Safety, testing Exercise 21 README internal linking on Forgejo

2026-04-14 11:16:54 -07:00 · 2026-04-14 11:16:54 -07:00 · 1d0a29f2a3
commit 1d0a29f2a3
parent e5d30469bc
18 changed files with 2098 additions and 1 deletions
--- a/exercises/20_microphone/README.md
+++ b/exercises/20_microphone/README.md
@ -0,0 +1,3 @@
+https://github.com/Xinyuan-LilyGO/LilyGo-LoRa-Series/issues/295#issuecomment-4241577603
+
+tells us that the Specification as of April13, 2026, incorrectly includes a microphone.  There is no microphone.  The code here was ChatGPT's Codex trying to find the correct pins, a task that could never be accomplished.  This exercise documents the attempts for posterity.
--- a/exercises/20_microphone/lib/mic_recorder/MicrophoneRecorder.cpp
+++ b/exercises/20_microphone/lib/mic_recorder/MicrophoneRecorder.cpp
@ -0,0 +1,453 @@
+#include "MicrophoneRecorder.h"
+
+#include <SPI.h>
+#include <Wire.h>
+#include <driver/i2s.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <time.h>
+
+#include "driver/gpio.h"
+#include "tbeam_supreme_adapter.h"
+
+#ifndef MIC_SAMPLE_RATE
+#define MIC_SAMPLE_RATE 16000
+#endif
+
+#ifndef MIC_BITS_PER_SAMPLE
+#define MIC_BITS_PER_SAMPLE 16
+#endif
+
+#ifndef MIC_DATA_PIN
+#define MIC_DATA_PIN 38
+#endif
+
+#ifndef MIC_CLK_PIN
+#define MIC_CLK_PIN 39
+#endif
+
+#ifndef MIC_SELECT_PIN
+#define MIC_SELECT_PIN 48
+#endif
+
+#ifndef MIC_SELECT_LEFT
+#define MIC_SELECT_LEFT 1
+#endif
+
+#ifndef FW_BUILD_EPOCH
+#define FW_BUILD_EPOCH 0
+#endif
+
+namespace {
+
+constexpr i2s_port_t kI2sPort = I2S_NUM_0;
+constexpr uint32_t kChunkBytes = 2048;
+constexpr uint8_t kWavChannels = 1;
+constexpr uint32_t kValidEpochFloor = 1700000000UL;
+
+}  // namespace
+
+MicrophoneRecorder::MicrophoneRecorder(Print& out) : out_(out) {}
+
+MicrophoneRecorder::~MicrophoneRecorder() {
+  close();
+  deactivateMicrophone();
+}
+
+bool MicrophoneRecorder::begin() {
+  micCfg_ = {
+      .dataPin = MIC_DATA_PIN,
+      .clkPin = MIC_CLK_PIN,
+      .selectPin = MIC_SELECT_PIN,
+      .selectLeft = (MIC_SELECT_LEFT != 0),
+  };
+
+  forceSpiDeselected();
+  pmuReady_ = initPmu();
+  if (!pmuReady_) {
+    return false;
+  }
+
+  cycleSdRail();
+  sdReady_ = mountSdCard();
+  if (!sdReady_) {
+    logf("SD mount failed");
+    return false;
+  }
+
+  if (!ensureDirectory("/recordings")) {
+    logf("failed to create /recordings");
+    return false;
+  }
+
+  logf("ready: sample_rate=%u bits=%u data=%d clk=%d sel=%d",
+       (unsigned)MIC_SAMPLE_RATE,
+       (unsigned)MIC_BITS_PER_SAMPLE,
+       micCfg_.dataPin,
+       micCfg_.clkPin,
+       micCfg_.selectPin);
+  return true;
+}
+
+void MicrophoneRecorder::setRuntimeConfig(const MicRuntimeConfig& cfg) {
+  deactivateMicrophone();
+  micCfg_ = cfg;
+  logf("config updated: data=%d clk=%d select=%d left=%d",
+       micCfg_.dataPin,
+       micCfg_.clkPin,
+       micCfg_.selectPin,
+       micCfg_.selectLeft ? 1 : 0);
+}
+
+bool MicrophoneRecorder::activateMicrophone() {
+  if (micActive_) {
+    return true;
+  }
+
+  pinMode(micCfg_.selectPin, OUTPUT);
+  digitalWrite(micCfg_.selectPin, micCfg_.selectLeft ? LOW : HIGH);
+
+  const i2s_config_t config = {
+      .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX | I2S_MODE_PDM),
+      .sample_rate = MIC_SAMPLE_RATE,
+      .bits_per_sample = (i2s_bits_per_sample_t)MIC_BITS_PER_SAMPLE,
+      .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
+      .communication_format = I2S_COMM_FORMAT_STAND_I2S,
+      .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
+      .dma_buf_count = 8,
+      .dma_buf_len = 256,
+      .use_apll = false,
+      .tx_desc_auto_clear = false,
+      .fixed_mclk = 0,
+#if ESP_IDF_VERSION_MAJOR >= 4
+      .mclk_multiple = I2S_MCLK_MULTIPLE_DEFAULT,
+      .bits_per_chan = I2S_BITS_PER_CHAN_DEFAULT,
