/******************************************************************
Turns an LED on for one second, then off for one second, repeatedly.

Arduinos have an on-board LED. On the UNO, MEGA and ZERO it is attached 
to digital pin 13. LED_BUILTIN is set to the correct LED pin independent 
of which board is used. 

******************************************************************/


void setup() { //  setup code, run once when it is powerd
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);       
}