Why I get error -1073807339 when accessing serial port (VISA)? Software has worked many years and suddenly not anymore. Can it be hardware problem? Or can some updates in the computer cause this problem?
I would suspect a hardware problem first. A timeout err means you are not receiving any data. Check the connection with Hyperterminal to verify that it's not a software problem but then look at the cable and then perform a loopback test on the port.
