MEMS microphone with ESP32

[Ethan25]

Hi,

I have been trying to interface my INMP441 (24bit digital MEMS microphone) with ESP32. It is pretty much a straight forward process but, every code that I find in GitHub or in some blog always gives me the mean value of the obtained data rather than the RAW data and also, this datasheet of this microphone tells us that it is a 24bit microphone but often people only use 16bits, why so ? what am I missing ?
1 - https://dronebotworkshop.com/esp32-i2s/

/*
  ESP32 I2S Microphone Sample
  esp32-i2s-mic-sample.ino
  Sample sound from I2S microphone, display on Serial Plotter
  Requires INMP441 I2S microphone

  DroneBot Workshop 2022
  https://dronebotworkshop.com
*/
void i2s_install() {
  // Set up I2S Processor configuration
  const i2s_config_t i2s_config = {
    .mode = i2s_mode_t(I2S_MODE_MASTER | I2S_MODE_RX),
    .sample_rate = 44100,
    .bits_per_sample = i2s_bits_per_sample_t(16),
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
    .communication_format = i2s_comm_format_t(I2S_COMM_FORMAT_STAND_I2S),
    .intr_alloc_flags = 0,
    .dma_buf_count = 8,
    .dma_buf_len = bufferLen,
    .use_apll = false
  };

  i2s_driver_install(I2S_PORT, &i2s_config, 0, NULL);
}

void loop() {
  // Get I2S data and place in data buffer
  size_t bytesIn = 0;
  esp_err_t result = i2s_read(I2S_PORT, &sBuffer, bufferLen, &bytesIn, portMAX_DELAY);

  if (result == ESP_OK)
  {
    // Read I2S data buffer
    int16_t samples_read = bytesIn / 8;
    if (samples_read > 0) {
      float mean = 0;
      for (int16_t i = 0; i < samples_read; ++i) {
        mean += (sBuffer[i]);
      }

      // Average the data reading
      mean /= samples_read;

      // Print to serial plotter
      Serial.println(mean);
    }
  }
}

2- https://github.com/0015/ThatProject/tree/master/ESP32_MICROPHONE/ESP32_INMP441_SETUP_ESP-2.X

void loop() {

  size_t bytesIn = 0;
  esp_err_t result = i2s_read(I2S_PORT, &sBuffer, bufferLen, &bytesIn, portMAX_DELAY);
  if (result == ESP_OK)
  {
    int samples_read = bytesIn / 8;
    if (samples_read > 0) {
      float mean = 0;
      for (int i = 0; i < samples_read; ++i) {
        mean += (sBuffer[i]);
      }
      mean /= samples_read;
      Serial.println(mean);
    }
  }
}

void i2s_install(){
  const i2s_config_t i2s_config = {
    .mode = i2s_mode_t(I2S_MODE_MASTER | I2S_MODE_RX),
    .sample_rate = 44100,
    .bits_per_sample = i2s_bits_per_sample_t(16),
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
    .communication_format = i2s_comm_format_t(I2S_COMM_FORMAT_STAND_I2S),
    .intr_alloc_flags = 0, // default interrupt priority
    .dma_buf_count = 8,
    .dma_buf_len = bufferLen,
    .use_apll = false
  };

  i2s_driver_install(I2S_PORT, &i2s_config, 0, NULL);
}