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I have configured I2S to reproduce files with an ESP32 and a MAX98357A from and SD card. The problem is that it reproduces the files way too fast, like they are sped up * 100. Here is my (simplified) code:
#define I2S_DOUT 25
#define I2S_BCLK 27
#define I2S_LRC 26
void setup() {
// Start SD card and sqlite
SPI.begin();
if (!SD.begin()) {
Serial.println("SD card not found");
while (1) {};
// Configure I2S
i2s_config_t i2s_config = {
.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
.sample_rate = 44100,
.bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
.channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
.communication_format = I2S_COMM_FORMAT_I2S_MSB,
.intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
.dma_buf_count = 2,
.dma_buf_len = 1024,
.tx_desc_auto_clear = true,
i2s_pin_config_t pin_config = {
.bck_io_num = I2S_BCLK,
.ws_io_num = I2S_LRC,
.data_out_num = I2S_DOUT,
.data_in_num = -1,
i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
i2s_set_pin(I2S_NUM_0, &pin_config);
i2s_set_dac_mode(I2S_DAC_CHANNEL_RIGHT_EN);
i2s_set_sample_rates(I2S_NUM_0, 44100);
void loop() {
// Play the audio file
string filename = "/audios/" + text + ".wav";
File file = SD.open(filename.c_str());
if (!file) {
Serial.println("Failed to open file for reading");
return;
const size_t buffer_size = 512;
uint8_t buffer[buffer_size];
size_t bytes_read;
size_t bytes_written;
while (file.available() && (bytes_read = file.read(buffer, buffer_size)) > 0) {
i2s_write(I2S_NUM_0, buffer, bytes_read, &bytes_written, portMAX_DELAY);
if (bytes_read == 0) break;
file.close();
How do I configure it correctly?
So I figured it out (a somewhat long time ago) but forgot to post here hahaha.
Basically, the i2s_config_t was not properly configured. Here's a corrected version:
i2s_config_t i2s_config = {
.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
.sample_rate = 44100,
.bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
.communication_format = I2S_COMM_FORMAT_I2S_MSB,
.intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
.dma_buf_count = 8,
.dma_buf_len = 1024,
.use_apll = false,
.tx_desc_auto_clear = true,
If you compare, the .channel_format configuration changes from I2S_CHANNEL_FMT_RIGHT_LEFT to I2S_CHANNEL_FMT_ONLY_LEFT. This is important because when using RIGHT_LEFT and only using one amplifier, 2 sound outputs were sent but only one amp was receiving them, causing the sound to play at twice the speed. Now, the .dma_buf_count was increased to 8, and added the .use_apll config, because I saw it somewhere else, I don't really know what it does hahaha.
There are other things.
In the setup for the i2s communication, I didn't include
i2s_set_dac_mode(I2S_DAC_CHANNEL_RIGHT_EN);
i2s_set_sample_rates(I2S_NUM_0, 44100);
And created a new function, play_sound.
Here's the complete code:
// sound.cpp
#include <sound.h>
bool parseWavHeader(File &file, WavHeader &header) {
if (file.read() != 'R' || file.read() != 'I' || file.read() != 'F' || file.read() != 'F') {
Serial.println("Invalid WAV file");
return false;
file.seek(22);
header.num_channels = file.read() | (file.read() << 8);
header.sample_rate = file.read() | (file.read() << 8) | (file.read() << 16) | (file.read() << 24);
file.seek(34);
header.bits_per_sample = file.read() | (file.read() << 8);
file.seek(44); // Skip to the audio data
return true;
void setup_sound() {
i2s_config_t i2s_config = {
.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
.sample_rate = 44100,
.bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
.communication_format = I2S_COMM_FORMAT_I2S_MSB,
.intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
.dma_buf_count = 8,
.dma_buf_len = 1024,
.use_apll = false,
.tx_desc_auto_clear = true,
i2s_pin_config_t pin_config = {
.bck_io_num = I2S_BCLK,
.ws_io_num = I2S_LRC,
.data_out_num = I2S_DOUT,
.data_in_num = -1,
i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
i2s_set_pin(I2S_NUM_0, &pin_config);
void play_sound(std::string text, fs::FS &SD) {
std::string filename = "/audios/" + text + ".wav";
File file = SD.open(filename.c_str());
if (!file) {
Serial.println("Failed to open file for reading");
while (1) delay(1);
WavHeader header;
if (!parseWavHeader(file, header)) {
Serial.println("Invalid WAV file");
return;
i2s_set_sample_rates(I2S_NUM_0, header.sample_rate);
const size_t buffer_size = 512;
uint8_t buffer[buffer_size];
size_t bytes_read;
size_t bytes_written;
while (file.available() && (bytes_read = file.read(buffer, buffer_size)) > 0) {
i2s_write(I2S_NUM_0, buffer, bytes_read, &bytes_written, portMAX_DELAY);
if (bytes_read == 0) break;
file.close();
// sound.h
#ifndef SOUND_H
#define SOUND_H
#include <SD.h>
#include <driver/i2s.h>
#define I2S_DOUT 25
#define I2S_BCLK 33
#define I2S_LRC 26
struct WavHeader {
uint32_t sample_rate;
uint16_t bits_per_sample;
uint16_t num_channels;
bool parseWavHeader(File &file, WavHeader &header);
void setup_sound();
void play_sound(std::string text, fs::FS &SD);
#endif // SOUND_H
Hope it helps you not go through the struggle I went through!
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