int interrupt = 2;
int teller;

volatile unsigned long current_micros;
volatile unsigned long old_micros;

volatile unsigned long current_millis;
volatile unsigned long old_millis;

volatile bool state;

unsigned long time1;
unsigned long rpm;
unsigned long frequentie;
float periode;

void setup() {
  analogWrite(3, 127);
  pinMode(interrupt, INPUT);
  attachInterrupt(digitalPinToInterrupt(interrupt), toerental, RISING);
  Serial.begin(115200);

}

void loop() {
  current_millis = millis();

  if(current_millis - old_millis >= 1000){
    
    frequentie = teller/2;
    rpm = frequentie * 60ul;
    
    
    Serial.print(teller);
    Serial.print(" ");
    Serial.print(frequentie);
    Serial.print(" ");
    Serial.println(rpm);

    old_millis = current_millis;
    teller = 0;
  }

}

void toerental() {

  if(micros() - old_micros > 1000){
    
    old_micros = micros();
    teller++;
    

  }
}