Extends the existing FM/DAB ANTCAP EEPROM persistence pattern
(Eeprom24aa::writeFmAntCap/writeDabAntCap) to the crystal trim found by
POST /api/tuner/xtal-calibrate, which previously only applied live and
was lost on every reboot.
- Eeprom24aa gains readXtalCalibration()/writeXtalCalibration() at word
addresses 0x02 (ibias), 0x03 (ctun), 0x04-0x07 (xtalFreqHz,
big-endian), right after the existing FM/DAB ANTCAP bytes.
- HardwareBootstrap::boot() now boots ADAU1701 before Si4684 (needed so
the EEPROM read, which borrows ADAU1701's I2C bus, can happen before
Si4684's boot() call, which takes the crystal trim as an argument),
loads the saved trim if present, and falls back to the compiled-in
defaults (ibias=72, ctun=0, xtalFreqHz=19199750) otherwise.
- POST /api/tuner/xtal-calibrate now persists every successful live
recalibration automatically ("persisted":true/false in the response)
via a new saveXtalCalibration()/net::AntennaCalibration::saveXtal
bridge, mirroring the ANTCAP save pattern.
Verified live: boot log confirms "Xtal not calibrated" before the first
save, "Xtal calibration loaded: ibias=72 ctun=0 xtal_freq_hz=19199750"
after, surviving a reboot; DAB/FM tuning unaffected (DAB CNR 17-19dB,
locked).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Root cause of FM/DAB "stonata" audio: xtalCtun=31/nominal XTAL_FREQ
defaults were never measured against this board's actual crystal
(Abracon ABM8-19.200MHZ-10-1-U-T, CL=10pF, two external 15pF load
caps). Fixed via CTUN trim by ear (31->0) plus a new live calibration
loop that reads the Si4684's own FM_RSQ FREQOFF field (broadcast
carriers are GPS-locked, so it's a free precision frequency reference)
to trim XTAL_FREQ with no lab equipment. Converged to CTUN=0,
XTAL_FREQ=19199750 Hz, residual -3/-4 ppm cross-checked on two
stations.
New tools/infrastructure (kept, not one-off):
- Si4684Driver::recalibrateXtal() + POST /api/tuner/xtal-calibrate:
live crystal re-trim without an ESP32 reflash.
- FM_RSQ FREQOFF exposed as "freqoff_ppm" in GET /api/tuner/status.
- tools/si4684_xtal_calibration.py: automates the trim loop.
- tools/si4684_antenna_calibration.py: AN851 Appendix A ANTCAP/VARM/VARB
sweep tool (same session, separate calibration).
- CONFIG_ESP32_I2S_TEST_TONE (off by default): isolates Si4684-specific
audio issues from shared-downstream ones by writing a tone directly
over the I2S bus the Si4684 also uses.
- SIGMA_WRITE_REGISTER_BLOCK/sigma_safeload_block now retry on NACK and
verify via read-back instead of firing I2C writes blind.
- FM de-emphasis set to European 50us (was left at the US 75us default).
- DAB_ACF_ENABLE restored to its previous 0x0000 with a citation
explaining why (tested the datasheet default of 0x0003, made things
audibly worse).
See docs/si4684-rf-investigation-report.md's 2026-08-23 entry for the
full elimination chain and docs/TODO.md for follow-up work (persisting
calibration results to EEPROM instead of requiring a firmware edit).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Extend the FM-only ANTCAP antenna-varactor override to DAB, mirroring the
existing mechanism end to end (driver, tuner, service, EEPROM storage,
HTTP API). Live sweep on real hardware found no ANTCAP value beating
auto-tune on the ensembles tested, so DAB stays on auto-tune by default.
Also fix BT1035 boot: the module's real boot banner doesn't appear until
~18-24s after RESET# releases, not the 3.5s previously waited; add a
2-attempt retry and a baud-rate probe fallback for diagnostics.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
micheleandClaude Sonnet 5