // leaves g_addr = 0, the write start
+			while (rcnf() == confirm)
+				store_flash();
+			break;
+		case 'e': // read EEPROM, one page per host '!', until the host stops
+			for (;;) {
+				if (rx() != confirm)
+					break;
+				g_cnt = page;
+				do {
+					tx(eerd());
+				} while (--g_cnt);
+			}
+			break;
+		case 'E': // take EEPROM pages behind '?'
+			while (rcnf() == confirm) {
+				g_cnt = page;
+				do {
+					eewr(rx());
+				} while (--g_cnt);
+			}
+			break;
+		case 'c': // read the config page
+		read_config:
+			g_addr = app_end;
+			g_cnt = page;
+			sendf();
+			break;
+		case 'C': // replace the config page, then echo it back to verify
+			if (rcnf() != confirm)
+				break;
+			g_addr = app_end + page;
+			erase_below(); // leaves g_addr = app_end, the store target
+			store_flash();
+			goto read_config;
+		default: // 'q' or any other byte runs the application
+			appjump();
+		}
+	}
+}
+
+} // namespace
+} // namespace tsb
+
+// Reset lands here: BOOTRST vectors to the boot section base and .vectors is
+// laid first, so this is the first instruction executed. No crt ran, so set
+// the stack pointer before anything is called.
+extern "C" [[gnu::naked, gnu::used, gnu::section(".vectors")]] void __boot_entry()
+{
+	SP = RAMEND;
+	// The one line of crt this loader needs: compiled code assumes
+	// __zero_reg__ (r1) is 0, and power-on registers are undefined.
+	asm volatile("clr __zero_reg__");
+	tsb::run();
+}

tsb/tsb_pure.cpp

@@ -0,0 +1,308 @@
+// TinySafeBoot on libavr — tier 1: pure, idiomatic C++.
+//
+// A serial flash bootloader for the ATmega328P boot section, reimplementing the
+// TinySafeBoot native-UART fixed-baud protocol on libavr with the full feature
+// set of the hand-written oracle: a watchdog-reset bail, one-wire half-duplex,
+// a config-page activation timeout, the password gate, emergency erase, and
+// config/flash/EEPROM read-write. This variant is written for clarity —
+// well-factored functions, no compiler-specific size hacks, no inline assembly.
+// The one-wire wiring, the flash-resident info block and every SPM/EEPROM lock
+// are libavr's to handle; the only attribute is the naked reset entry that
+// stands in for the absent C runtime.
+
+#include <libavr/libavr.hpp>
+
+#include <avr/io.h> // SP / RAMEND for the crt-free boot entry
+
+using namespace avr::literals;
+namespace spm = avr::spm;
+namespace ee = avr::eeprom;
+
+using dev = avr::device<{.clock = 16_MHz}>;
+// One-wire: RX and TX share the line, exactly as the native-UART TSB expects.
+using serial_t = dev::uart0<{.baud = 115200_Bd, .max_baud_error = 3_pct, .half_duplex = true}>;
+inline constexpr serial_t serial{};
+
+namespace tsb {
+namespace {
+
+// The loader is purely polled — it never enables interrupts — so every SPM and
+// EEPROM lock folds to nothing under this posture.
+constexpr auto off = avr::irq::guard_policy::unused;
+
+// The handshake bytes, identical across every TSB host.
+constexpr std::uint8_t confirm = '!';
+constexpr std::uint8_t request = '?';
+constexpr std::uint8_t knock = '@';
+
+// Boot geometry for the 1 KB boot section (BOOTSZ=10). The page size and the
+// flash/EEPROM extents are the chip database's to know. app_end is the config
+// page (the LASTPAGE holding the app-jump vector, activation timeout and
+// password), one page below the boot section.
