Quick question, NULL modem or straight RS232 for Onkyo receiver? I haven't done a lot with ended cables and I am not sure it matters anymore. Did the ports get "smart" like Ethernet or stay dumb.
I think that question will be answered by looking at the type of the RS-232 connector on the receiver.
If it is male, than it is null modem cable, if it is female you have to have straight cable.
Regards
Thanks for the responses, especially the link. I am past that part of my project with much success. Here is my simple tkinter gui python program for serial control of Onkyo;
I included a com port monitor for debugging.