Here is the sample code I'm using
I believe that the module has a built-in microphone.

As output of this code, only 0 is displayed.

Can someone please help me out 🙏?

#include <M5StickCPlus.h>
#include <driver/i2s.h>

#define SAMPLE_RATE 16000
#define SAMPLES 256

void setup() {
  M5.begin();
  Serial.begin(115200);

  // I2S config
  i2s_config_t i2s_config = {
      .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),
      .sample_rate = SAMPLE_RATE,
      .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
      .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
      .communication_format = I2S_COMM_FORMAT_I2S,
      .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
      .dma_buf_count = 8,
      .dma_buf_len = 64,
      .use_apll = false,
  };

  i2s_pin_config_t pin_config = {
      .bck_io_num = 0,
      .ws_io_num = 34,
      .data_out_num = I2S_PIN_NO_CHANGE,
      .data_in_num = 32
  };

  i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
  i2s_set_pin(I2S_NUM_0, &pin_config);

  Serial.println("Mic test started...");
}

void loop() {
  int16_t buffer[SAMPLES];
  size_t bytesRead;
  i2s_read(I2S_NUM_0, (char *)buffer, SAMPLES * sizeof(int16_t), &bytesRead, portMAX_DELAY);

  // Print a few samples
  for (int i = 0; i < 10; i++) {
    Serial.println(buffer[i]);
  }

  delay(500);
}