1. Introduction
- ESP32 has two I2S peripherals. They can be configured to input and output sample data. They also supports DMA to stream sample data without needing CPU operations. I2S output can also be routed directly to the Digital to Analog Converter output (GPIO25 and GPIO26) without needing external I2S codec.
- In this demo I will show you how to use Arduino ESP32 I2S to play wav music file from sdcard. I chose wav file because it is not compressed like mp3 file. So we need not to de-compress it.
- There are 2 demos for this post:
    1. I used external I2S codec, 2 speakers and 1 module micro sdcard.
    2. I Used internal DAC, 2 speakers and 1 module micro sdcard.
Figure: I used external I2S codec for this demo, 2 speakers and 1 module micro sdcard
2. Hardware
Connect hardware like below:
[ESP32 IO32 – CS MICROSD]
[ESP32 IO14 – MOSI MICROSD]
[ESP32 IO13 – MISO MICROSD]
[ESP32 IO27 – SCK MICROSD]
[ESP32 IO26 – I2S codec BCK]
[ESP32 IO22 – I2S codec DATA]
[ESP32 IO25 – I2S codec LRCK]
[ESP32 GND – I2S codec GND]
[ESP32 GND – GND MICROSD]
[5V – VCC MICROSD]
[5V – I2S codec]
3. Software
- We will re-use Demo 7 for sdcard reading and I2S driver here. You can download the document about the wav file format here.
Note: You can down full project including wav file sample : https://github.com/nhatuan84/esp32-i2s-sdcard-wav-player
3.1 The code with external DAC  
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#include <mySD.h>
#include "driver/i2s.h"
#include "freertos/queue.h"

#define CCCC(c1, c2, c3, c4)    ((c4 << 24) | (c3 << 16) | (c2 << 8) | c1)

/* these are data structures to process wav file */
typedef enum headerState_e {
    HEADER_RIFF, HEADER_FMT, HEADER_DATA, DATA
} headerState_t;

typedef struct wavRiff_s {
    uint32_t chunkID;
    uint32_t chunkSize;
    uint32_t format;
} wavRiff_t;

typedef struct wavProperties_s {
    uint32_t chunkID;
    uint32_t chunkSize;
    uint16_t audioFormat;
    uint16_t numChannels;
    uint32_t sampleRate;
    uint32_t byteRate;
    uint16_t blockAlign;
    uint16_t bitsPerSample;
} wavProperties_t;
/* variables hold file, state of process wav file and wav file properties */    
File root;
headerState_t state = HEADER_RIFF;
wavProperties_t wavProps;

//i2s configuration 
int i2s_num = 0; // i2s port number
i2s_config_t i2s_config = {
     .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
     .sample_rate = 36000,
     .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
     .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
     .communication_format = (i2s_comm_format_t)(I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB),
     .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1, // high interrupt priority
     .dma_buf_count = 8,
     .dma_buf_len = 64   //Interrupt level 1
    };
    
i2s_pin_config_t pin_config = {
    .bck_io_num = 26, //this is BCK pin
    .ws_io_num = 25, // this is LRCK pin
    .data_out_num = 22, // this is DATA output pin
    .data_in_num = -1   //Not used
};
//
void debug(uint8_t *buf, int len){
  for(int i=0;i<len;i++){
    Serial.print(buf[i], HEX);
    Serial.print("\t");
  }
  Serial.println();
}
/* write sample data to I2S */
int i2s_write_sample_nb(uint32_t sample){
  return i2s_write_bytes((i2s_port_t)i2s_num, (const char *)&sample, sizeof(uint32_t), 100);
}
/* read 4 bytes of data from wav file */
int read4bytes(File file, uint32_t *chunkId){
  int n = file.read((uint8_t *)chunkId, sizeof(uint32_t));
  return n;
}

/* these are function to process wav file */
int readRiff(File file, wavRiff_t *wavRiff){
  int n = file.read((uint8_t *)wavRiff, sizeof(wavRiff_t));
  return n;
}
int readProps(File file, wavProperties_t *wavProps){
  int n = file.read((uint8_t *)wavProps, sizeof(wavProperties_t));
  return n;
}

void setup()
{
  Serial.begin(115200);
  Serial.print("Initializing SD card...");
  if (!SD.begin(32, 14, 13, 27)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");
  delay(1000);
  /* open wav file and process it */
  root = SD.open("T.WAV");
  if (root) {    
    int c = 0;
    int n;
    while (root.available()) {
      switch(state){
        case HEADER_RIFF:
        wavRiff_t wavRiff;
        n = readRiff(root, &wavRiff);
        if(n == sizeof(wavRiff_t)){
          if(wavRiff.chunkID == CCCC('R', 'I', 'F', 'F') && wavRiff.format == CCCC('W', 'A', 'V', 'E')){
            state = HEADER_FMT;
            Serial.println("HEADER_RIFF");
          }
        }
        break;
        case HEADER_FMT:
        n = readProps(root, &wavProps);
        if(n == sizeof(wavProperties_t)){
          state = HEADER_DATA;
        }
        break;
        case HEADER_DATA:
        uint32_t chunkId, chunkSize;
        n = read4bytes(root, &chunkId);
        if(n == 4){
          if(chunkId == CCCC('d', 'a', 't', 'a')){
            Serial.println("HEADER_DATA");
          }
        }
        n = read4bytes(root, &chunkSize);
        if(n == 4){
          Serial.println("prepare data");
          state = DATA;
        }
        //initialize i2s with configurations above
        i2s_driver_install((i2s_port_t)i2s_num, &i2s_config, 0, NULL);
        i2s_set_pin((i2s_port_t)i2s_num, &pin_config);
        //set sample rates of i2s to sample rate of wav file
        i2s_set_sample_rates((i2s_port_t)i2s_num, wavProps.sampleRate); 
        break; 
        /* after processing wav file, it is time to process music data */
        case DATA:
        uint32_t data; 
        n = read4bytes(root, &data);
        i2s_write_sample_nb(data); 
        break;
      }
    }
    root.close();
  } else {
    Serial.println("error opening test.txt");
  }
  i2s_driver_uninstall((i2s_port_t)i2s_num); //stop & destroy i2s driver 
  Serial.println("done!");
}

