Hey Jim,
Error code 7 for the Serial Port Read VI (make sure they are the compatibility VIs) usually means that there has been a timeout. Have you tried perform a loopback test to see if there are bytes at port and then tried to read that data back? It would be helpful if you could post some code so I can take a look at the fault communication. See if you can create a Serial only application and get it working, and if not, post it here.
Thanks!
Andy F.
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National Instruments