How to play audio from
ESP32 with MAX98357A

espeak-ng -w /tmp/myclip.wav "your text here"

ffmpeg -i /path/to/source.wav -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i ~/mysound.wav -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i ~/Downloads/mysound.mp3 -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i ~/Videos/myvideo.mp4 -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i "/home/j/My Audio File.wav" -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -y -i /tmp/myclip.wav -ar 22050 -ac 1 -acodec pcm_s16le /tmp/clip_i2s.wav

import sys, wave, struct

input_file  = sys.argv[1]  # e.g. /tmp/clip_i2s.wav
output_file = sys.argv[2]  # e.g. clip.h

# wave module reads and strips the WAV header automatically -
# readframes() returns raw PCM samples only
with wave.open(input_file, 'rb') as f:
    raw = f.readframes(f.getnframes())

# unpack as signed 16-bit little-endian integers (pcm_s16le)
samples = struct.unpack('<' + str(len(raw)//2) + 'h', raw)

lines = [
    '#pragma once',
    'const int16_t audio_data[] = {',
]
chunks = [str(s) for s in samples]
for i in range(0, len(chunks), 16):
    lines.append('  ' + ', '.join(chunks[i:i+16]) + ',')
lines.append('};')
lines.append('const size_t audio_len = sizeof(audio_data);')

with open(output_file, 'w') as f:
    f.write('\n'.join(lines) + '\n')

print('Done: ' + str(len(samples)) + ' samples -> ' + output_file)

python3 wav_to_i2s_header.py /tmp/clip_i2s.wav clip.h

/*
 * We stand on the shoulders of giants when we build
 * with knowledge gained from others' efforts.
 * That doesn't make us giants. Be humble.
 * Create with care. Open source is the way.
 *
 * MAX98357A I2S - Tone Test
 * --------------------------
 * Generates a 440Hz sine wave via I2S to confirm
 * wiring and amp are working. No audio file needed.
 *
 * Board:   ESP32 Dev Board (38-pin) or ESP32-C3
 * Amp:     MAX98357A
 *
 * Wiring (ESP32 Dev Board):
 *   VIN  -> 5V      GND  -> GND
 *   BCLK -> GPIO27  LRC  -> GPIO14
 *   DIN  -> GPIO13  SD   -> not connected
 *
 * Wiring (ESP32-C3):
 *   VIN  -> 5V      GND  -> GND
 *   BCLK -> GPIO4   LRC  -> GPIO5
 *   DIN  -> GPIO6   SD   -> not connected
 *
 * Open source - MIT Licence
 * Electronic Zoology - field notes from the garage
 * https://electroniczoology.com/guides/how-to-play-audio-esp32-max98357a
 */

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

// ESP32 Dev Board (38-pin)
#define I2S_BCLK   27
#define I2S_LRCLK  14
#define I2S_DOUT   13
// ESP32-C3 - comment out the three lines above and uncomment these:
//#define I2S_BCLK   4
//#define I2S_LRCLK  5
//#define I2S_DOUT   6

#define SAMPLE_RATE 44100
#define FREQUENCY   440
#define AMPLITUDE   20000
#define BUF_SIZE    256

int16_t buf[BUF_SIZE];

void setup() {
  i2s_config_t cfg = {
    .mode                 = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
    .sample_rate          = SAMPLE_RATE,
    .bits_per_sample      = I2S_BITS_PER_SAMPLE_16BIT,
    .channel_format       = I2S_CHANNEL_FMT_RIGHT_LEFT,
    .communication_format = I2S_COMM_FORMAT_STAND_I2S,
    .intr_alloc_flags     = ESP_INTR_FLAG_LEVEL1,
    .dma_buf_count        = 8,
    .dma_buf_len          = 64,
    .use_apll             = false,
    .tx_desc_auto_clear   = true,
  };

  i2s_pin_config_t pins = {
    .bck_io_num   = I2S_BCLK,
    .ws_io_num    = I2S_LRCLK,
    .data_out_num = I2S_DOUT,
    .data_in_num  = I2S_PIN_NO_CHANGE,
  };