+#endif
+  };
+
+  const i2s_pin_config_t pins = {
+      .bck_io_num = I2S_PIN_NO_CHANGE,
+      .ws_io_num = micCfg_.clkPin,
+      .data_out_num = I2S_PIN_NO_CHANGE,
+      .data_in_num = micCfg_.dataPin,
+  };
+
+  i2s_driver_uninstall(kI2sPort);
+  esp_err_t err = i2s_driver_install(kI2sPort, &config, 0, nullptr);
+  if (err != ESP_OK) {
+    logf("i2s_driver_install failed err=%d", (int)err);
+    return false;
+  }
+
+  err = i2s_set_pin(kI2sPort, &pins);
+  if (err != ESP_OK) {
+    logf("i2s_set_pin failed err=%d", (int)err);
+    i2s_driver_uninstall(kI2sPort);
+    return false;
+  }
+
+  err = i2s_set_pdm_rx_down_sample(kI2sPort, I2S_PDM_DSR_8S);
+  if (err != ESP_OK) {
+    logf("i2s_set_pdm_rx_down_sample failed err=%d", (int)err);
+    i2s_driver_uninstall(kI2sPort);
+    return false;
+  }
+
+  i2s_zero_dma_buffer(kI2sPort);
+  micActive_ = true;
+  logf("microphone active clk(ws)=%d data=%d select=%d left=%d",
+       micCfg_.clkPin,
+       micCfg_.dataPin,
+       micCfg_.selectPin,
+       micCfg_.selectLeft ? 1 : 0);
+  return true;
+}
+
+void MicrophoneRecorder::deactivateMicrophone() {
+  if (!micActive_) {
+    return;
+  }
+
+  i2s_driver_uninstall(kI2sPort);
+  micActive_ = false;
+  logf("microphone inactive");
+}
+
+bool MicrophoneRecorder::open(const char* path) {
+  if (!sdReady_) {
+    logf("open refused: SD not ready");
+    return false;
+  }
+
+  close();
+
+  strncpy(currentPath_, path, sizeof(currentPath_) - 1);
+  currentPath_[sizeof(currentPath_) - 1] = '\0';
+
+  file_ = SD.open(currentPath_, FILE_WRITE);
+  if (!file_) {
+    logf("failed to open %s", currentPath_);
+    currentPath_[0] = '\0';
+    return false;
+  }
+
+  wavDataBytes_ = 0;
+  fileOpen_ = writeWavHeader();
+  if (!fileOpen_) {
+    file_.close();
+    currentPath_[0] = '\0';
+    return false;
+  }
+
+  logf("opened %s", currentPath_);
+  return true;
+}
+
+bool MicrophoneRecorder::openTimestamped() {
+  const uint32_t stamp = selectTimestamp();
+  char path[96];
+  snprintf(path, sizeof(path), "/recordings/mic_%lu.wav", (unsigned long)stamp);
+  return open(path);
+}
+
+bool MicrophoneRecorder::captureForMs(uint32_t durationMs) {
+  if (!fileOpen_) {
+    logf("capture refused: no open file");
+    return false;
+  }
+  if (!activateMicrophone()) {
+    return false;
+  }
+
+  int16_t samples[kChunkBytes / sizeof(int16_t)];
+  const uint32_t startMs = millis();
+  uint32_t lastProgressMs = startMs;
+  int16_t secondMin = INT16_MAX;
+  int16_t secondMax = INT16_MIN;
+  uint32_t secondSampleCount = 0;
+  uint64_t secondAbsSum = 0;
+
+  while ((uint32_t)(millis() - startMs) < durationMs) {
+    size_t bytesRead = 0;
+    const esp_err_t err =
+        i2s_read(kI2sPort, samples, sizeof(samples), &bytesRead, pdMS_TO_TICKS(250));
+    if (err != ESP_OK) {
+      logf("i2s_read failed err=%d", (int)err);
+      return false;
+    }
+
+    if (bytesRead > 0) {
+      const size_t sampleCount = bytesRead / sizeof(samples[0]);
+      for (size_t i = 0; i < sampleCount; ++i) {
+        const int16_t value = samples[i];
+        if (value < secondMin) secondMin = value;
+        if (value > secondMax) secondMax = value;
+        secondAbsSum += (uint64_t)(value < 0 ? -(int32_t)value : value);
+      }
+      secondSampleCount += sampleCount;
+
+      const size_t wrote = file_.write((const uint8_t*)samples, bytesRead);
+      if (wrote != bytesRead) {
+        logf("file write failed wanted=%u wrote=%u", (unsigned)bytesRead, (unsigned)wrote);
+        return false;
+      }
+      wavDataBytes_ += wrote;
+    }
+
+    const uint32_t now = millis();
+    if ((uint32_t)(now - lastProgressMs) >= 1000) {
+      lastProgressMs = now;
+      const unsigned long avgAbs =
+          secondSampleCount > 0 ? (unsigned long)(secondAbsSum / secondSampleCount) : 0UL;
