const int ledMerah = 7;
     const int ledHijau = 8;
     void setup() {
       pinMode(ledMerah, OUTPUT);
       pinMode(ledHijau, OUTPUT);
     }
     void loop() {
       digitalWrite(ledMerah, HIGH);
       digitalWrite(ledHijau, LOW);
       delay(500); // jeda 500 ms
       digitalWrite(ledMerah, LOW);
       digitalWrite(ledHijau, HIGH);
       delay(500); // jeda 500 ms
     }