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>