+      const char* status =
+          (secondSampleCount == 0) ? "nosamples"
+          : (secondMin == secondMax) ? "flat"
+          : (avgAbs < 8UL) ? "nearzero"
+          : "active";
+      logf("recording %s elapsed=%lus bytes=%lu min=%d max=%d avgabs=%lu samples=%lu status=%s",
+           currentPath_,
+           (unsigned long)((now - startMs) / 1000),
+           (unsigned long)wavDataBytes_,
+           secondSampleCount > 0 ? secondMin : 0,
+           secondSampleCount > 0 ? secondMax : 0,
+           avgAbs,
+           (unsigned long)secondSampleCount,
+           status);
+      secondMin = INT16_MAX;
+      secondMax = INT16_MIN;
+      secondSampleCount = 0;
+      secondAbsSum = 0;
+    }
+  }
+
+  file_.flush();
+  return true;
+}
+
+void MicrophoneRecorder::close() {
+  if (!fileOpen_) {
+    return;
+  }
+
+  finalizeWavHeader();
+  file_.close();
+  fileOpen_ = false;
+  logf("closed %s bytes=%lu", currentPath_, (unsigned long)wavDataBytes_);
+  currentPath_[0] = '\0';
+}
+
+void MicrophoneRecorder::logf(const char* fmt, ...) {
+  char msg[200];
+  va_list args;
+  va_start(args, fmt);
+  vsnprintf(msg, sizeof(msg), fmt, args);
+  va_end(args);
+
+  out_.printf("[%10lu][%06lu] %s\r\n",
+              (unsigned long)millis(),
+              (unsigned long)logSeq_++,
+              msg);
+}
+
+bool MicrophoneRecorder::initPmu() {
+  if (!tbeam_supreme::initPmuForPeripherals(pmu_, &out_)) {
+    logf("PMU init failed");
+    return false;
+  }
+  return true;
+}
+
+void MicrophoneRecorder::forceSpiDeselected() {
+  pinMode(tbeam_supreme::sdCs(), OUTPUT);
+  digitalWrite(tbeam_supreme::sdCs(), HIGH);
+  pinMode(tbeam_supreme::imuCs(), OUTPUT);
+  digitalWrite(tbeam_supreme::imuCs(), HIGH);
+}
+
+void MicrophoneRecorder::cycleSdRail(uint32_t offMs, uint32_t onSettleMs) {
+  if (!pmu_) {
+    return;
+  }
+
+  forceSpiDeselected();
+  SD.end();
+  sdSpiH_.end();
+  sdSpiF_.end();
+
+  pmu_->disablePowerOutput(XPOWERS_BLDO1);
+  delay(offMs);
+  pmu_->setPowerChannelVoltage(XPOWERS_BLDO1, 3300);
+  pmu_->enablePowerOutput(XPOWERS_BLDO1);
+  delay(onSettleMs);
+}
+
+bool MicrophoneRecorder::mountSdCard() {
+  const uint32_t freqs[] = {400000, 1000000, 4000000, 10000000};
+
+  for (uint8_t i = 0; i < (sizeof(freqs) / sizeof(freqs[0])); ++i) {
+    if (tryMountWithBus(sdSpiH_, "HSPI", freqs[i])) {
+      return true;
+    }
+  }
+  for (uint8_t i = 0; i < (sizeof(freqs) / sizeof(freqs[0])); ++i) {
+    if (tryMountWithBus(sdSpiF_, "FSPI", freqs[i])) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool MicrophoneRecorder::tryMountWithBus(SPIClass& bus, const char* busName, uint32_t hz) {
+  SD.end();
+  bus.end();
+  delay(5);
+  forceSpiDeselected();
+
+  bus.begin(tbeam_supreme::sdSck(),
+            tbeam_supreme::sdMiso(),
+            tbeam_supreme::sdMosi(),
+            tbeam_supreme::sdCs());
+  digitalWrite(tbeam_supreme::sdCs(), HIGH);
+  delay(1);
+  for (uint8_t i = 0; i < 10; ++i) {
+    bus.transfer(0xFF);
+  }
+
+  if (!SD.begin(tbeam_supreme::sdCs(), bus, hz)) {
+    return false;
+  }
+  if (SD.cardType() == CARD_NONE) {
+    SD.end();
+    return false;
+  }
+
+  activeSdSpi_ = &bus;
+  logf("SD mounted via %s @ %lu Hz", busName, (unsigned long)hz);
+  return true;
+}
+
+bool MicrophoneRecorder::ensureDirectory(const char* path) {
+  if (SD.exists(path)) {
+    return true;
+  }
+  return SD.mkdir(path);
+}
+
+bool MicrophoneRecorder::writeWavHeader() {
+  const WavHeader header = {
+      .riff = {'R', 'I', 'F', 'F'},
+      .chunkSize = 36,
+      .wave = {'W', 'A', 'V', 'E'},
+      .fmt = {'f', 'm', 't', ' '},
+      .subchunk1Size = 16,
+      .audioFormat = 1,
+      .numChannels = kWavChannels,
+      .sampleRate = MIC_SAMPLE_RATE,
+      .byteRate = MIC_SAMPLE_RATE * kWavChannels * (MIC_BITS_PER_SAMPLE / 8),
