int ledPins[4] = { 25, 26, 27, 14 };

void setup() {
  Serial.begin(115200);
  for (int ledPin : ledPins) {
    pinMode(ledPin, OUTPUT);
  }
}

void loop() {
delay(10);
check_terminal();

  //led 4 knippert 4x/minuut
  static unsigned long timestamp = 0;
  static bool led_aan = 0;
  if (millis() - timestamp > 1500) {
    timestamp = millis();
    led_aan = !led_aan;
    // Serial.println(led_aan);Serial.println(timestamp);
    digitalWrite(ledPins[3], led_aan);
  }
  // einde led 4
}