BlackMark
04c04abe3e
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>
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 matches this bar; tsb_pure
and tsb_tricks implement the same protocol at larger sizes in the 1 KB section,
trading bytes for readability.
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.