int pinA = 32;
volatile int contador = 0;
unsigned long previousMillis = 0;
long interval = 1000;

void setup () {
pinMode (pinA, INPUT) ;
Serial.begin (115200);
attachInterrupt (pinA, interrupcion, RISING); //Flanco subida 
}
void loop () {
unsigned long currentMillis = millis ();
  if ((currentMillis - previousMillis) >= interval){
    previousMillis = currentMillis;
    Serial.print("pulsos/seg: ");
    Serial.println (contador) ;
    contador = 0;
  }
}
void interrupcion() {
contador++;
}