+constexpr std::uint16_t page = spm::page_bytes;
+constexpr std::uint16_t boot_bytes = 1024;
+constexpr std::uint16_t app_end = spm::flash_bytes - boot_bytes - page;
+constexpr std::uint16_t eeprom_end = avr::hw::db.mem.eeprom_size - 1;
+
+// Firmware version stamp: YY*512 + MM*32 + DD, the encoding the host decodes.
+constexpr std::uint16_t build_date = 26 * 512 + 7 * 32 + 20;
+
+// The 16-byte device-info block the host reads on activation. A flash_table
+// keeps it in progmem with no .data image (there is no crt to copy one).
+// clang-format off
+inline constexpr std::array<std::uint8_t, 16> info_data = {
+    'T', 'S', 'B',
+    build_date & 0xFF, build_date >> 8,
+    0xF3,             // status byte (native-UART fixed-baud lineage)
+    0x1E, 0x95, 0x0F, // ATmega328P signature
+    page / 2,         // page size in words
+    (app_end / 2) & 0xFF, (app_end / 2) >> 8, // app-flash boundary, words
+    eeprom_end & 0xFF, eeprom_end >> 8,
+    0xAA, 0xAA, // ATmega processor-type marker (bytes 14 == 15)
+};
+// clang-format on
+using info = avr::flash_table<info_data>;
+
+// Blocking byte read/write over the one-wire line: read() releases the line to
+// the receiver, write() takes it and holds it until the frame is out.
+std::uint8_t rx()
+{
+	return serial.read_blocking();
+}
+
+void tx(std::uint8_t byte)
+{
+	serial.write(byte);
+}
+
+const std::uint8_t *flash_ptr(std::uint16_t addr)
+{
+	return reinterpret_cast<const std::uint8_t *>(addr);
+}
+
+// Stream `count` bytes to the host, from flash (LPM) or from EEPROM.
+void send_flash(std::uint16_t addr, std::uint8_t count)
+{
+	while (count--)
+		tx(avr::flash_load(flash_ptr(addr++)));
+}
+
+void send_eeprom(std::uint16_t addr, std::uint8_t count)
+{
+	while (count--)
+		tx(ee::read(addr++));
+}
+
+// Prompt the host with '?' and report whether it answered '!'.
+bool request_confirm()
+{
+	tx(request);
+	return rx() == confirm;
+}
+
+// Stream one page from the host straight into the already-erased flash page at
+// `addr`, filling the SPM word buffer low byte then high — no SRAM staging, so
+// receiving and programming are the same loop.
+void store_flash_page(std::uint16_t addr)
+{
+	for (std::uint16_t i = 0; i < page; i += 2) {
+		std::uint8_t lo = rx();
+		std::uint8_t hi = rx();
+		spm::fill<off>(addr + i, static_cast<std::uint16_t>(lo | (hi << 8)));
+	}
+	spm::write_page<off>(addr);
+	spm::wait();
+}
+
+// Stream one page from the host straight into EEPROM, byte by byte.
+void store_eeprom_page(std::uint16_t addr)
+{
+	for (std::uint16_t i = 0; i < page; ++i)
+		ee::write<off>(addr + i, rx());
+}
+
+// Erase one flash page and wait it out — the erase step shared by the whole-app
+// erase, the config-page rewrite and the emergency wipe.
+void erase_page(std::uint16_t addr)
+{
+	spm::erase_page<off>(addr);
+	spm::wait();
+}
+
+// Erase the whole application, one page at a time, top-down as the reference
+// loader does (unwritten pages stay erased and the host cannot observe the
+// order; the loop bound becomes a compare with zero).
+void erase_application()
+{
+	for (std::uint16_t a = app_end; a != 0;) {
+		a -= page;
+		erase_page(a);
+	}
+	spm::rww_enable<off>();
+}
+
+// The application's reset vector; the linker pins it to 0x0000 (--defsym).
+extern "C" [[noreturn]] void tsb_app();
+
+// Run the application. Any non-command byte, a wrong password, or an idle
+// programmer port lands here.
