I have a ton of 16c72, older part and yes 5v. Got a couple of these xbees and like I say, using a separate 3.3v regulator for them. Ok, was hoping that I could do a straight shot (in some cases it's worked before) but I'll take your word for it. The plan is to have a xmt/rcv pair with a pic in each box -- so I'll use serin on one and serout on the other. I may try a direct connection first just for the heck of it -- you would think a swing of 0 to 3.3v would be good enough for a logic low, logic high for the serin, my pcb is cramped might have to use a transistor instead of a chip gate. Certainly a resistor on the pic serout would be needed. Thanks.