@dc42 I see... I was trying to use the default baud rate of the device I communicate with, which is 57600. I tested with 9600 and it seems much better!
Thank you very much! I would never have thought of such a thing...
@dc42 I enabled the pullup resistor for the io0.out pin, (and I found out a bad crimping contact for the X endstop... ^^').
Everthing works fine now. Thank you David.