+[[noreturn]] void appjump()
+{
+	spm::wait(); // make sure any pending SPM finished before handing over
+	tsb_app();
+}
+
+// 'f': stream the application flash back, one page per host '!'. Self-terminates
+// at the application boundary; the host normally stops earlier with a non-'!'.
+void read_flash()
+{
+	for (std::uint16_t a = 0; a < app_end; a += page) {
+		if (rx() != confirm)
+			return;
+		send_flash(a, page);
+	}
+}
+
+// 'e': stream EEPROM back, one page per host '!', until the host stops.
+void read_eeprom()
+{
+	for (std::uint16_t a = 0;; a += page) {
+		if (rx() != confirm)
+			return;
+		send_eeprom(a, page);
+	}
+}
+
+// 'F': erase the whole application first, then take pages the host offers
+// behind '?'.
+void write_flash()
+{
+	erase_application();
+	for (std::uint16_t a = 0; request_confirm(); a += page)
+		store_flash_page(a);
+}
+
+// 'E': take pages the host offers behind '?' into EEPROM.
+void write_eeprom()
+{
+	for (std::uint16_t a = 0; request_confirm(); a += page)
+		store_eeprom_page(a);
+}
+
+// 'C': replace the config page, then echo it back for the host to verify.
+void write_config()
+{
+	if (!request_confirm())
+		return;
+	erase_page(app_end);
+	store_flash_page(app_end);
+	spm::rww_enable<off>();
+	send_flash(app_end, page);
+}
+
+// Emergency erase: wipe the application flash, the EEPROM and the config page.
+// Reachable only from the password gate (a wrong byte can never reach it), so a
+// blank config still leaves the loader recoverable.
+void emergency_erase()
+{
+	erase_application();
+	for (std::uint16_t a = 0; a <= eeprom_end; ++a)
+		ee::write<off>(a, 0xff);
+	erase_page(app_end);
+	spm::rww_enable<off>();
+}
+
+// The password gate. The config page holds the password at app_end+3,
+// terminated by 0xff (a blank page means no password). A byte of 0 requests
+// emergency erase; a wrong byte hangs the loader, still draining the line, so a
+// wrong password can never fall through to the erase.
+enum class gate : std::uint8_t { pass, emergency };
+
+gate password_gate()
+{
+	for (const std::uint8_t *pw = flash_ptr(app_end + 3);; ++pw) {
+		std::uint8_t expected = avr::flash_load(pw);
+		if (expected == 0xff)
+			return gate::pass;
+		std::uint8_t got = rx();
+		if (got == 0)
+			return gate::emergency;
+		if (got != expected)
+			for (;;)
+				rx();
+	}
+}
+
+[[noreturn]] void run()
+{
+	// A watchdog reset hands straight back to the application, as the reference
+	// loader does, rather than re-entering the bootloader.
+	if (avr::hw::mcusr::wdrf.test())
+		appjump();
+
+	avr::init<serial_t>();
+
+	// Activation: the host knocks three '@' inside a window whose length is the
+	// config page's timeout byte (floored so a corrupt page can never lock the
+	// loader out). An idle port times out and boots the application.
+	__uint24 idle = static_cast<__uint24>(avr::flash_load(flash_ptr(app_end + 2)) | 16) << 16;
+	std::uint8_t knocks = 0;
+	while (knocks < 3) {
+		if (auto byte = serial.read())
+			knocks = *byte == knock ? knocks + 1 : 0;
+		else if (--idle == 0)
+			appjump();
+	}
+
+	switch (password_gate()) {
+	case gate::pass:
+		send_flash(reinterpret_cast<std::uint16_t>(info::storage.data()), info::size());
+		break;
+	case gate::emergency:
+		if (!request_confirm() || !request_confirm())
+			appjump();
+		emergency_erase();
+		break;
+	}
+
+	for (;;) {
+		tx(confirm); // Mainloop ready
+		switch (rx()) {
+		case 'f':
+			read_flash();
+			break;
+		case 'F':
+			write_flash();
+			break;
+		case 'e':
+			read_eeprom();
+			break;
+		case 'E':
+			write_eeprom();
+			break;
+		case 'c':
+			send_flash(app_end, page);
+			break;
+		case 'C':
+			write_config();
+			break;
+		default:
+			appjump(); // 'q' or any other byte runs the application
+		}
+	}
+}
+
+} // namespace
+} // namespace tsb
+
+// Reset lands here: BOOTRST vectors to the boot section base and .vectors is
+// laid first, so this is the first instruction executed. No crt ran, so set the
+// stack pointer before anything is called.
