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

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

      updateLED();
    }
  }
}

bool equal(String str1, String str2) {
  return str1.compareTo(str2)==0;
}

// limitation of brightness
