void setup() {
  // put your setup code here, to run once:

  pinMode(13, OUTPUT); // LED on board
}

void loop() {
  // put your main code here, to run repeatedly:

  // LED on board light :: use pinMode(13) in setup()
  digitalWrite(13, HIGH); // turn LED onboard on 
  delay(1000);
  digitalWrite(13, LOW); // turn LED onboard off 
  delay(1000);
}