avrdude programs Intel-HEX, not ELF, and the build produced only ELFs — so
flashing a loader to a real chip meant running objcopy by hand. add_hex_output()
hangs a POST_BUILD objcopy on each loader image: the three tsb tiers through
add_tsb_variant, pureboot, and the re-timed pureboot9. .eeprom is dropped, being
its own avrdude update.
It uses the toolchain file's CMAKE_OBJCOPY rather than a hardcoded path, so
every chip preset emits hex, not just the mega. pbapp keeps its ELF alone: the
update test converts it to a raw binary itself, and it is not a flashing target.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
check_pi.py asserts the two link-time facts position independence rests on
(no absolute jmp/call; the info block within the image's first 256 bytes);
the size gates drop to 510 on the tinies for the trampoline word.
New per-chip tests beside the reworked protocol test: the planner units
(programming orders and their recovery properties, the surgery, staging
composition, boot-fuse decode, and the update preflight's error/warning
matrix over synthetic fuse bytes), the relocated-copy sweep (the identical
image installed one slot lower serves the full command set — the PI
acceptance test, and the one that caught the temporary-buffer trap), and
the self-update end-to-end: --update-loader to a re-timed build
(pureboot9, byte-different by PUREBOOT_TIMEOUT alone), then every
power-fail phase killed mid-write, restarted from the runner's flash dump,
and completed by a re-run with the application intact throughout. The mega
rounds run the BOOTRST-unprogrammed profile: the fixture application's 'L'
jump is the application-owned loader entry that profile relies on.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The image now runs from any 512-byte slot with every command intact:
control flow stays PC-relative, the write guard keys on the running slot
(the return-address anchor, computed once), the info block is addressed
from that same anchor as a byte pair (no absolute 16-bit address in the
image), and the application jump is an indirect call through a noipa-
laundered pointer to the absolute entry. 'J' — jump to a wire word
address, the one transfer primitive — replaces 'G': the host knows the
application entry from the info block, and moving between loader copies
needs arbitrary targets. The activation window is a compile-time 8 s
(PUREBOOT_TIMEOUT overrides), counted as a single calibrated poll loop.
A refused page no longer poisons the write-once temporary buffer (a real
silicon trap: the next write would program the drained data): every page
write discards the buffer first — CTPB on the tinies, on the mega the same
RWWSRE store that re-enables RWW after programming. The tinies' post-op
busy-waits go with it: their CPU halts through page erase and write.
488 / 502 / 504 B on t13a / t85 / mega — under the tinies' 510-byte budget,
whose last slot word is the host-managed trampoline: the resident's holds
the application entry, a staging copy's the jump through which an abandoned
update still times out into a loader.
The host tool updates the loader with itself: --update-loader installs the
identical image one slot below the resident, jumps into it, lets it rewrite
the resident, and restores the staging region from a state file — each
phase idempotent off the flash state, resumable after any interruption
(t13a: the staging slot carries the reset vector, written last in and
first out; t85: word 0 redirected around the resident rewrite; mega:
fuse-matrix preflight with a hard BOOTSZ gate and --assume-fuses for
simulators). Application flashing recovers by reset from any interruption:
patched page 0 and trampoline first, erase descending, and a walk-region
refusal behind --force on BOOTRST-below-loader megas.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Cancel the GPIO bridge's cycle timers with the state they drive: avr_reset
drops the TX latch, whose falling edge starts a spurious decode before
bridge_reset runs, and the stale sampler then interleaves with the loader's
first real answer through the shared shift state — the first post-reset
replies came back corrupted and the knock retries burned the activation
window into the application.
Wrap the mega's registered flash ioctl to re-dispatch page erases with Z
masked to the page boundary: simavr's PGERS handler erases spm_pagesize
bytes from Z & ~1 (its PGWRT path masks correctly), wiping the neighbouring
page when Z sits past the page start, which hardware permits (§26.8.1).
Model the write-once temporary buffer in the tiny NVM module — silicon
refuses a second load per word until the buffer clears, and a last-write-
wins model masks real firmware bugs.
Optional arguments select the reset vector (the mega's fuse profiles) and a
raw flash image to resume from (power-fail tests re-enter a dumped state).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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>
A stray __pycache__/*.pyc from a local test run got swept into the
previous commit's git add. Untracked and gitignored.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
pureboot.py (Python stdlib only): images as raw binary or Intel HEX,
flash and EEPROM programming with read-back verify, erase composites,
fuse and info readout, activation-timeout configuration, and the
tinies' reset-vector surgery — the trampoline word below the loader,
page 0 written last.
