BlackMark
2cc540c6a1
Hardware testing found that a lone calibration pulse wedged the autobaud loader: run() budgeted only the start-edge wait in measure(), and the rx() that read the knock behind it was unbudgeted, so one stray low pulse held an unattended device in the loader and the application never ran. Bound the whole activation — an expired knock budget returns a byte that cannot be the knock, so control falls back into the budgeted measure() and an idle line boots the app there. That fix costs ~22 B, which neither version under review could absorb: the pure one goes 508 -> 530 on the 1284P and the register one 512 -> 534, both over a 512 B slot. Their margin was never spare capacity, it was the space the missing fix should have occupied. So the choice between them is moot; both are kept for the record and no longer built. pureboot_autobaud_uni.cpp replaces them at 464 B. It is pureboot 5: one read command and one write command over named spaces (G/g, sel8, addr16, n8) instead of four per-memory bodies, which collapses four transfer loops into one. The selector's high nibble carries flash's bank, so the shared cursor stays 16 bits and no command speaks word addresses. Three things fall out of the freed space: RAM read/write — the missing feature, and with it arbitrary I/O access, since AVR maps peripherals into the data space; host-issued SPM, so W's hardcoded erase/write/RWW tail becomes three writes to a space and any SPM operation is reachable; and W on the same selector-and-address decode as everything else. Strictly pure throughout: no inline asm, no global register variable, and no GPIOR either — the unit lives in a .noinit static, so the loader claims no chip resource and the chips without GPIOR stop being a special case. pureboot.py speaks both generations, keyed on the version, so the fixed-baud path is untouched; --peek/--poke reach the new data space. pbautobaud.py adds a RAM round-trip and a regression for the hang: a lone pulse must still let the app boot. All 37 chips plus the 12-preset reflect spot set build and size-test green, 444-466 B, worst case 46 B under budget. Sim suites 100%: 1284P 17/17, 328P 23/23. Only real-hardware acceptance remains (pureboot/autobaud.md). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
7.3 KiB
7.3 KiB