High noise on INMP441 output

[Huyyuh2000]

Board

DOIT ESP32 Devkit V1, WEMOS LOLON32 Lite, Wemos D1 R32

Device Description

All hardware plain on breadboard

Hardware Configuration

INMP441_WS connected to D15 INMP441_SD connected to D13 INMP441_SCK connected to D2 INMP441_VDD connected to 3.3V Pin INMP441_GND connected to GND

Version

v2.0.2

IDE Name

Arduino IDE

Operating System

Windows 11 Home Single Language

Flash frequency

80MHz

PSRAM enabled

no

Upload speed

115200

Description

Hello, I recorded .wav file using INMP441 and the data was able to process (noise was at acceptable level). At the moment, when I am recording for collect data, the noise is very high. I have change wire, dev kit and sensor but the result are the same. Here are the link that I save 2 recorded file. The low noise is before I meet the problem. I have read #3939 and follow some suggestion like soldering 10K between SD and GND but still not working.

Sketch

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

#define I2S_WS 15
#define I2S_SD 13
#define I2S_SCK 2
#define I2S_PORT I2S_NUM_0
#define I2S_SAMPLE_RATE   (16000)
#define I2S_SAMPLE_BITS   (16)
#define I2S_READ_LEN      (16 * 1024)
#define RECORD_TIME       (30) //Seconds
#define I2S_CHANNEL_NUM   (1)
#define FLASH_RECORD_SIZE (I2S_CHANNEL_NUM * I2S_SAMPLE_RATE * I2S_SAMPLE_BITS / 8 * RECORD_TIME)

File file;
const char filename[] = "/recording.wav";
const int headerSize = 44;

void setup() {
  // put your setup code here, to run once:

  Serial.begin(115200);
  SPIFFSInit();
  i2sInit();
  xTaskCreate(i2s_adc, "i2s_adc", 1024 * 3, NULL, 1, NULL);
}

void loop() {
  // put your main code here, to run repeatedly:

}

void SPIFFSInit(){
  if(!SPIFFS.begin(true)){
    Serial.println("SPIFFS initialisation failed!");
    while(1) yield();
  }
  SPIFFS.remove("/test.wav");
  SPIFFS.remove(filename);
  file = SPIFFS.open(filename, FILE_WRITE);
  if(!file){
    Serial.println("File is not available!");
  }

  byte header[headerSize];
  wavHeader(header, FLASH_RECORD_SIZE);

  file.write(header, headerSize);
  listSPIFFS();
}

void i2sInit(){
  esp_err_t err;
  i2s_config_t i2s_config = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),
    .sample_rate = I2S_SAMPLE_RATE,
    .bits_per_sample = i2s_bits_per_sample_t(I2S_SAMPLE_BITS), 
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
    .communication_format = i2s_comm_format_t(I2S_COMM_FORMAT_STAND_I2S | I2S_COMM_FORMAT_STAND_MSB),
    .intr_alloc_flags = 0,
    .dma_buf_count = 8,
    .dma_buf_len = 1024,
    .use_apll = 1
  };

  err = i2s_driver_install(I2S_PORT, &i2s_config, 0, NULL);
  if (err!=ESP_OK) {
    Serial.println("Failed to install driver");
  } else {
    Serial.println("Installed driver");
  }

  const i2s_pin_config_t pin_config = {
    .bck_io_num = I2S_SCK,
    .ws_io_num = I2S_WS,
    .data_out_num = -1,
    .data_in_num = I2S_SD
  };

  err = i2s_set_pin(I2S_PORT, &pin_config);
  if (err!=ESP_OK) {
    Serial.println("Failed to install pin");
  } else {
    Serial.println("Installed pin");
  }

}

void i2s_adc_data_scale(uint8_t * d_buff, uint8_t* s_buff, uint32_t len)
{
    uint32_t j = 0;
    uint32_t dac_value = 0;
    for (int i = 0; i < len; i += 2) {
        dac_value = ((((uint16_t) (s_buff[i + 1] & 0xf) << 8) | ((s_buff[i + 0]))));
        d_buff[j++] = 0;
        d_buff[j++] = dac_value * 256 / 2048;
    }
}

void i2s_adc(void *arg)
{
//    i2s_start(I2S_PORT);
    int i2s_read_len = I2S_READ_LEN;
    int flash_wr_size = 0;
    size_t bytes_read;

    char* i2s_read_buff = (char*) calloc(i2s_read_len, sizeof(char));
    uint8_t* flash_write_buff = (uint8_t*) calloc(i2s_read_len, sizeof(char));

    i2s_read(I2S_PORT, (void*) i2s_read_buff, i2s_read_len, &bytes_read, portMAX_DELAY);
    i2s_read(I2S_PORT, (void*) i2s_read_buff, i2s_read_len, &bytes_read, portMAX_DELAY);