The test spawns a simavr device (pureboot_device.c) — the mega's USART
as a pty; on the tinies a cycle-timed GPIO<->pty bridge for the polled
software UART plus the NVM module simavr's tiny cores lack (their SPM
opcode ioctls into a void and silently does nothing) — and drives it
with the real tool: knock from reset (erased-flash walk on the tinies),
program and verify both memories, timeout write, session reconnect, an
external reset through the patched vector, hand-over, and the fixture
application's banner. Results are cross-checked against ground-truth
memory dumps and an independent decode of the surgery's rjmp words,
red-verified against a sabotaged encoder.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
No inline assembly, no global register variables; libavr does the
datasheet work. The device speaks primitives — flash read/page-program,
EEPROM read/write, fuse read, info block, EEPROM-resident activation
timeout, hand-over — and verify, erase, reset-vector surgery, and
timeout configuration live in the host tool. 490 B on the ATtiny13A,
510 B on the ATtiny85, 484 B on the ATmega328P, each linked into the
top 512 bytes of flash; per-chip size tests gate all three.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The second pass concluded the 168 B tricks->asm gap was per-call ABI
cost. Most of it was structure. Rebuilt around the oracle's own shape —
argless noinline primitives over a whole-loader call-saved register
protocol (g_addr in Y, count r16, window r7, direction latch r6), a
top-down erase_below whose loop tests against zero and hands callers
g_addr = 0 for free, bounded rx everywhere (a silent host unwinds to
the app from any state, as the oracle does), and a named tsb_app entry
that --pmem-wrap-around=32k relaxes to the wrapped rjmp:
tsb_asm 510 B in the 512 B section (oracle: 500), C++ except rx
and the page-store loop — the two routines whose remaining
cost is the calling convention itself (~30 asm lines, was
~280)
tsb_tricks 526 B, no assembly at all (was 666)
tsb_pure 836 B, still one readable function per command (was 842)
Every g_* update placement works around a GCC 16.1 wrong-code bug
(stores into global register variables deleted when only callees read
them — repro and rules in libavr dev/lessons.md). Also fixes two
latent hardware bugs all earlier tiers carried, masked by simavr's
zeroed register file: the crt-less entries never established
__zero_reg__ = 0, and the direction latch was read before written —
power-on registers are undefined.
All tiers full oracle feature parity, protocol tests green in both
libavr modes, .text byte-identical across modes.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
tricks 778->666: always_inline every single-call handler into the
[[noreturn]] reset entry (which pays no prologue, so their push/pop of
call-saved registers vanishes), walk the page pointer in Y (adiw, base
recovered as g_addr-page) instead of recomputing Z=base+offset, bring
the UART up in the two registers that are not already at their reset
value, and seed the activation counter as __uint24.
pure 896->842: TU-local internal linkage (proper hygiene, and it lets
the compiler inline the one-call handlers), a byte-wide activation
count, __uint24 timeout. Still one readable function per command.
asm unchanged at 498: its C++-expressible parts are already C++; the
core stays asm (the 666 B all-tricks tier is 168 B over — per-call ABI
tax, not a feature). All three cross-mode byte-identical, protocol green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
asm 502->498 B (below the oracle's 500): the stack bring-up moves to plain C++,
and a register is reserved for the config-page high byte instead of reloading it
at each app-flash-boundary compare. tricks 808->778 B: shared erase/rww helpers
plus the libavr half-duplex W1C fix. pure 950->896 B and no SRAM: streams
rx->SPM/EEPROM instead of staging a 128 B page buffer. All three keep full oracle
feature parity and stay byte-identical across modes; protocol tests (round-trip +
password + emergency erase) green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Each scenario group now runs on its own freshly-reset device: the round-trip
on a blank config page, plus a password-config device that must be sent the
password after the knock to activate, and an emergency-erase device where a
0-byte + two confirms wipes flash, EEPROM and the config page (verified by
reading all three back as 0xff). All three tiers pass every group.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Both tiers gain the features the asm tier already carries — one-wire
half-duplex (via libavr's new .half_duplex), the config-page activation
timeout, and emergency erase (password \0 + double-confirm wipes flash,
EEPROM and the config page) — on top of the watchdog bail, password gate and
config/flash/EEPROM read-write they already had. pure stays idiomatic
(flash_table info block, one function per command) at 950 B; tricks keeps its
compiler trickery (call-saved global-register page walk, unified runtime-flag
paths pinned noinline/noclone, streaming stores, arithmetic command decode)
at 808 B. Both byte-identical across generated and reflect modes; the size
gradient across the three tiers is now 502 / 808 / 950 B.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Rewrite the inline-asm tier so it matches the hand-written fixed-baud oracle's
feature set inside the 512 B boot section: watchdog-reset bail, one-wire
half-duplex (RXEN/TXEN toggled per direction, TX turnaround guard),
config-page activation timeout, the password gate (wrong byte hangs draining
the UART), emergency erase (password \0 + double-confirm wipes flash, EEPROM
and the config page), and config/flash/EEPROM read-write. Every geometry,
baud and info-block constant comes from libavr consteval; only the dense
control flow is hand-written. 502 B, byte-identical across generated and
reflect modes.
