void setup() {
  // initialize digital pin2  as an output.
  pinMode(2, OUTPUT);
}
 
// the loop function runs over and over again forever
void loop() {
  digitalWrite(2, HIGH); //turn the LED on (HIGH is the voltage level)
  delay(500);            //wait for 0.5 second
  digitalWrite(2, LOW);  //turn the LED off by making the voltage LOW
  delay(500);            //wait for 0.5 second
}