ESP32 sine wave generator

esp32_sine_wave_speaker.cpp

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

// Use your existing pin defs
#define I2S_LRC    D0   // LRCLK / WS
#define I2S_BCLK   D1   // BCLK
#define I2S_DOUT   D2   // DIN to MAX98357A
#define I2S_SD_OUT D3   // SD / shutdown (mute) pin on MAX98357A

// Audio settings
const int   SAMPLE_RATE = 44100;    // Hz
const float TONE_FREQ   = 440.0f;   // Hz (A4)
const int   AMPLITUDE   = 20000;    // Max ~32767 for int16_t

void setupI2S() {
  i2s_config_t i2s_config = {
    .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_ONLY_RIGHT,  // mono is fine
    .communication_format = I2S_COMM_FORMAT_STAND_MSB,
    .intr_alloc_flags = 0,
    .dma_buf_count = 8,
    .dma_buf_len = 64,
    .use_apll = false,
    .tx_desc_auto_clear = true,
    .fixed_mclk = 0
  };

  i2s_pin_config_t pin_config = {
    .bck_io_num = I2S_BCLK,
    .ws_io_num  = I2S_LRC,
    .data_out_num = I2S_DOUT,
    .data_in_num = I2S_PIN_NO_CHANGE
  };

  // Install and start I2S driver
  i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
  i2s_set_pin(I2S_NUM_0, &pin_config);
  i2s_set_clk(I2S_NUM_0, SAMPLE_RATE, I2S_BITS_PER_SAMPLE_16BIT, I2S_CHANNEL_MONO);
}

void setup() {
  Serial.begin(115200);
  delay(1000);
  Serial.println("Starting sine wave test...");

  // Unmute MAX98357A
  pinMode(I2S_SD_OUT, OUTPUT);
  digitalWrite(I2S_SD_OUT, HIGH);

  setupI2S();
}

void loop() {
  // Generate a small buffer of sine samples and send via I2S
  const int NUM_SAMPLES = 256;
  static float phase = 0.0f;
  const float phaseInc = 2.0f * PI * TONE_FREQ / SAMPLE_RATE;

  int16_t samples[NUM_SAMPLES];

  for (int i = 0; i < NUM_SAMPLES; i++) {
    samples[i] = (int16_t)(sin(phase) * AMPLITUDE);
    phase += phaseInc;
    if (phase > 2.0f * PI) {
      phase -= 2.0f * PI;
    }
  }

  size_t bytesWritten;
  i2s_write(I2S_NUM_0, samples, sizeof(samples), &bytesWritten, portMAX_DELAY);
}