The XIAO stopped answering on 10-07 ("No response from meshcore
node" for many starts in a row). MeshCore's serial parser reads '<'
and a two-byte length, then waits for that many bytes with no time
limit, so one lost or damaged byte can make it swallow up to 65,535
bytes, and MeshTerm sends only 16 per start. Reproduced on the
PicoCalc: a half frame blocked two APP_STARTs until 600 filler bytes
arrived. meshcore-frame-timeout.patch drops a frame after 200 ms of
silence on the line (bytes queued while the loop was busy still
count), and build-firmware.sh applies it after meshcore-uart1.patch.
Upstream dev and main still have the old parser.
Flashing the XIAO with the new firmware, following the guide as
written, found these problems, now corrected:
- Step 11: `pip install platformio` failed (no pip outside a venv on
this PC), and it fails on externally managed Pythons or lands in an
active venv. The guide now uses the official installer only, and
build-firmware.sh and flash.py find pio in ~/.platformio/penv, so
nobody edits the PATH. uf2conv runs on PlatformIO's Python, because
a bare `python` is missing on many Linux systems.
- Step 12: the script's last line said to double-tap reset first;
flash.py touches the XIAO itself, and a wired XIAO's reset button is
inside the case.
- Step 13: this XIAO's bootloader has only a serial port, and flash.py
printed a pio command for the user to run "from your MeshCore
checkout", with pio not on the PATH. flash.py now does the serial
DFU upload itself (54 s here). Without pyserial, it runs itself
again with PlatformIO's Python instead of skipping the touch.
- A wired XIAO's USB power goes backward into the Lyra through the
3V3 wire (JP confirmed it on the bench). Step 13 now applies only
before wiring, and a new Day-to-day procedure updates the firmware
of a wired radio: poweroff, switch off, open, batteries out, flash.
After the flash, the radio kept its identity, MeshTerm's info command
connected, and an APP_START after a half frame and 0.5 s of silence
got its reply at once.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Jean-Pierre MartineauandClaude Opus 5.5
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