         Serial.println(argument);
       }
     }
-    else if(equal(command,"position")) { // set position
+    else if(command=="p") { // set position
       // TODO argument check
       // argument is float
       slit_position = argument.toFloat();

    String command = Serial.readStringUntil(':');
    String argument = Serial.readStringUntil(';');
    
    if(equal(command,"instrument")) { // set instrument color
      Serial.println(command);
      if(argument.length()==11) {
        // argument likes "255.255.255"

      Serial.println(slit_position);
      updateLED();
    }
    else if(command=="b") { // set brightness min value
      // TODO argument check
      // argument is float
      brightness_min = argument.toFloat();
