I2S does not work in STEREO with INMP441

[andreyVylix]

I connected two microphones according to the following scheme. Both microphones work in mono format. When I try to get a signal in stereo format (RIGHT_LFET), the useful signal is only on the left channel ( x = 0, 2, 4 .... 418), and random values are received from the right channel (x = 1,3...419). It is also unclear to me why half (x = 420...819) the read values are 0, in any I2S format. Because of this, in stereo mode, there is only 820/4 per channel.
The main problem is how to make INMP441 work in stereo format ?

Code: Select all

#include <Arduino.h>
#include "driver/i2s.h"
#include <cmath>

#define I2S_WS_1 19
#define I2S_SD_1 21
#define I2S_SCK_1 18

static uint32_t sample_buffer_size = 820;
static uint32_t sampling_rate = 44100;
static signed short sampleBuffer_1[sample_buffer_size];

static int i2s_init(int pin_SCK, int pin_WS, int pin_SD, int port ,i2s_channel_fmt_t Format )
{
  i2s_config_t i2s_config = {
      .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX ),
      .sample_rate = sampling_rate,
      .bits_per_sample = (i2s_bits_per_sample_t)16,
      .channel_format = Format,
      .communication_format = I2S_COMM_FORMAT_STAND_I2S,
      .dma_buf_count = 4,
      .dma_buf_len = sample_buffer_size,
      .use_apll = false,
      .tx_desc_auto_clear = false,
      .fixed_mclk = -1,
  };
  i2s_pin_config_t pin_config = {
      .bck_io_num = pin_SCK, // IIS_SCLK
      .ws_io_num = pin_WS,   // IIS_LCLK
      .data_out_num = -1,    // IIS_DSIN
      .data_in_num = pin_SD, // IIS_DOUT
  };
  esp_err_t ret = 0;

  ret = i2s_driver_install((i2s_port_t)port, &i2s_config, 0, NULL);
  if (ret != ESP_OK)
  {
    Serial.println("Error in i2s_driver_install");
  }

  ret = i2s_set_pin((i2s_port_t)port, &pin_config);
  if (ret != ESP_OK)
  {
    Serial.println("Error in i2s_set_pin");
  }

  ret = i2s_zero_dma_buffer((i2s_port_t)port);
  if (ret != ESP_OK)
  {
    Serial.println("Error in initializing dma buffer with 0");
  }

  return int(ret);
}

void i2s_microphone1(void *arg)
{
  if (i2s_init(I2S_SCK_1, I2S_WS_1, I2S_SD_1, 1, I2S_CHANNEL_FMT_RIGHT_LEFT))
    Serial.println("Failed to start I2S_1!");
  const uint16_t i2s_bytes_to_read = sample_buffer_size;
  size_t bytes_read;
  while (true)
  {
      bytes_read = 0;
      i2s_read((i2s_port_t)1, (void *)sampleBuffer_1, i2s_bytes_to_read, &bytes_read, portMAX_DELAY); 
      for (int x = 0; x < bytes_read; x+=2)
      {
        if (abs(sampleBuffer_1[x]) > 1000 )
          Serial.println("channel left = " + (String)sampleBuffer_1[x] + " channel right  = " + (String)sampleBuffer_1[x+1]  );
      }
    }
}
void setup()
{
  Serial.begin(115200);
  xTaskCreate(i2s_microphone1, "I2S_microphone_1", 1024, (void *)sample_buffer_size, 1, NULL);
}

void loop()
{
  vTaskDelete(NULL);
}