+      .blockAlign = (uint16_t)(kWavChannels * (MIC_BITS_PER_SAMPLE / 8)),
+      .bitsPerSample = MIC_BITS_PER_SAMPLE,
+      .data = {'d', 'a', 't', 'a'},
+      .dataSize = 0,
+  };
+
+  return file_.write((const uint8_t*)&header, sizeof(header)) == sizeof(header);
+}
+
+bool MicrophoneRecorder::finalizeWavHeader() {
+  if (!file_) {
+    return false;
+  }
+
+  WavHeader header = {
+      .riff = {'R', 'I', 'F', 'F'},
+      .chunkSize = 36 + wavDataBytes_,
+      .wave = {'W', 'A', 'V', 'E'},
+      .fmt = {'f', 'm', 't', ' '},
+      .subchunk1Size = 16,
+      .audioFormat = 1,
+      .numChannels = kWavChannels,
+      .sampleRate = MIC_SAMPLE_RATE,
+      .byteRate = MIC_SAMPLE_RATE * kWavChannels * (MIC_BITS_PER_SAMPLE / 8),
+      .blockAlign = (uint16_t)(kWavChannels * (MIC_BITS_PER_SAMPLE / 8)),
+      .bitsPerSample = MIC_BITS_PER_SAMPLE,
+      .data = {'d', 'a', 't', 'a'},
+      .dataSize = wavDataBytes_,
+  };
+
+  file_.seek(0);
+  const bool ok = file_.write((const uint8_t*)&header, sizeof(header)) == sizeof(header);
+  file_.seek(file_.size());
+  return ok;
+}
+
+uint32_t MicrophoneRecorder::selectTimestamp() const {
+  const time_t now = time(nullptr);
+  if (now >= (time_t)kValidEpochFloor) {
+    return (uint32_t)now;
+  }
+  if (FW_BUILD_EPOCH >= kValidEpochFloor) {
+    return (uint32_t)FW_BUILD_EPOCH + (millis() / 1000UL);
+  }
+  return millis() / 1000UL;
+}
--- a/exercises/20_microphone/lib/mic_recorder/MicrophoneRecorder.h
+++ b/exercises/20_microphone/lib/mic_recorder/MicrophoneRecorder.h
@ -0,0 +1,78 @@
+#pragma once
+
+#include <Arduino.h>
+#include <SD.h>
+#include <SPI.h>
+#include <XPowersLib.h>
+
+class MicrophoneRecorder {
+ public:
+  struct MicRuntimeConfig {
+    int dataPin;
+    int clkPin;
+    int selectPin;
+    bool selectLeft;
+  };
+
+  explicit MicrophoneRecorder(Print& out = Serial);
+  ~MicrophoneRecorder();
+
+  bool begin();
+  void setRuntimeConfig(const MicRuntimeConfig& cfg);
+  const MicRuntimeConfig& runtimeConfig() const { return micCfg_; }
+  bool activateMicrophone();
+  void deactivateMicrophone();
+
+  bool open(const char* path);
+  bool openTimestamped();
+  bool captureForMs(uint32_t durationMs);
+  void close();
+
+  bool isSdReady() const { return sdReady_; }
+  bool isMicActive() const { return micActive_; }
+  bool isOpen() const { return fileOpen_; }
+  const char* currentPath() const { return currentPath_; }
+
+ private:
+  struct WavHeader {
+    char riff[4];
+    uint32_t chunkSize;
+    char wave[4];
+    char fmt[4];
+    uint32_t subchunk1Size;
+    uint16_t audioFormat;
+    uint16_t numChannels;
+    uint32_t sampleRate;
+    uint32_t byteRate;
+    uint16_t blockAlign;
+    uint16_t bitsPerSample;
+    char data[4];
+    uint32_t dataSize;
+  };
+
+  void logf(const char* fmt, ...);
+  bool initPmu();
+  void forceSpiDeselected();
+  void cycleSdRail(uint32_t offMs = 250, uint32_t onSettleMs = 700);
+  bool mountSdCard();
+  bool tryMountWithBus(SPIClass& bus, const char* busName, uint32_t hz);
+  bool ensureDirectory(const char* path);
+  bool writeWavHeader();
+  bool finalizeWavHeader();
+  uint32_t selectTimestamp() const;
+
+  Print& out_;
+  SPIClass sdSpiH_{HSPI};
+  SPIClass sdSpiF_{FSPI};
+  SPIClass* activeSdSpi_ = nullptr;
+  XPowersLibInterface* pmu_ = nullptr;
+  File file_;
+  char currentPath_[96] = {0};
+  uint32_t logSeq_ = 0;
+  uint32_t wavDataBytes_ = 0;
+  bool pmuReady_ = false;
+  bool sdReady_ = false;
+  bool micActive_ = false;
+  bool fileOpen_ = false;
+  MicRuntimeConfig micCfg_{};
+};
--- a/exercises/20_microphone/lib/mic_recorder/library.json
+++ b/exercises/20_microphone/lib/mic_recorder/library.json
@ -0,0 +1,7 @@
+{
+  "name": "mic_recorder",
+  "version": "0.1.0",
+  "build": {
+    "includeDir": "."
