const int ledPin = 29; // Built-in LED (change if using external)

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
  while (!Serial); // Wait for serial to connect (for native USB)
}

void loop() {
  if (Serial.available()) {
    String cmd = Serial.readStringUntil('\n');
    cmd.trim(); // Clean up input
    
    if (cmd == "ON") {
      digitalWrite(ledPin, HIGH);
    } else if (cmd == "OFF") {
      digitalWrite(ledPin, LOW);
    }
  }
}