Thanks for your quick response PaulS.
Just to make it clear, then I can communicate with the Arduino via USB, and then I need some program on the Arduino to, so to say, interpret the inputs from the PC and transmit the desired signals to the device plugged to its outputs, right?
That is, the whole thing works with Arduino connected to the PC at all moments (that was my main question, I do not want to program the Arduino and then use it unplugged from the computer because the SW is too complex for embedding it into the board)
Thanks again,
Matt