Hi Physics, Yes, you do need to close the VISA-Serial port when completed. You may have problems closing it if there is an error that occurs before you get to close it.
Did you verify the serial port configuration setting and make sure they match that of HyperTermial? I am using LV7, so the way to select the COM port is by using a VISA Resource name (ie: COM1). I seem to remember that on previous versions (LV6) that this was done by using a number to set the port. If my memory is still okay, you have to use "0" (zero) for COM1 and "1" (one) for COM2 and so on. That can be a source of error because the numbers are offset by 1. In another thread, someone proposed to look at handshaking. I don;t think it is the problem in your case, but you can look at it too. This is done by using a property node and property "Serial Settings->Serial Flow Control". Check it by reading from the property. Set it by writing to the property. Can you attach your vi? Let us know which version of LabView you are using. -JLV-