+  }
+}
--- a/exercises/20_microphone/platformio.ini
+++ b/exercises/20_microphone/platformio.ini
@ -0,0 +1,81 @@
+; 20260413 ChatGPT
+; Exercise 20_microphone
+
+[platformio]
+default_envs = guy
+
+[env]
+platform = espressif32
+framework = arduino
+board = esp32-s3-devkitc-1
+board_build.partitions = default_8MB.csv
+monitor_speed = 115200
+extra_scripts = pre:scripts/set_build_epoch.py
+lib_deps =
+  Wire
+  olikraus/U8g2@^2.36.4
+  lewisxhe/XPowersLib@0.3.3
+
+build_flags =
+  -I ../../shared/boards
+  -I ../../external/microReticulum_Firmware
+  -D BOARD_MODEL=BOARD_TBEAM_S_V1
+  -D ARDUINO_USB_MODE=1
+  -D ARDUINO_USB_CDC_ON_BOOT=1
+  -D MIC_SAMPLE_RATE=16000
+  -D MIC_BITS_PER_SAMPLE=16
+  -D MIC_RECORD_SECONDS=30
+  -D MIC_IDLE_SECONDS=30
+  -D MIC_DATA_PIN=39
+  -D MIC_CLK_PIN=38
+  -D MIC_SELECT_PIN=48
+  -D MIC_SELECT_LEFT=1
+
+[env:amy]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D BOARD_ID=\"AMY\"
+  -D NODE_LABEL=\"Amy\"
+
+[env:bob]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D BOARD_ID=\"BOB\"
+  -D NODE_LABEL=\"Bob\"
+
+[env:cy]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D BOARD_ID=\"CY\"
+  -D NODE_LABEL=\"Cy\"
+
+[env:dan]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D BOARD_ID=\"DAN\"
+  -D NODE_LABEL=\"Dan\"
+
+[env:ed]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D BOARD_ID=\"ED\"
+  -D NODE_LABEL=\"Ed\"
+
+[env:flo]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D BOARD_ID=\"FLO\"
+  -D NODE_LABEL=\"Flo\"
+
+[env:guy]
+extends = env
+build_flags =
+  ${env.build_flags}
+  -D BOARD_ID=\"GUY\"
+  -D NODE_LABEL=\"Guy\"
--- a/exercises/20_microphone/scripts/set_build_epoch.py
+++ b/exercises/20_microphone/scripts/set_build_epoch.py
@ -0,0 +1,13 @@
+import time
+Import("env")
+
+epoch = int(time.time())
+utc_tag = time.strftime("%Y%m%d_%H%M%S_z", time.gmtime(epoch))
+
+env.Append(
+    CPPDEFINES=[
+        ("FW_BUILD_EPOCH", str(epoch)),
+        ("FW_BUILD_UTC", '\"%s\"' % utc_tag),
+    ]
+)
+
--- a/exercises/20_microphone/src/main.cpp
+++ b/exercises/20_microphone/src/main.cpp
@ -0,0 +1,137 @@
+// 20260413 ChatGPT
+// Exercise 20: microphone recorder
+
+#include <Arduino.h>
+
+#include "MicrophoneRecorder.h"
+
+#ifndef NODE_LABEL
+#define NODE_LABEL "MIC"
+#endif
+
+#ifndef MIC_RECORD_SECONDS
+#define MIC_RECORD_SECONDS 30
+#endif
+
+#ifndef MIC_IDLE_SECONDS
+#define MIC_IDLE_SECONDS 30
+#endif
+
+#ifndef MIC_STARTUP_WAIT_SECONDS
+#define MIC_STARTUP_WAIT_SECONDS 10
+#endif
+
+namespace {
+
+constexpr uint32_t kSerialDelayMs = 1500;
+constexpr uint32_t kBetweenRecordingsMs = MIC_IDLE_SECONDS * 1000UL;
+
+MicrophoneRecorder g_recorder(Serial);
+bool g_started = false;
+bool g_finished = false;
+size_t g_caseIndex = 0;
+uint32_t g_nextActionMs = 0;
+
+struct SweepCase {
+  const char* label;
+  MicrophoneRecorder::MicRuntimeConfig cfg;
+};
+
+SweepCase g_cases[] = {
+    {"base", {.dataPin = MIC_DATA_PIN, .clkPin = MIC_CLK_PIN, .selectPin = MIC_SELECT_PIN, .selectLeft = (MIC_SELECT_LEFT != 0)}},
+    {"flip_lr", {.dataPin = MIC_DATA_PIN, .clkPin = MIC_CLK_PIN, .selectPin = MIC_SELECT_PIN, .selectLeft = (MIC_SELECT_LEFT == 0)}},
+    {"swap_pins", {.dataPin = MIC_CLK_PIN, .clkPin = MIC_DATA_PIN, .selectPin = MIC_SELECT_PIN, .selectLeft = (MIC_SELECT_LEFT != 0)}},
+    {"swap_flip", {.dataPin = MIC_CLK_PIN, .clkPin = MIC_DATA_PIN, .selectPin = MIC_SELECT_PIN, .selectLeft = (MIC_SELECT_LEFT == 0)}},
+};
+
+void printWhatToSay(const SweepCase& sweepCase) {
+  Serial.println();
+  Serial.println("Speak this sentence clearly 3 times during the test:");
+  Serial.println("\"Testing T-Beam microphone case "
+                 + String(sweepCase.label)
+                 + ". One two three four five.\"");
+  Serial.println("Look for console lines where:");
+  Serial.println("  status=active");
+  Serial.println("  min and max change over time and are not equal");
+  Serial.println("  avgabs is not stuck at one repeated value");
+  Serial.println("If status=flat with min=max every second, that case is bad.");
+}
+
+}  // namespace
+
+void setup() {
+  Serial.begin(115200);
+  delay(kSerialDelayMs);
+
+  Serial.println();
+  Serial.println("============================================================");
+  Serial.printf("Exercise 20 Microphone Recorder [%s]\r\n", NODE_LABEL);
+  Serial.println("============================================================");
+
+  if (!g_recorder.begin()) {
+    Serial.println("Recorder init failed; loop will retry.");
+  }
+
+  Serial.printf("Waiting %u seconds before the first recording.\r\n",
+                (unsigned)MIC_STARTUP_WAIT_SECONDS);
+  g_nextActionMs = millis() + MIC_STARTUP_WAIT_SECONDS * 1000UL;
+}
+
+void loop() {
+  if (!g_recorder.isSdReady() || g_finished) {
+    delay(1000);
+    return;
+  }
+
+  const uint32_t now = millis();
+  if ((int32_t)(now - g_nextActionMs) < 0) {
+    delay(100);
+    return;
+  }
+
+  if (g_caseIndex >= (sizeof(g_cases) / sizeof(g_cases[0]))) {
+    Serial.println("Microphone sweep complete. No more recordings will be started.");
+    g_finished = true;
+    return;
+  }
+
+  SweepCase& sweepCase = g_cases[g_caseIndex];
+  g_recorder.setRuntimeConfig(sweepCase.cfg);
+
+  char path[96];
+  snprintf(path,
+           sizeof(path),
+           "/recordings/mic_%s_%lu.wav",
+           sweepCase.label,
+           (unsigned long)time(nullptr));
+
+  Serial.println();
+  Serial.printf("Starting case %u/%u: %s data=%d clk=%d select=%d left=%d\r\n",
+                (unsigned)(g_caseIndex + 1),
+                (unsigned)(sizeof(g_cases) / sizeof(g_cases[0])),
+                sweepCase.label,
+                sweepCase.cfg.dataPin,
+                sweepCase.cfg.clkPin,
+                sweepCase.cfg.selectPin,
+                sweepCase.cfg.selectLeft ? 1 : 0);
+  printWhatToSay(sweepCase);
+
+  if (!g_recorder.open(path)) {
+    Serial.println("Failed to open output file; delaying and retrying.");
+    g_nextActionMs = millis() + 1000;
+    delay(100);
+    return;
+  }
+
+  const bool ok = g_recorder.captureForMs(MIC_RECORD_SECONDS * 1000UL);
