const int ledPin = 15;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(115200);
}

void loop() {
  digitalWrite(ledPin, LOW);   // LED ON (active LOW)
  Serial.println("LED ON");
  delay(500);
  digitalWrite(ledPin, HIGH);  // LED OFF (active LOW)
  Serial.println("LED OFF");
  delay(500);
}