#define PIN13 13
volatile bool state;
void setup() 
{
  pinMode(PIN13, OUTPUT);
  Serial.begin (9600);
  TCNT1 = 0;
  OCR1A = 1270;
  TCCR1A = (1 << WGM01);
  TCCR1B = (1 << CS02) | (1<<CS00);
  TIMSK1 = (1 << OCIE0A);
  sei();
}

void loop()
 {
  
}
ISR(TIMER1_COMPA_vect)
{
digitalWrite(PIN13, digitalRead(PIN13)^1);
}