MAX and VISA displays extra COM port

[Vanessa]

From the Windows 2000 -> Control Panel -> System, it displayed that there are the following ports:
COM1 - Serial port
LPT1 - Parallel port
COM2 - USB-to-serial port

However, when checked with MAX & VISA, it displays an extra port:

ASRL1:INSTR (COM1)
ASRL2:INSTR (COM2)
ASRL3:INSTR (COM3)
ASRL10:INSTR (LPT1)

I don't know where does the COM3 comes from, or how to eliminate it. I have tried to take out the reference to COM3 on the visaconf.ini , but it reappears.

At the same time, I am having Labview crashes problem (access violation) after I communicate with the instrument connected via COM2 (Labview.exe crashes on a 2nd run of the same script, which needs restarting of computer before it will work again, for one r
un and crash again on the 2nd run). Does this problem has anything to do with the appearance of COM3?

Please help!

Thanks

Vanessa

[Dan_Mondrik]

Vanessa:

I believe COM3 is still in your registry under HKLM\HARDWARE\DEVICEMAP\SERIALCOMM. It is possible that it existed at one time previously and the system never deleted it (although this seems odd to me). You should be able to run regedit, find this key, and delete the COM3 string item in the right hand view.

Even though viFindRsrc is returning COM3, I do not believe that viOpen will succeed - it should return an error for that port since you say it does not really exist. In fact, MAX should show some kind of exclamation point or X through the icon. Does it do this?

Regardless of the MAX behavior, this should not affect your LabVIEW program in any way. I have no idea what is causing your crash but it is probably not related to this phanto
m COM3. If you think the crash is in VISA, I suggest you use NI Spy and enable Log to File with Fail Safe Logging selected. Then after the crash you can load the .spy file and see if any VISA call did not return.

Dan Mondrik
Senior Software Engineer, NI-VISA
National Instruments