Implements the first working feature: the device records audio to the microSD
card, toggled by the button, with LED status and per-recording JSON metadata.
What changed:
- firmware/src/audio.{h,cpp}: mic capture via the core-bundled ESP_I2S. Dev board
uses I2S standard mode (INMP441/ICS-43434); XIAO uses PDM mode (onboard mic).
Presents 16-bit PCM mono to callers regardless of board.
- firmware/src/storage.{h,cpp}: microSD on a dedicated HSPI bus + a streaming
WavWriter that writes a 44-byte PCM header and patches RIFF/data sizes on close;
plus sidecar JSON metadata writer.
- firmware/src/recorder.{h,cpp}: idle/recording state machine; creates
/recordings/<id>.wav, pumps mic chunks in on update(), finalises + writes
<id>.json (Recording schema from api/openapi.yaml) on stop.
- firmware/src/ux.{h,cpp}: debounced button (short press toggles) + status LED
patterns (idle/recording/error), active-low aware.
- firmware/src/main.cpp: wires ux + recorder; loop toggles on button and drains
the mic while recording.
- firmware/include/audio_config.h: 16 kHz mono 16-bit, chunk size, rec dir.
- firmware/include/pins.h: added XIAO PDM mic + onboard SD pins, LED active-low flag.
- state/: TODO, ARCHITECTURE, NOTES updated for M1 and the deferred follow-ups.
Why:
- Recording is the foundation every later milestone (transfer, upload, transcription)
builds on. Kept dependency-free (only core-bundled ESP_I2S + SD) for simple CI builds.
Notes:
- Not compiled locally (no PlatformIO on the dev host) or hardware-verified; Forgejo
Actions CI builds both board profiles. Follow-ups tracked in state/TODO.md:
INMP441 16-bit level calibration, and real NTP timestamps (ids are uptime-based
until M2 brings WiFi/NTP).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Laurence
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