Thanks Jerson and Dave for the comments.

There will be times that the computer and GPS will be on different power supplies and at times the same. I've thought of just level shifting the signal and sending it to the pic, but thought since I'm at it might as well isolate the two units. The combined value of the GPS and PC is very pricey. I'll try the appnote Dave provided, looks simple enough even I maybe able to do it.

Additional comments also welcome.....


Thanks again,
Steve