+  g_recorder.close();
+
+  Serial.printf("case %s status=%s next_case_in=%lus\r\n",
+                sweepCase.label,
+                ok ? "ok" : "failed",
+                (unsigned long)(kBetweenRecordingsMs / 1000UL));
+
+  g_caseIndex++;
+  g_nextActionMs = millis() + kBetweenRecordingsMs;
+  delay(100);
+}
--- a/exercises/20_microphone/trial_1_console.log
+++ b/exercises/20_microphone/trial_1_console.log
@ -0,0 +1,172 @@
+(rnsenv) jlpoole@jp ~/workstation $ date; pio device monitor -b 115200 --port /dev/ttytCY
+Mon Apr 13 20:32:15 PDT 2026
+/home/jlpoole/rnsenv/lib/python3.13/site-packages/requests/__init__.py:113: RequestsDependencyWarning: urllib3 (2.6.1) or chardet (6.0.0.post1)/charset_normalizer (3.4.4) doesn't match a supported version!
+  warnings.warn(
+--- Terminal on /dev/ttytCY | 115200 8-N-1
+--- Available filters and text transformations: colorize, debug, default, direct, hexlify, log2file, nocontrol, printable, send_on_enter, time
+--- More details at https://bit.ly/pio-monitor-filters
+--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H
+[     13073][000002] config updated: data=39 clk=38 select=48 left=1
+
+Starting case 1/4: base data=39 clk=38 select=48 left=1
+
+Speak this sentence clearly 3 times during the test:
+"Testing T-Beam microphone case base. One two three four five."
+Look for console lines where:
+  status=active
+  min and max change over time and are not equal
+  avgabs is not stuck at one repeated value
+If status=flat with min=max every second, that case is bad.
+[     13152][000003] opened /recordings/mic_base_19.wav
+E (13037) I2S: i2s_driver_uninstall(2048): I2S port 0 has not installed
+[     13153][000004] microphone active clk(ws)=38 data=39 select=48 left=1
+[     14158][000005] recording /recordings/mic_base_19.wav elapsed=1s bytes=30720 min=-31424 max=41 avgabs=30930 samples=15360 status=active
+[     15182][000006] recording /recordings/mic_base_19.wav elapsed=2s bytes=63488 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     16206][000007] recording /recordings/mic_base_19.wav elapsed=3s bytes=96256 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     17230][000008] recording /recordings/mic_base_19.wav elapsed=4s bytes=129024 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     18254][000009] recording /recordings/mic_base_19.wav elapsed=5s bytes=161792 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     19278][000010] recording /recordings/mic_base_19.wav elapsed=6s bytes=194560 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     20302][000011] recording /recordings/mic_base_19.wav elapsed=7s bytes=227328 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     21326][000012] recording /recordings/mic_base_19.wav elapsed=8s bytes=260096 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     22350][000013] recording /recordings/mic_base_19.wav elapsed=9s bytes=292864 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     23374][000014] recording /recordings/mic_base_19.wav elapsed=10s bytes=325632 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     24398][000015] recording /recordings/mic_base_19.wav elapsed=11s bytes=358400 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     25422][000016] recording /recordings/mic_base_19.wav elapsed=12s bytes=391168 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     26446][000017] recording /recordings/mic_base_19.wav elapsed=13s bytes=423936 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     27470][000018] recording /recordings/mic_base_19.wav elapsed=14s bytes=456704 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     28494][000019] recording /recordings/mic_base_19.wav elapsed=15s bytes=489472 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     29518][000020] recording /recordings/mic_base_19.wav elapsed=16s bytes=522240 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     30542][000021] recording /recordings/mic_base_19.wav elapsed=17s bytes=555008 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     31566][000022] recording /recordings/mic_base_19.wav elapsed=18s bytes=587776 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     32590][000023] recording /recordings/mic_base_19.wav elapsed=19s bytes=620544 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     33614][000024] recording /recordings/mic_base_19.wav elapsed=20s bytes=653312 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     34638][000025] recording /recordings/mic_base_19.wav elapsed=21s bytes=686080 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     35662][000026] recording /recordings/mic_base_19.wav elapsed=22s bytes=718848 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     36686][000027] recording /recordings/mic_base_19.wav elapsed=23s bytes=751616 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     37710][000028] recording /recordings/mic_base_19.wav elapsed=24s bytes=784384 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     38734][000029] recording /recordings/mic_base_19.wav elapsed=25s bytes=817152 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     39758][000030] recording /recordings/mic_base_19.wav elapsed=26s bytes=849920 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     40782][000031] recording /recordings/mic_base_19.wav elapsed=27s bytes=882688 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     41806][000032] recording /recordings/mic_base_19.wav elapsed=28s bytes=915456 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     42830][000033] recording /recordings/mic_base_19.wav elapsed=29s bytes=948224 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     43375][000034] closed /recordings/mic_base_19.wav bytes=960512
+case base status=ok next_case_in=30s
+[     73375][000035] microphone inactive
+[     73376][000036] config updated: data=39 clk=38 select=48 left=0
+
+Starting case 2/4: flip_lr data=39 clk=38 select=48 left=0
+
+Speak this sentence clearly 3 times during the test:
+"Testing T-Beam microphone case flip_lr. One two three four five."