+extern "C" [[gnu::naked, gnu::used, gnu::section(".vectors")]] void __boot_entry()
+{
+	SP = RAMEND;
+	// The one line of crt this loader needs: compiled code assumes
+	// __zero_reg__ (r1) is 0, and power-on registers are undefined.
+	asm volatile("clr __zero_reg__");
+	tsb::run();
+}

tsb/tsb_tricks.cpp

@@ -0,0 +1,363 @@
+// TinySafeBoot on libavr — tier 2: C++ with compiler trickery, no assembly.
+//
+// The full TinySafeBoot feature set — watchdog bail, one-wire half-duplex,
+// config-page activation timeout, password gate, emergency erase, and
+// config/flash/EEPROM read-write — in pure C++, 526 bytes: 14 over the 512-byte
+// boot section the hand-written oracle fits, from 168 over at this tier's first
+// floor. The structure mirrors the oracle's: a handful of tiny noinline
+// primitives sharing one whole-loader register allocation, expressed as global
+// register variables so no helper ever saves, spills, or reloads any of it.
+//
+// The register protocol (all call-saved, so calls preserve them by ABI):
+//   Y (r28:r29)  g_addr      the walked flash/EEPROM address — adiw-able
+//   r16          g_cnt       byte countdown of the running block — ldi-able
+//   r7           g_window    rx timeout, roughly 30 ms units at 16 MHz
+//   r6           g_receiving one-wire direction latch, cleared at bring-up
+//                            (power-on registers are undefined)
+//
+// GCC 16.1 miscompiles stores into global register variables: an update whose
+// remaining uses all hide inside callees is deleted whenever a CALL follows it
+// before any jump/ret (the backend's liveness walk lumps fixed registers with
+// call-clobbered ones — minimal repro in libavr's
+// local/scratch/probes/gcc-avr-globalreg-repro.cpp, lessons.md entry). Every
+// g_* update below therefore sits where a *local* read or a jump/ret follows
+// it — the helpers advance g_addr immediately before returning, and rx()
+// re-floors the window on every call instead of storing the floored value
+// once. The layout is load-bearing; do not "simplify" it.
+//
+// The wire protocol is strict request/response, which is what makes the shared
+// line safe: the device drives it only between a received command and its
+// reply, and releases it (RXEN0 only) whenever it waits.
+
+#include <libavr/libavr.hpp>
+
+#include <avr/io.h> // SP / RAMEND for the crt-free boot entry
+
+using namespace avr::literals;
+namespace spm = avr::spm;
+namespace ee = avr::eeprom;
+namespace hw = avr::hw;
+
+namespace tsb {
+namespace {
+
+// The loader is purely polled — it never enables interrupts — so every SPM and
+// EEPROM lock folds to nothing under this posture.
+constexpr auto off = avr::irq::guard_policy::unused;
+
+constexpr std::uint8_t confirm = '!';
+constexpr std::uint8_t request = '?';
+constexpr std::uint8_t knock = '@';
+
+// Boot geometry for the 1 KB boot section (BOOTSZ=10); the page size and the
+// flash/EEPROM extents are the chip database's to know. app_end is the config
+// page (TSB's LASTPAGE), one page below the boot section.
