const int ledPin = 13; // On-board LED
const int interruptPin = 2;
volatile bool event = false;
 
void eventISR(){
    event = true;   
}
void setup() {
    pinMode(interruptPin, INPUT);
    pinMode(ledPin, OUTPUT);
    attachInterrupt(digitalPinToInterrupt(interruptPin), eventISR, RISING);
}
 
void loop() {
    if(event){
        digitalWrite(ledPin, HIGH);
        delay(500);
        digitalWrite(ledPin, LOW);
        event = false;
    }
}