#define LED 19 //Posisi LED
hw_timer_t *timer = NULL;

void IRAM_ATTR onTimer(){
  digitalWrite(LED, !digitalRead(LED)); //High Low LED
}

void setup() {
  pinMode(LED, OUTPUT);
  timer = timerBegin(0, 80, true);
  timerAttachInterrupt(timer, &onTimer, true); //Loop dibagian Flag
  timerAlarmWrite(timer, 1000000, true); // 1 detik
  timerAlarmEnable(timer);
}

void loop() {
  //do nothing
}