#define PPS_PIN   22
#define OUT_PIN   21

volatile unsigned long pps_seconds = 0;
volatile unsigned long last_pps_millis = 0;
volatile bool pps_event = false;
volatile bool gpio21_event = false;

void IRAM_ATTR pps_isr() {
  pps_seconds++;
  last_pps_millis = millis();
  pps_event = true;
}

void IRAM_ATTR gpio21_isr() {
  gpio21_event = true;
}

void setup() {
  Serial.begin(115200);

  pinMode(PPS_PIN, INPUT);
  pinMode(OUT_PIN, INPUT);

  attachInterrupt(digitalPinToInterrupt(PPS_PIN), pps_isr, RISING);
  attachInterrupt(digitalPinToInterrupt(OUT_PIN), gpio21_isr, RISING);
}

void loop() {
  static unsigned long seconds_snapshot;
  static unsigned long millis_snapshot;

  if (gpio21_event) {
    noInterrupts();
    seconds_snapshot = pps_seconds;
    millis_snapshot = millis() - last_pps_millis;
    gpio21_event = false;
    interrupts();

    Serial.print("Tiempo transcurrido: ");
    Serial.print(seconds_snapshot);
    Serial.print(" s ");
    Serial.print(millis_snapshot);
    Serial.println(" ms");
  }
}