#define RED_LED 9

volatile boolean state = HIGH;

void int_ledact();
int a = 1;
float b = 0.00;

void setup(){

  pinMode(RED_LED, OUTPUT);
  attachInterrupt(0,int_ledact,FALLING);
  Serial.begin(9600);

}

void loop(){

Serial.println(a);
delay(300);
a++;

}

void int_ledact(){
  Serial.println("interrupt");
}