3W amplifier MAX98357A I2S DAC

#include <Arduino.h>

// Canonical beginner example for MAX98357A on Arduino Uno.
//
// Important:
// The Arduino Uno (AVR) cannot generate hardware I2S with the standard core,
// so this sketch demonstrates the wiring and control pins, then produces a very
// simple software-generated square-wave audio pattern on the data pin.
//
// Wiring used:
//   D9  -> BCLK
//   D8  -> LRC
//   D10 -> DIN
//   5V  -> VIN
//   GND -> GND

const uint8_t PIN_BCLK = 9;
const uint8_t PIN_LRC  = 8;
const uint8_t PIN_DIN  = 10;

const unsigned int toneHz = 440;
const unsigned long toneOnMs = 1000;
const unsigned long toneOffMs = 500;

void outputSquareWave(unsigned long durationMs, unsigned int frequencyHz) {
  // This does not create real I2S audio; it is only a simple beginner demo.
  // The MAX98357A requires an I2S-capable source for proper audio playback.
  unsigned long start = millis();
  unsigned long halfPeriodUs = 500000UL / frequencyHz;

  while (millis() - start < durationMs) {
    digitalWrite(PIN_DIN, HIGH);
    delayMicroseconds(halfPeriodUs);
    digitalWrite(PIN_DIN, LOW);
    delayMicroseconds(halfPeriodUs);
  }
}

void setup() {
  pinMode(PIN_BCLK, OUTPUT);
  pinMode(PIN_LRC, OUTPUT);
  pinMode(PIN_DIN, OUTPUT);

  digitalWrite(PIN_BCLK, LOW);
  digitalWrite(PIN_LRC, LOW);
  digitalWrite(PIN_DIN, LOW);

  Serial.begin(115200);
  Serial.println(F("MAX98357A example starting."));
  Serial.println(F("Arduino Uno does not support native I2S in the standard AVR core."));
  Serial.println(F("This sketch only demonstrates basic pin control on the labeled connections."));
}

void loop() {
  Serial.println(F("Tone ON"));
  outputSquareWave(toneOnMs, toneHz);

  Serial.println(F("Tone OFF"));
  digitalWrite(PIN_DIN, LOW);
  delay(toneOffMs);
}