    Serial.println(" *** Recording Start *** ");
    while (flash_wr_size < FLASH_RECORD_SIZE) {
        //read data from I2S bus, in this case, from ADC.
        i2s_read(I2S_PORT, (void*) i2s_read_buff, i2s_read_len, &bytes_read, portMAX_DELAY);
        //example_disp_buf((uint8_t*) i2s_read_buff, 64);
        //save original data from I2S(ADC) into flash.
        i2s_adc_data_scale(flash_write_buff, (uint8_t*)i2s_read_buff, i2s_read_len);
        file.write((const byte*) flash_write_buff, i2s_read_len);
        flash_wr_size += i2s_read_len;
        ets_printf("Sound recording %u%%\n", flash_wr_size * 100 / FLASH_RECORD_SIZE);
        ets_printf("Never Used Stack Size: %u\n", uxTaskGetStackHighWaterMark(NULL));
    }
    file.close();

    free(i2s_read_buff);
    i2s_read_buff = NULL;
    free(flash_write_buff);
    flash_write_buff = NULL;
//    Serial.println("Finish free memory");
    listSPIFFS();
//    Serial.println("Finish lissSPIFFS function");
//    i2s_stop(I2S_PORT);
    vTaskDelete(NULL);
}

void example_disp_buf(uint8_t* buf, int length)
{
    printf("======\n");
    for (int i = 0; i < length; i++) {
        printf("%02x ", buf[i]);
        if ((i + 1) % 8 == 0) {
            printf("\n");
        }
    }
    printf("======\n");
}

void wavHeader(byte* header, int wavSize){
  header[0] = 'R';
  header[1] = 'I';
  header[2] = 'F';
  header[3] = 'F';
  unsigned int fileSize = wavSize + headerSize - 8;
  header[4] = (byte)(fileSize & 0xFF);
  header[5] = (byte)((fileSize >> 8) & 0xFF);
  header[6] = (byte)((fileSize >> 16) & 0xFF);
  header[7] = (byte)((fileSize >> 24) & 0xFF);
  header[8] = 'W';
  header[9] = 'A';
  header[10] = 'V';
  header[11] = 'E';
  header[12] = 'f';
  header[13] = 'm';
  header[14] = 't';
  header[15] = ' ';
  header[16] = 0x10;
  header[17] = 0x00;
  header[18] = 0x00;
  header[19] = 0x00;
  header[20] = 0x01;
  header[21] = 0x00;
  header[22] = 0x01;
  header[23] = 0x00;
  header[24] = 0x80;
  header[25] = 0x3E;
  header[26] = 0x00;
  header[27] = 0x00;
  header[28] = 0x00;
  header[29] = 0x7D;
  header[30] = 0x00;
  header[31] = 0x00;
  header[32] = 0x02;
  header[33] = 0x00;
  header[34] = 0x10;
  header[35] = 0x00;
  header[36] = 'd';
  header[37] = 'a';
  header[38] = 't';
  header[39] = 'a';
  header[40] = (byte)(wavSize & 0xFF);
  header[41] = (byte)((wavSize >> 8) & 0xFF);
  header[42] = (byte)((wavSize >> 16) & 0xFF);
  header[43] = (byte)((wavSize >> 24) & 0xFF);

}

void listSPIFFS(void) {
  Serial.println(F("\r\nListing SPIFFS files:"));
  static const char line[] PROGMEM =  "=================================================";

  Serial.println(FPSTR(line));
  Serial.println(F("  File name                              Size"));
  Serial.println(FPSTR(line));

  fs::File root = SPIFFS.open("/");
  if (!root) {
    Serial.println(F("Failed to open directory"));
    return;
  }
  if (!root.isDirectory()) {
    Serial.println(F("Not a directory"));
    return;
  }

  fs::File file = root.openNextFile();
  while (file) {

    if (file.isDirectory()) {
      Serial.print("DIR : ");
      String fileName = file.name();
      Serial.print(fileName);
    } else {
      String fileName = file.name();
      Serial.print("  " + fileName);
      // File path can be 31 characters maximum in SPIFFS
      int spaces = 33 - fileName.length(); // Tabulate nicely
      if (spaces < 1) spaces = 1;
      while (spaces--) Serial.print(" ");
      String fileSize = (String) file.size();
      spaces = 10 - fileSize.length(); // Tabulate nicely
      if (spaces < 1) spaces = 1;
      while (spaces--) Serial.print(" ");
      Serial.println(fileSize + " bytes");
    }

    file = root.openNextFile();
  }

  Serial.println(FPSTR(line));
  Serial.println();
  delay(1000);
}

Debug Message

None

Other Steps to Reproduce

No response

I have checked existing issues, online documentation and the Troubleshooting Guide

• [X] I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[Huyyuh2000]

@PilnyTomas Please help me. Thanks in advance.

