micheleandClaude Sonnet 5
fae2305164
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>
58 lines
1.5 KiB
C++
58 lines
1.5 KiB
C++
/**
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* @file esp32_i2s_test_tone.cpp
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* @brief esp32_i2s_test_tone implementation.
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*
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* DigiRadio firmware — https://github.com/manvalan/DigiRadio
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*
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* Copyright 2026 Michele Bigi
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include "esp32_i2s_test_tone.hpp"
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#include "esp32_i2s_sink.hpp"
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#include <cmath>
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#include <cstdint>
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#include <numbers>
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namespace esp32_i2s_test_tone {
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namespace {
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constexpr int kSampleRateHz = 48000;
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constexpr int kFramesPerBlock = 256;
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/** writeSamples() wants top-aligned 24-bit in a 32-bit slot -- 8-bit shift. */
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constexpr int kTopAlignShift = 8;
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/** Modest amplitude: audible but not a full-scale blast. */
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constexpr float kAmplitude = 0.4F * 8388607.0F;
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constexpr float kTwoPi = 2.0F * std::numbers::pi_v<float>;
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} // namespace
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[[noreturn]] void run(float freqHz)
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{
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esp32_i2s_sink::tryAcquire();
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const float phaseStep = kTwoPi * freqHz / static_cast<float>(kSampleRateHz);
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float phase = 0.0F;
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std::int32_t buf[kFramesPerBlock * 2];
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for (;;)
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{
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for (int i = 0; i < kFramesPerBlock; ++i)
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{
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phase += phaseStep;
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if (phase > kTwoPi)
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{
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phase -= kTwoPi;
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}
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const auto sample =
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static_cast<std::int32_t>(std::sin(phase) * kAmplitude)
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<< kTopAlignShift;
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buf[(i * 2) + 0] = sample;
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buf[(i * 2) + 1] = sample;
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}
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esp32_i2s_sink::writeSamples(buf, kFramesPerBlock * 2);
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}
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}
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} // namespace esp32_i2s_test_tone
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