Test harness: seed the config page from TSB_CONFIG so the password and
emergency-erase paths are exercisable, and clear simavr's AVR_UART_FLAG_POLL_
SLEEP — a host-CPU-saving usleep(1)-per-idle-poll hack that models no hardware
and paces a one-wire loader (which releases TX between bytes) in real time,
distorting protocol timing.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The Seed Robotics native-UART fixed-baud TinySafeBoot (GPLv3), reference
only — not built. Assembles to 500 B with the full feature set, proving
≤512 B and full feature parity are simultaneously reachable. Also drops the
stale empty stk500v2/ leftover.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Direct register access now reads through the named surface
(hw::mcusr::wdrf.test(), hw::ucsr0b::write(...)) instead of the string form,
matching how libavr itself is written. Zero-overhead: pure 740 B, tricks 658 B,
asm 508 B unchanged, all byte-identical across modes, protocol green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The showcase tier now leans on the helpers it fed back instead of reaching under
them: the info block is an avr::flash_table (no raw [[gnu::progmem]]), a page is
filled with spm::fill(addr, span) (no hand-packed lo|hi<<8 loop), and the
WDT-reset bail reads field<"MCUSR","WDRF">::test() (no read() & {}(1).value).
Zero-overhead throughout: .text stays 740 B, byte-identical across generated and
reflect modes, protocol test green. The info block streams through the existing
address-based send_flash rather than a range-for over the flash_table — the
range-for is a distinct loop that cannot share the loader's one flash streamer,
so it would add 14 B for no functional gain.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
main carried the whole pre-libavr tree beside the port: the other-bootloader
directories (blink, stk500v2), the Atmel Studio solution/project, and — dead in
the tsb dir itself — four submodule links to the superseded io/flash/uart/type
libraries the libavr sources never include. None are build inputs; CMake drives
the three variants through FetchContent. master keeps the full legacy tree
untouched.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The -O3 leak is fixed upstream (cmake/release-os.cmake via CMAKE_PROJECT_INCLUDE),
so the port no longer needs its own string(REPLACE); a Release build is -Os
through the toolchain file. Verified: all three variants build at their sizes
(508/658/740) and pass the size + protocol ctest.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The native-UART fixed-baud TinySafeBoot protocol, ported onto libavr as a
crt-free boot-section loader, in three variants that trade clarity for size:
tsb_pure 740 B idiomatic C++: SRAM page buffer, separate flash/EEPROM
leaves, shared framing; the polled `unused` guard posture.
tsb_tricks 658 B unified runtime-flag paths (noinline/noclone), call-saved
global-register page walk — attributes only, no asm.
tsb_asm 508 B streaming store + hand-rolled UART/SPM/EEPROM/erase loops;
fits the 512 B boot section (BOOTSZ=11). Trims the optional
password gate and WDT-reset bail — unreachable in C++ with
both (hand-asm is ~15 % denser). Tiers 1-2 keep them and
live in the 1 KB section they fit.
All three are .text byte-identical across libavr's generated and reflect modes.
The CMake build strips the leaked -O3 (a Release build is silently -O3, not the
-Os this loader is measured against) and gates each variant's size against its
section. A simavr harness (test/device.c + test/tsbtest.py) drives the real wire
protocol over a pty and flashes the device; the size and protocol tests run in
ctest. Verified byte-for-byte against the reference tsbloader_adv (C#/mono):
activate, read info, flash write + verify.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
