POC voice recorder for M5Stack Fire with a M5 Go Base. Compiles in the Arduino IDE.

voiceRecorder.ino

// https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/adc.html

/* this example has to be compiled with PSRAM enabled. */
#include <M5Stack.h>
#include <driver/adc.h>

#define MICROPHONE             34
#define SPEAKER                25
#define BACKLIGHT              32
#define BUFFER_SIZE            1000*1000
#define SAMPLING_FREQUENCY     22050

#define LOWNOISE               true /* set to false to enable backlight dimming */

TFT_eSPI tft = TFT_eSPI();

// set log level to debug for output
void logMemory() {
  log_d("Used PSRAM: %d from: %d", ESP.getPsramSize() - ESP.getFreePsram(), ESP.getPsramSize());
}

int8_t*                           sampleBuffer;
uint32_t                          allocatedSamples;
uint32_t                          currentSample{0};
uint32_t                          lastSample{0};
static hw_timer_t *               sampleTimer{NULL}; /* only one timer is (re)used for both sampling and playback */
unsigned int                      sampling_period_us = round(1000000 * (1.0 / SAMPLING_FREQUENCY));
bool                              samplerRunning{false};

static void IRAM_ATTR _sampleISR() {
  if (currentSample >= BUFFER_SIZE) {
    timerEnd(sampleTimer);
    sampleTimer = NULL;
    lastSample = currentSample;
  }
  else
    sampleBuffer[currentSample++] = adc1_get_raw(ADC1_GPIO34_CHANNEL) >> 1; // shifted 1 bit to the right because we set ADC_WIDTH_BIT_9
}

bool startSampler() {
  if (NULL != sampleTimer) return false;
  delay(170); /* to not record the click from releasing the button */
  currentSample = 0;
  sampleTimer = timerBegin(0, 80, true);
  timerAttachInterrupt(sampleTimer, &_sampleISR, true);
  timerAlarmWrite(sampleTimer, sampling_period_us, true);
  timerAlarmEnable(sampleTimer);
  samplerRunning = true;
  return true;
}

void setup() {
  pinMode(MICROPHONE, INPUT);
  pinMode(SPEAKER, OUTPUT);
  logMemory();

  tft.init();
  tft.setRotation(1);
  tft.fillScreen(TFT_BLACK);
  tft.setTextSize(2);
  tft.drawString("M5-Stack voicerecorder", 10, 5, 2);

  if (LOWNOISE) {
    pinMode(BACKLIGHT, OUTPUT);
    digitalWrite(BACKLIGHT, HIGH); // This gives the least noise
  } else {
    ledcAttachPin(BACKLIGHT, 0);
    ledcSetup(0, 1300, 16);
    ledcWrite(0, 0xFFFF / 16);     // Dimming the BACKLIGHT will produce more base noise
  }

  if (!ESP.getPsramSize()) {
    tft.setCursor(55, 40);
    tft.print("NO PSRAM FOUND!");
    while (1) delay(100);
  }

  sampleBuffer = (int8_t*)ps_malloc(BUFFER_SIZE * sizeof(int8_t));

  if (!sampleBuffer) {
    Serial.println("Could not allocate sample buffer - SYSTEM HALTED");
    while (1) delay(1000);
  }

  tft.setCursor(15, 40);
  tft.printf("%3.1fkHz %5.1fkB %6.2fs", SAMPLING_FREQUENCY / 1000.0, (BUFFER_SIZE * sizeof(int8_t)) / 1000.0, BUFFER_SIZE / (float)SAMPLING_FREQUENCY);
  tft.drawString("REC", 45, 200, 2);
  tft.drawString("PLAY", 130, 200, 2);
  tft.drawString("STOP", 220, 200, 2);

  adc1_config_width(ADC_WIDTH_BIT_9);
}

void loop() {
  M5.update();
  if (!sampleTimer && M5.BtnA.pressedFor(5)) startSampler();
  if (!sampleTimer && M5.BtnB.pressedFor(5)) startPlayback();

  uint32_t pos = currentSample;
  tft.setCursor(85, 100);
  tft.printf("%3lu%% %6.2fs", map(pos, 0, BUFFER_SIZE - 1, 0, 100), pos / (float)SAMPLING_FREQUENCY);
  tft.setCursor(60, 130);
  tft.printf(" %7i/%7i", pos, BUFFER_SIZE);

  if (sampleTimer && M5.BtnC.pressedFor(5)) {
    if (samplerRunning) {
      lastSample = currentSample;
      samplerRunning = false;
    }
    timerAlarmDisable(sampleTimer);
    timerEnd(sampleTimer);
    sampleTimer = NULL;
  }
  delay(5);
}

void IRAM_ATTR _playThroughDAC_ISR() {
  if (currentSample >= lastSample) {
    timerEnd(sampleTimer);
    sampleTimer = NULL;
    dacWrite(SPEAKER, 0);
  }
  else
    dacWrite(SPEAKER, sampleBuffer[currentSample++]);
}

bool startPlayback() {
  if (NULL != sampleTimer) return false;
  currentSample = 0;
  sampleTimer = timerBegin(0, 80, true);
  timerAttachInterrupt(sampleTimer, &_playThroughDAC_ISR, true);
  timerAlarmWrite(sampleTimer, sampling_period_us, true);
  timerAlarmEnable(sampleTimer);
  return true;
}

Hello,
sorry to worry you but I try without success :-( your programm on my M5Stack Fire.
My issue is when I click on Button A and I try B to play nothing is playing....
Perhaps you need more info from me?

Thanks for your help

You are right, does not run anymore.

Just tried to compile and fix it. Did not work.

This code was a proof of concept.
I am currently working on a new version.

Should be fixed in with the latest commit to https://github.com/CelliesProjects/voiceRecorderM5

Thanks for your help, I have at the starting point : NO PSRAM FOUND. Perhaps I make a bad thing ?

You will need the M5Go base. https://docs.m5stack.com/#/en/base/m5go_bottom

And also PSRAM because without PSRAM you will end up with only 3-4 seconds of recording capacity.

Wahoo it works like a charm (I just forget to add build_flags=-DBOARD_HAS_PSRAM to enable the PSRAM). Thanks a lot for your great project.