Hi Jan,

Did you upload the new BreakoutFirmata sketch to your Arduino?
https://github.com/soundanalogous/Breakout/tree/master/firmware/BreakoutFirmata

You’ll need either BreakoutFirmata.ino or StandardFirmataPlus.ino to get the Serial functionality. BreakoutFirmata.ino includes support for Stepper motors but is otherwise equivalent to StandardFirmataPlus.ino (not to be confused with StandardFirmata.ino which does not support Serial).

best,

-jeff