+Look for console lines where:
+  status=active
+  min and max change over time and are not equal
+  avgabs is not stuck at one repeated value
+If status=flat with min=max every second, that case is bad.
+[     73465][000037] opened /recordings/mic_flip_lr_79.wav
+E (73350) I2S: i2s_driver_uninstall(2048): I2S port 0 has not installed
+[     73466][000038] microphone active clk(ws)=38 data=39 select=48 left=0
+[     74471][000039] recording /recordings/mic_flip_lr_79.wav elapsed=1s bytes=30720 min=-32768 max=25661 avgabs=30858 samples=15360 status=active
+[     75495][000040] recording /recordings/mic_flip_lr_79.wav elapsed=2s bytes=63488 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     76519][000041] recording /recordings/mic_flip_lr_79.wav elapsed=3s bytes=96256 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     77543][000042] recording /recordings/mic_flip_lr_79.wav elapsed=4s bytes=129024 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     78567][000043] recording /recordings/mic_flip_lr_79.wav elapsed=5s bytes=161792 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     79591][000044] recording /recordings/mic_flip_lr_79.wav elapsed=6s bytes=194560 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     80615][000045] recording /recordings/mic_flip_lr_79.wav elapsed=7s bytes=227328 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     81639][000046] recording /recordings/mic_flip_lr_79.wav elapsed=8s bytes=260096 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     82663][000047] recording /recordings/mic_flip_lr_79.wav elapsed=9s bytes=292864 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     83687][000048] recording /recordings/mic_flip_lr_79.wav elapsed=10s bytes=325632 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     84711][000049] recording /recordings/mic_flip_lr_79.wav elapsed=11s bytes=358400 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     85735][000050] recording /recordings/mic_flip_lr_79.wav elapsed=12s bytes=391168 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     86759][000051] recording /recordings/mic_flip_lr_79.wav elapsed=13s bytes=423936 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     87783][000052] recording /recordings/mic_flip_lr_79.wav elapsed=14s bytes=456704 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     88807][000053] recording /recordings/mic_flip_lr_79.wav elapsed=15s bytes=489472 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     89831][000054] recording /recordings/mic_flip_lr_79.wav elapsed=16s bytes=522240 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     90855][000055] recording /recordings/mic_flip_lr_79.wav elapsed=17s bytes=555008 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     91879][000056] recording /recordings/mic_flip_lr_79.wav elapsed=18s bytes=587776 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     92903][000057] recording /recordings/mic_flip_lr_79.wav elapsed=19s bytes=620544 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     93927][000058] recording /recordings/mic_flip_lr_79.wav elapsed=20s bytes=653312 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     94951][000059] recording /recordings/mic_flip_lr_79.wav elapsed=21s bytes=686080 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     95975][000060] recording /recordings/mic_flip_lr_79.wav elapsed=22s bytes=718848 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     96999][000061] recording /recordings/mic_flip_lr_79.wav elapsed=23s bytes=751616 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     98023][000062] recording /recordings/mic_flip_lr_79.wav elapsed=24s bytes=784384 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[     99047][000063] recording /recordings/mic_flip_lr_79.wav elapsed=25s bytes=817152 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    100071][000064] recording /recordings/mic_flip_lr_79.wav elapsed=26s bytes=849920 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    101095][000065] recording /recordings/mic_flip_lr_79.wav elapsed=27s bytes=882688 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    102119][000066] recording /recordings/mic_flip_lr_79.wav elapsed=28s bytes=915456 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    103143][000067] recording /recordings/mic_flip_lr_79.wav elapsed=29s bytes=948224 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    103689][000068] closed /recordings/mic_flip_lr_79.wav bytes=960512
+case flip_lr status=ok next_case_in=30s
+[    133689][000069] microphone inactive
+[    133690][000070] config updated: data=38 clk=39 select=48 left=1
+
+Starting case 3/4: swap_pins data=38 clk=39 select=48 left=1
+
+Speak this sentence clearly 3 times during the test:
+"Testing T-Beam microphone case swap_pins. One two three four five."
