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