void loop()
{
}
3.2 The code with built-in DAC
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#include <mySD.h>
#include "driver/i2s.h"
#include "freertos/queue.h"

#define CCCC(c1, c2, c3, c4)    ((c4 << 24) | (c3 << 16) | (c2 << 8) | c1)

/* these are data structures to process wav file */
typedef enum headerState_e {
    HEADER_RIFF, HEADER_FMT, HEADER_DATA, DATA
} headerState_t;

typedef struct wavRiff_s {
    uint32_t chunkID;
    uint32_t chunkSize;
    uint32_t format;
} wavRiff_t;

typedef struct wavProperties_s {
    uint32_t chunkID;
    uint32_t chunkSize;
    uint16_t audioFormat;
    uint16_t numChannels;
    uint32_t sampleRate;
    uint32_t byteRate;
    uint16_t blockAlign;
    uint16_t bitsPerSample;
} wavProperties_t;
/* variables hold file, state of process wav file and wav file properties */    
File root;
headerState_t state = HEADER_RIFF;
wavProperties_t wavProps;

//i2s configuration 
int i2s_num = 0; // i2s port number
i2s_config_t i2s_config = {
     .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX | I2S_MODE_DAC_BUILT_IN),
     .sample_rate = 44100,
     .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT, /* the DAC module will only take the 8bits from MSB */
     .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
     .communication_format = (i2s_comm_format_t)I2S_COMM_FORMAT_I2S_MSB,
     .intr_alloc_flags = 0, // default interrupt priority
     .dma_buf_count = 8,
     .dma_buf_len = 64,
     .use_apll = 0
    };
//
void debug(uint8_t *buf, int len){
  for(int i=0;i<len;i++){
    Serial.print(buf[i], HEX);
    Serial.print("\t");
  }
  Serial.println();
}
/* write sample data to I2S */
int i2s_write_sample_nb(uint8_t sample){
  return i2s_write_bytes((i2s_port_t)i2s_num, (const char *)&sample, sizeof(uint8_t), 100);
}
/* read 4 bytes of data from wav file */
int read4bytes(File file, uint32_t *chunkId){
  int n = file.read((uint8_t *)chunkId, sizeof(uint32_t));
  return n;
}

int readbyte(File file, uint8_t *chunkId){
  int n = file.read((uint8_t *)chunkId, sizeof(uint8_t));
  return n;
}

/* these are function to process wav file */
int readRiff(File file, wavRiff_t *wavRiff){
  int n = file.read((uint8_t *)wavRiff, sizeof(wavRiff_t));
  return n;
}
int readProps(File file, wavProperties_t *wavProps){
  int n = file.read((uint8_t *)wavProps, sizeof(wavProperties_t));
  return n;
}

void setup()
{
  Serial.begin(115200);
  Serial.print("Initializing SD card...");
  if (!SD.begin(32, 14, 13, 27)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");
  delay(1000);
  /* open wav file and process it */
  root = SD.open("T.WAV");
  if (root) {    
    int c = 0;
    int n;
    while (root.available()) {
      switch(state){
        case HEADER_RIFF:
        wavRiff_t wavRiff;
        n = readRiff(root, &wavRiff);
        if(n == sizeof(wavRiff_t)){
          if(wavRiff.chunkID == CCCC('R', 'I', 'F', 'F') && wavRiff.format == CCCC('W', 'A', 'V', 'E')){
            state = HEADER_FMT;
            Serial.println("HEADER_RIFF");
          }
        }
        break;
        case HEADER_FMT:
        n = readProps(root, &wavProps);
        if(n == sizeof(wavProperties_t)){
          state = HEADER_DATA;
        }
        break;
        case HEADER_DATA:
        uint32_t chunkId, chunkSize;
        n = read4bytes(root, &chunkId);
        if(n == 4){
          if(chunkId == CCCC('d', 'a', 't', 'a')){
            Serial.println("HEADER_DATA");
          }
        }
        n = read4bytes(root, &chunkSize);
        if(n == 4){
          Serial.println("prepare data");
          state = DATA;
        }
        //initialize i2s with configurations above
        i2s_driver_install((i2s_port_t)i2s_num, &i2s_config, 0, NULL);
        i2s_set_pin((i2s_port_t)i2s_num, NULL);
        //set sample rates of i2s to sample rate of wav file
        i2s_set_sample_rates((i2s_port_t)i2s_num, wavProps.sampleRate); 
        break; 
        /* after processing wav file, it is time to process music data */
        case DATA:
        uint8_t data; 
        n = readbyte(root, &data);
        i2s_write_sample_nb(data); 
        break;
      }
    }
    root.close();
  } else {
    Serial.println("error opening test.txt");
  }
  i2s_driver_uninstall((i2s_port_t)i2s_num); //stop & destroy i2s driver 
  Serial.println("done!");
}

void loop()
{
}
4. Result