[PilnyTomas]

Hi @Huyyuh2000, thanks for creating the issue. Let me understand some things:

• Do you use some pre-soldered dev board with the INMP441, or did you make all the soldering yourself?
• What bits-per-second does the microphone transmit?
• The recorded data were ok, but after some change, it was broken?
  • What was the change that broke it?

[Huyyuh2000]

Hi @PilnyTomas, I soldered all the pin header for each sensor by myself, I config sample rate is 16kHz, 16 bit depth and 1 channel so that 256kbps, I don't change anything, after recorded I thought It was ok so move to another part of my project. When I get back to compile everything, I meet this problem

[PilnyTomas]

How did you manage to set up 16 bit depth on the microphone? Can you please send a block diagram of the connection for the microphone + a photo from the bottom side of the board with the microphone?

[Huyyuh2000]

Hi @PilnyTomas , About set up 16 bit depth, I config .bits_per_sample = i2s_bits_per_sample_t(I2S_SAMPLE_BITS) which I2S_SAMPLE_BITS is defined as (16). Here are all the things that you require: link

[PilnyTomas]

That is a setup in the ESP I2S module. My question was about the microphone. How do you know the microphone is outputting 16 bits per sample?

[Huyyuh2000]

Sorry, I don't know, Is there any way to check the output of the microphone?

[PilnyTomas]

Usually, the first thing is to read the documentation for the chip you want to use. I don't know the chip you are using. Please read the documentation and let me know what setup the microphone expects.

[Huyyuh2000]

The datasheet said that the microphone output is industry-standard 24-bit I²S interface.

[PilnyTomas]

Cool. Is the picture from the documentation, because there is depicted 32 bit per sample format. Try setting up 24 and 32 to see which one works.

[Huyyuh2000]

Hello, I tried change bit per sample and other parameters that come with it but there is still having noise. I found the reason why there a lot of noise was the L/R pin unconected. I watch some instructions and said that the sensor will auto set to ONLY_LEFT_CHANNEL if the pin is unconected. Seem like by unconecting the pin to Vdd or GND cause the problem.

[aliyou-sn]

Hello, please how do you solve this problem, i connect L\R pin to ground, I’m not getting any audio

[CaptHigh]

Hello, please how do you solve this problem, i connect L\R pin to ground, I’m not getting any audio

If You are using Arduino Framework with ESP32 then try connecting the L/R pin with GND and then set the input channel .channel_format = I2S_CHANNEL_FMT_ONLY_RIGHT,

Using this approach worked for me, try the Left channel if the Right one doesn't work

[Vegethalia]

Hello, do you remember if changing the bits_x_sample from 16 to 24/32 made any difference for you?

I'm receiving audio samples without problems and the quality is good (using a very similar configuration of the I2S as the one shown in the 1st post), but the "volume" of the samples is extremely low: The 4 "veritical lines" are 4 claps that I did just in front of the mic.

I don't know how to make it "louder".... of course I can "scale up" the signal, but the quality then is horrible.

[Vegethalia]

Ok I'll answer myself, just in case this serves someone else: The problem was that I had configured the I2S in 16 bit mode, and then I was only capturing the MSB of the bit stream. If I configured 24 bits, then the stream was garbled. The solution is to configure I2S in 32 bits mode and when reading, each sample takes 4 bytes and one must be discarted. Like this:

REAL_BYTES_X_SAMPLE=4;

i2s_read(I2S_NUM_0, (void*)dataOrig, buffSizeOrig, &bytesRead, portMAX_DELAY);
uint16_t samplesRead = bytesRead / REAL_BYTES_X_SAMPLE;
for (int i = 0; i < samplesRead; i++) {
    byteIndex = i * REAL_BYTES_X_SAMPLE;
    int32_t value = ((int32_t*)(dataOrig + byteIndex))[0]>>8;
}