+constexpr std::uint16_t page = spm::page_bytes;
+constexpr std::uint16_t boot_bytes = 1024;
+constexpr std::uint16_t app_end = spm::flash_bytes - boot_bytes - page;
+constexpr std::uint16_t eeprom_end = avr::hw::db.mem.eeprom_size - 1;
+
+// Lockout-proof floor for the activation window (the oracle's F_CPU/1MHz).
+constexpr std::uint8_t act_min = 16;
+// Post-activation window: the host gets seconds, not milliseconds, mid-session.
+constexpr std::uint8_t comm_window = 200;
+
+constexpr std::uint16_t build_date = 26 * 512 + 7 * 32 + 20;
+
+// Fixed 115200 8N1; the library solves UBRR + U2X from clock and baud.
+constexpr auto baud = avr::uart::detail::solve_baud(16_MHz, 115200_Bd);
+
+// The 16-byte device-info block, streamed out on activation.
+// clang-format off
+[[gnu::progmem]] constexpr std::uint8_t info[16] = {
+    'T', 'S', 'B',
+    build_date & 0xFF, build_date >> 8,
+    0xF3,             // status: native-UART fixed-baud lineage
+    0x1E, 0x95, 0x0F, // ATmega328P signature
+    page / 2,         // page size in words
+    (app_end / 2) & 0xFF, (app_end / 2) >> 8,
+    eeprom_end & 0xFF, eeprom_end >> 8,
+    0xAA, 0xAA,
+};
+// clang-format on
+
+register std::uint16_t g_addr asm("r28");
+register std::uint8_t g_cnt asm("r16");
+register std::uint8_t g_window asm("r7");
+register std::uint8_t g_receiving asm("r6");
+
+const std::uint8_t *flash_ptr(std::uint16_t addr)
+{
+	return reinterpret_cast<const std::uint8_t *>(addr);
+}
+
+// Bounded byte receive, the oracle's shape: release the one-wire line on a
+// direction change, poll RXC0 under nested countdowns, 0 on silence. The 0
+// then falls through every compare — not a knock, not a confirm, not a
+// command — so a silent host unwinds the loader to the application from
+// anywhere, and a mid-session cable pull cannot wedge it.
+[[gnu::noinline, gnu::noclone]] std::uint8_t rx()
+{
+	if (!g_receiving) {
+		g_receiving = 1;
+		hw::ucsr0b::write(hw::ucsr0b::rxen0(1)); // RXEN0 alone: release and listen
+	}
+	// act_min ORs in here, per call, not once into g_window at setup — the
+	// one placement the global-register-store miscompile cannot delete.
+	std::uint16_t outer = static_cast<std::uint16_t>(g_window | act_min) << 8;
+	do {
+		std::uint8_t fine = 0;
+		do {
+			auto status = hw::ucsr0a::read();
+			if (status & hw::ucsr0a::rxc0(1).value)
+				return hw::udr0::read();
+		} while (--fine);
+	} while (--outer);
+	return 0;
+}
+
+// One-wire transmit: take the line (TXEN0 alone — the receiver must be off
+// while driving) on a direction change, with a turn-around guard so a shorted
+// peer can switch first; then hold the line until the whole frame is out
+// (TXC0, not UDRE0 — the stop bit must be on the wire before a caller may
+// release the line), and W1C TXC0 by storing the sampled status back, which
+// keeps U2X0.
+[[gnu::noinline, gnu::noclone]] void tx(std::uint8_t byte)
+{
+	if (g_receiving) {
+		g_receiving = 0;
+		hw::ucsr0b::write(hw::ucsr0b::txen0(1));
+		for (std::uint8_t guard = 46; guard; --guard)
+			;
+	}
+	hw::udr0::write(byte);
+	std::uint8_t status;
+	do {
+		status = hw::ucsr0a::read();
+	} while (!(status & hw::ucsr0a::txc0(1).value));
+	hw::ucsr0a::write(status);
+}
+
+// '?', then hand back the host's reply for the callers' one-byte compare.
