hi, when I want to communicate with Arduino IDE via PD I newly get the errormessage:

error: [comport]: could not open device COM4:
failure(5) ERROR_ACCESS_DENIED

Can anyone tell me how to fix this?

(transfer between analog in and arduino ide is working)

@Val If COM4 is the port you were successfully monitoring in the Arduino IDE using Serial Monitor, then I wonder if you've tried exiting the Arduino IDE before running your Pd patch?

Edit: Assuming my hunch is correct, I ran some tests and you only need to exit the serial monitor, not the whole IDE

Yes that was it .. thanks a lot!