1  #define ledPin 2
 2  
 3  int ledState = 0;
 4  
 5  void setup() {
 6    pinMode(ledPin, OUTPUT);
 7    digitalWrite(ledPin, ledState);
 8  }
 9  
10  void loop() {
11    digitalWrite(ledPin, !ledState);
12    ledState = !ledState;
13    delay(1000);
14  }