+Look for console lines where:
+  status=active
+  min and max change over time and are not equal
+  avgabs is not stuck at one repeated value
+If status=flat with min=max every second, that case is bad.
+[    133779][000071] opened /recordings/mic_swap_pins_139.wav
+E (133664) I2S: i2s_driver_uninstall(2048): I2S port 0 has not installed
+[    133780][000072] microphone active clk(ws)=39 data=38 select=48 left=1
+[    134785][000073] recording /recordings/mic_swap_pins_139.wav elapsed=1s bytes=30720 min=-32768 max=0 avgabs=30931 samples=15360 status=active
+[    135809][000074] recording /recordings/mic_swap_pins_139.wav elapsed=2s bytes=63488 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    136833][000075] recording /recordings/mic_swap_pins_139.wav elapsed=3s bytes=96256 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    137857][000076] recording /recordings/mic_swap_pins_139.wav elapsed=4s bytes=129024 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    137922][000077] file write failed wanted=2048 wrote=468
+[    137993][000078] closed /recordings/mic_swap_pins_139.wav bytes=129024
+case swap_pins status=failed next_case_in=30s
+[    167993][000079] microphone inactive
+[    167994][000080] config updated: data=38 clk=39 select=48 left=0
+
+Starting case 4/4: swap_flip data=38 clk=39 select=48 left=0
+
+Speak this sentence clearly 3 times during the test:
+"Testing T-Beam microphone case swap_flip. One two three four five."
+Look for console lines where:
+  status=active
+  min and max change over time and are not equal
+  avgabs is not stuck at one repeated value
+If status=flat with min=max every second, that case is bad.
+[    168083][000081] opened /recordings/mic_swap_flip_174.wav
+E (167968) I2S: i2s_driver_uninstall(2048): I2S port 0 has not installed
+[    168084][000082] microphone active clk(ws)=39 data=38 select=48 left=0
+[    169089][000083] recording /recordings/mic_swap_flip_174.wav elapsed=1s bytes=30720 min=-32768 max=0 avgabs=30931 samples=15360 status=active
+[    170113][000084] recording /recordings/mic_swap_flip_174.wav elapsed=2s bytes=63488 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    171137][000085] recording /recordings/mic_swap_flip_174.wav elapsed=3s bytes=96256 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    172161][000086] recording /recordings/mic_swap_flip_174.wav elapsed=4s bytes=129024 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    173185][000087] recording /recordings/mic_swap_flip_174.wav elapsed=5s bytes=161792 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    174209][000088] recording /recordings/mic_swap_flip_174.wav elapsed=6s bytes=194560 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    175233][000089] recording /recordings/mic_swap_flip_174.wav elapsed=7s bytes=227328 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    176257][000090] recording /recordings/mic_swap_flip_174.wav elapsed=8s bytes=260096 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    177281][000091] recording /recordings/mic_swap_flip_174.wav elapsed=9s bytes=292864 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    178305][000092] recording /recordings/mic_swap_flip_174.wav elapsed=10s bytes=325632 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    179329][000093] recording /recordings/mic_swap_flip_174.wav elapsed=11s bytes=358400 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    180353][000094] recording /recordings/mic_swap_flip_174.wav elapsed=12s bytes=391168 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    181377][000095] recording /recordings/mic_swap_flip_174.wav elapsed=13s bytes=423936 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    182401][000096] recording /recordings/mic_swap_flip_174.wav elapsed=14s bytes=456704 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    183425][000097] recording /recordings/mic_swap_flip_174.wav elapsed=15s bytes=489472 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    184449][000098] recording /recordings/mic_swap_flip_174.wav elapsed=16s bytes=522240 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    185473][000099] recording /recordings/mic_swap_flip_174.wav elapsed=17s bytes=555008 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    186497][000100] recording /recordings/mic_swap_flip_174.wav elapsed=18s bytes=587776 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    187521][000101] recording /recordings/mic_swap_flip_174.wav elapsed=19s bytes=620544 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    188545][000102] recording /recordings/mic_swap_flip_174.wav elapsed=20s bytes=653312 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    189569][000103] recording /recordings/mic_swap_flip_174.wav elapsed=21s bytes=686080 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    190593][000104] recording /recordings/mic_swap_flip_174.wav elapsed=22s bytes=718848 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    191617][000105] recording /recordings/mic_swap_flip_174.wav elapsed=23s bytes=751616 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    192641][000106] recording /recordings/mic_swap_flip_174.wav elapsed=24s bytes=784384 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    193665][000107] recording /recordings/mic_swap_flip_174.wav elapsed=25s bytes=817152 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    194689][000108] recording /recordings/mic_swap_flip_174.wav elapsed=26s bytes=849920 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    195713][000109] recording /recordings/mic_swap_flip_174.wav elapsed=27s bytes=882688 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    196737][000110] recording /recordings/mic_swap_flip_174.wav elapsed=28s bytes=915456 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    197761][000111] recording /recordings/mic_swap_flip_174.wav elapsed=29s bytes=948224 min=-30935 max=-30935 avgabs=30935 samples=16384 status=flat
+[    198306][000112] closed /recordings/mic_swap_flip_174.wav bytes=960512
+case swap_flip status=ok next_case_in=30s
+Disconnected ([Errno 5] Input/output error)
+Reconnecting to /dev/ttytCY ..^C
+(rnsenv) jlpoole@jp ~/workstation $ date
+Mon Apr 13 20:37:09 PDT 2026
+(rnsenv) jlpoole@jp ~/workstation $