// #########################################
//        External LED Interfacing          
// #########################################
// 
//  Interface an LED to Arduino UNO (Hardware & Simulation)
// 
//  Check out the link for Code explanation and Hardware details
//  Link: 
//    http://tech.arunkumarn.in/blogs/arduino-uno/interfacing-led-to-arduino-uno/
// 

#define LED_1 8
#define LED_2 4

void setup() {
  // Initialize LED as output PIN
  pinMode(LED_1, OUTPUT);
  pinMode(LED_2, OUTPUT);

}

void loop() {
  // Turning ON External LED
  digitalWrite(LED_1, HIGH); // HIGH Logic
  digitalWrite(LED_2, LOW); // LOW Logic
  delay(2000);

  // Turning OFF External LED
  digitalWrite(LED_1, LOW);  // HIGH Logic
  digitalWrite(LED_2, HIGH); // LOW Logic
  delay(1000);

}