Instrument Control (GPIB, Serial, VISA, IVI)
maximum usb com ports exceeded
Good First Day of Fall (in the northern hemisphere)!
I've run into a problem that I anticipated a few months ago but didn't have the time to deal with then. We are testing a product we manufactuer here that uses a built in USB to serial converter. What happens is that each time a new unit to test is plugged Windows (XT) looks at the serial number of the unit to see if it has been plugged in before, and if not it issues it a ComPort number, incremented from the last one. Unfortunately, while Windows will merrily keep incrementing the number, VISA serial is limited to 256 com ports, and we are up to 259 now (they tried with a few after getting the first failure). I have seen at least one location in the Registry where the serial number to com port info is stored, but am reluctant to start stomping around in the Registry without knowing where else to look as well. I noticed where it had 259 entries with VID# and serial numbers, and found at least one place else where "Com259" was in the registry but don't know where else to look. I have tried not to play too much in the Registry, a program that had to change com port settings to change port settings from RS232 to RS485 being the sole exception. "Things" that happened then during that development have made me reluctant to venture back in. I did make a backup ("Export" of the current registry, but when I tried deleting the latest entry (the one for the current device sernum) it wouldn't let me and I decided to ask others, and so here I am!
Thanks,
