#define LED_PIN 26
#define BUTTON_PIN 27
#define V_PIN 4

hw_timer_t * timerled = NULL;

double t;
volatile int cont;
volatile bool timer_on;

IRAM_ATTR void changeState()
{
  timer_on = true;
  cont++;
}


IRAM_ATTR void ISRled()
{
  timerStart(timerled);
}

void setup() {
  t=0.0;
  cont = 0;
  timer_on = false;
  timerled = timerBegin(1000000);
  timerAttachInterrupt (timerled, &changeState);
  timerAlarm(timerled, 250000, true, 0);
  timerStop(timerled);
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), ISRled, RISING);
}

void loop() {
  double frecuencia = 1/((millis()-t)/1e3);
  Serial.print("Frecuencia: ");
  Serial.println(frecuencia);
  Serial.println(analogRead(V_PIN));
  if(timer_on)
  {
    if(cont <10){
      digitalWrite(LED_PIN, !digitalRead(LED_PIN));
    }
    if(cont == 10)
    {
      cont = 0;
      timerStop(timerled);
      digitalWrite(LED_PIN, !digitalRead(LED_PIN));
    }
    timer_on = false;
  }
  t=millis();
  delay(50); // this speeds up the simulation
}