@marceltrapman when you change the BAUD rate setting in the source/config file to something lower/other you can also use 3.3V Arduinos as (Serial)Gateway. Of cause your controller needs also to be told about the lower BAUD rate. Check out http://wormfood.net/avrbaudcalc.php?postbitrate=9600&postclock=8 for an overview of Clockspeeds (usually 8MHz for 3.3V and 16MHz for 5V types) and coresponding BAUD rates.