+[[gnu::noinline, gnu::noclone]] std::uint8_t rcnf()
+{
+	tx(request);
+	return rx();
+}
+
+// One flash byte ← [g_addr++] (the advance right before ret — see header).
+[[gnu::noinline, gnu::noclone]] std::uint8_t sflash()
+{
+	std::uint8_t byte = avr::flash_load(flash_ptr(g_addr));
+	++g_addr;
+	return byte;
+}
+
+// One EEPROM byte ← [g_addr++].
+[[gnu::noinline, gnu::noclone]] std::uint8_t eerd()
+{
+	std::uint8_t byte = ee::read(g_addr);
+	++g_addr;
+	return byte;
+}
+
+// One EEPROM byte → [g_addr++].
+[[gnu::noinline, gnu::noclone]] void eewr(std::uint8_t byte)
+{
+	ee::write<off>(g_addr, byte);
+	++g_addr;
+}
+
+// Stream g_cnt flash bytes from g_addr to the host.
+[[gnu::noinline, gnu::noclone]] void sendf()
+{
+	do {
+		tx(sflash());
+	} while (--g_cnt);
+}
+
+// Wait out a running SPM op, then re-open the RWW section — after every page
+// op and before handing over, as the oracle does.
+[[gnu::noinline, gnu::noclone]] void settle()
+{
+	spm::wait();
+	spm::rww_enable<off>();
+}
+
+extern "C" [[noreturn]] void tsb_app(); // the application's reset vector: --defsym=tsb_app=0
+
+[[noreturn]] void appjump()
+{
+	settle();
+	tsb_app();
+}
+
+// Step g_addr one page down and erase that page. The decrement lives in here,
+// before the erase's own use of it, not in the caller's loop where a following
+// call would get it deleted (see header).
+[[gnu::noinline, gnu::noclone]] void erase_below()
+{
+	g_addr -= page;
+	spm::erase_page<off>(g_addr);
+	settle();
+}
+
+// Erase the whole application, top-down like the oracle: the loop bound is a
+// compare with zero, and g_addr = 0 — the value every caller wants next — is
+// handed back for free.
+[[gnu::noinline, gnu::noclone]] void erase_application()
+{
+	g_addr = app_end;
+	do {
+		erase_below();
+	} while (g_addr != 0);
+}
+
+// Stream one host page into the erased flash page at g_addr (SPM word buffer,
+// low byte then high) — no SRAM staging, receive and program are one loop.
+// g_addr is left at the next page base.
+[[gnu::noinline, gnu::noclone]] void store_flash()
+{
+	g_cnt = page / 2;
+	do {
+		std::uint16_t word = rx();
+		word |= static_cast<std::uint16_t>(rx()) << 8;
+		spm::fill<off>(g_addr, word);
+		g_addr += 2;
+	} while (--g_cnt);
+	spm::write_page<off>(g_addr - page);
+	settle();
+}
+
+[[noreturn, gnu::noinline]] void run()
+{
+	// A watchdog reset hands straight back to the application, as the
+	// reference loader does, rather than re-entering the bootloader.
+	if (hw::mcusr::wdrf.test())
+		appjump();
+
+	// Lean bring-up from reset state: UCSR0C already reads 8N1, UBRR0H reads
+	// 0, and rx()/tx() raise RXEN0/TXEN0 on first use — only the divisor low
+	// byte and U2X0 need a store. The library still does the datasheet work.
+	static_assert(baud.u2x && baud.ubrr < 256, "lean bring-up writes UBRR0L only, with U2X0");
+	hw::reg<"UBRR0">::write(static_cast<std::uint8_t>(baud.ubrr));
+	hw::ucsr0a::write(hw::ucsr0a::u2x0(1));
+	// General-purpose registers are undefined at power-on (no crt zeroes them);
+	// the direction latch must start "not receiving" so the first rx() enables
+	// the receiver. The reference loader clears its shadow register for the
+	// same reason.