  i2s_driver_install(I2S_NUM_0, &cfg, 0, NULL);
  i2s_set_pin(I2S_NUM_0, &pins);
}

void loop() {
  static uint32_t phase = 0;
  size_t written;

  for (int i = 0; i < BUF_SIZE; i += 2) {
    int16_t sample = (int16_t)(AMPLITUDE * sinf(2.0f * M_PI * FREQUENCY * phase / SAMPLE_RATE));
    buf[i]     = sample;
    buf[i + 1] = sample;
    phase++;
    if (phase >= SAMPLE_RATE) phase = 0;
  }

  i2s_write(I2S_NUM_0, buf, sizeof(buf), &written, portMAX_DELAY);
}

/*
 * We stand on the shoulders of giants when we build
 * with knowledge gained from others' efforts.
 * That doesn't make us giants. Be humble.
 * Create with care. Open source is the way.
 *
 * MAX98357A I2S Amplifier - ESP32 Dev Board
 * ------------------------------------------
 * Plays a 16-bit PCM audio clip stored in flash
 * via I2S to a MAX98357A amplifier and speaker.
 *
 * Board:   ESP32 Dev Board (38-pin) or ESP32-C3
 * Amp:     MAX98357A
 *
 * Wiring (ESP32 Dev Board):
 *   VIN  -> 5V      GND  -> GND
 *   BCLK -> GPIO27  LRC  -> GPIO14
 *   DIN  -> GPIO13  SD   -> not connected
 *
 * Wiring (ESP32-C3):
 *   VIN  -> 5V      GND  -> GND
 *   BCLK -> GPIO4   LRC  -> GPIO5
 *   DIN  -> GPIO6   SD   -> not connected
 *
 * Open source - MIT Licence
 * Electronic Zoology - field notes from the garage
 * https://electroniczoology.com/guides/how-to-play-audio-esp32-max98357a
 */

#include <driver/i2s.h>
#include "clip.h"

// ESP32 Dev Board (38-pin)
#define I2S_BCLK    27
#define I2S_LRCLK   14
#define I2S_DOUT    13
// ESP32-C3 - comment out the three lines above and uncomment these:
//#define I2S_BCLK   4
//#define I2S_LRCLK  5
//#define I2S_DOUT   6

#define SAMPLE_RATE 22050  // must match -ar value used in ffmpeg conversion
#define VOLUME      0.8f   // 0.0 = silent, 1.0 = max

#define BUF_SAMPLES 256
int16_t i2s_buf[BUF_SAMPLES * 2]; // stereo buffer

void setup() {
  i2s_config_t cfg = {
    .mode                 = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
    .sample_rate          = SAMPLE_RATE,
    .bits_per_sample      = I2S_BITS_PER_SAMPLE_16BIT,
    .channel_format       = I2S_CHANNEL_FMT_RIGHT_LEFT,
    .communication_format = I2S_COMM_FORMAT_STAND_I2S,
    .intr_alloc_flags     = ESP_INTR_FLAG_LEVEL1,
    .dma_buf_count        = 8,
    .dma_buf_len          = 64,
    .use_apll             = false,
    .tx_desc_auto_clear   = true,
  };

  i2s_pin_config_t pins = {
    .bck_io_num   = I2S_BCLK,
    .ws_io_num    = I2S_LRCLK,
    .data_out_num = I2S_DOUT,
    .data_in_num  = I2S_PIN_NO_CHANGE,
  };

  i2s_driver_install(I2S_NUM_0, &cfg, 0, NULL);
  i2s_set_pin(I2S_NUM_0, &pins);
}

void loop() {
  size_t total = audio_len / sizeof(int16_t);
  size_t written;

  for (size_t pos = 0; pos < total; pos += BUF_SAMPLES) {
    size_t count = min((size_t)BUF_SAMPLES, total - pos);
    for (size_t i = 0; i < count; i++) {
      int16_t sample = (int16_t)(audio_data[pos + i] * VOLUME);
      i2s_buf[i * 2]     = sample; // left
      i2s_buf[i * 2 + 1] = sample; // right
    }
    i2s_write(I2S_NUM_0, i2s_buf, count * 2 * sizeof(int16_t), &written, portMAX_DELAY);
  }
  delay(1000);
}