#define LED_interrupt 9
#define interrupt 3
#define LED1 2

int a=0;

//volatile byte ledState = LOW;

void setup() {
  pinMode(LED_interrupt, OUTPUT);
  pinMode(LED1, OUTPUT);
  pinMode(interrupt, INPUT);
  attachInterrupt(digitalPinToInterrupt(interrupt), blinkLed, FALLING);
}
void loop() {
  if (a==0) 
    {
      digitalWrite(LED1, LOW);
      delay(500);

      digitalWrite(LED1, HIGH);
      delay(500);
    }
  else {
  digitalWrite(LED1, LOW);
  }
}
void blinkLed() {

  if (a==0) {
  a=1;
  //ledState = !ledState;
  digitalWrite(LED_interrupt, HIGH);
  delay(100);
  //digitalWrite(LED1, LOW);
  }
  else {
  a=0;
  //ledState = !ledState;
  digitalWrite(LED_interrupt, LOW);
  delay(100);
  //digitalWrite(LED1, LOW); 
  }

  //ledState = !ledState;
  //digitalWrite(LED_PIN, ledState);
  //digitalWrite(LED1, LOW);
}