+	g_receiving = 0;
+
+	// Activation: 3×'@', each inside the config page's timeout window (rx
+	// floors it so a corrupt page cannot lock the loader out); anything else —
+	// including silence — hands over.
+	g_window = avr::flash_load(flash_ptr(app_end + 2));
+	for (std::uint8_t k = 3; k; --k)
+		if (rx() != knock)
+			appjump();
+	g_window = comm_window;
+
+	// Password gate (config page from app_end+3, 0xff-terminated; a blank
+	// page is no password). A wrong byte blanks the comparison and drains the
+	// line forever, so a wrong password can never fall through; a 0 requests
+	// emergency erase behind two confirms. On pass the info block goes out;
+	// the emergency path skips it and drops into the command loop.
+	g_addr = app_end + 3;
+	std::uint8_t mask = 0xff;
+	for (;;) {
+		std::uint8_t expected = avr::flash_load(flash_ptr(g_addr)) & mask;
+		++g_addr;
+		if (expected == 0xff) {
+			g_addr = reinterpret_cast<std::uint16_t>(&info[0]);
+			g_cnt = sizeof(info);
+			sendf();
+			break;
+		}
+		std::uint8_t got = rx();
+		if (got == 0) {
+			if (mask == 0)
+				continue;
+			if (rcnf() != confirm || rcnf() != confirm)
+				appjump();
+			erase_application(); // leaves g_addr = 0 for the EEPROM walk
+			do {
+				eewr(0xff);
+			} while (g_addr <= eeprom_end);
+			g_addr = app_end + page;
+			erase_below();
+			break;
+		}
+		if (got != expected)
+			mask = 0;
+	}
+
+	for (;;) {
+		tx(confirm); // Mainloop ready
+		g_addr = 0;
+		switch (rx()) {
+		case 'f': // read application flash, one page per host '!'
+			for (;;) {
+				if (rx() != confirm)
+					break;
+				g_cnt = page;
+				sendf();
+				if (g_addr >= app_end)
+					break;
+			}
+			break;
+		case 'F':                // erase the application, then take pages behind '?'
+			erase_application(); // leaves g_addr = 0, the write start
+			while (rcnf() == confirm)
+				store_flash();
+			break;
+		case 'e': // read EEPROM, one page per host '!', until the host stops
+			for (;;) {
+				if (rx() != confirm)
+					break;
+				g_cnt = page;
+				do {
+					tx(eerd());
+				} while (--g_cnt);
+			}
+			break;
+		case 'E': // take EEPROM pages behind '?'
+			while (rcnf() == confirm) {
+				g_cnt = page;
+				do {
+					eewr(rx());
+				} while (--g_cnt);
+			}
+			break;
+		case 'c': // read the config page
+		read_config:
+			g_addr = app_end;
+			g_cnt = page;
+			sendf();
+			break;
+		case 'C': // replace the config page, then echo it back to verify
+			if (rcnf() != confirm)
+				break;
+			g_addr = app_end + page;
+			erase_below(); // leaves g_addr = app_end, the store target
+			store_flash();
+			goto read_config;
+		default: // 'q' or any other byte runs the application
+			appjump();
+		}
+	}
+}
+
+} // namespace
+} // namespace tsb
+
+// Reset lands here: BOOTRST vectors to the boot section base and .vectors is
+// laid first, so this is the first instruction executed. No crt ran, so set
+// the stack pointer before anything is called.
+extern "C" [[gnu::naked, gnu::used, gnu::section(".vectors")]] void __boot_entry()
+{
+	SP = RAMEND;
+	// The one line of crt this loader needs: compiled code assumes
+	// __zero_reg__ (r1) is 0, and power-on registers are undefined.
+	asm volatile("clr __zero_reg__");
+	tsb::run();
+}