Instrument Control (GPIB, Serial, VISA, IVI)

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NI VISA Doesn't Match Windows Device Manager

I am attempting to communicate with a communications device class (CDC) USB Device.  NI VISA is displaying COM ports that don't exist.


Windows Device Manager displays two COM ports: COM3 and COM4.  These are correct.  NI VISA in LabVIEW displays: COM3, COM4, and COM4).  Sometimes VISA will show ASRL5 and ASRL6 as well.  This does not match what shows up in Windows Device Manager.  How the hell are the COM ports populated in VISA and why are they wrong!?

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Message 1 of 7

First, it would be nice if you were to provide those two images.  I have seen that when running NI VISA, it requires the user to mention which configuration the software should be using (Windows or VISA).  Without that selection, sometimes ports would have dual options until one method or the other is chosen.  If that is the case for your configuration, then nothing is wrong as it requires user intervention in NI-MAX to select the preferred connection option.

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Message 2 of 7

Here's a side-by-side screenshot




In this case, the device is present in the system and Device Manager correctly shows the device as present.  While VISA resource manager displays the device as 'Not Present'.


The opposite case is also true.  The device will go into standby/sleep and VISA will continue to incorrectly show the device as 'Present'.  While Device Manager removes the device from the list.


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Message 3 of 7

Here's a screenshot of the other case.


COM4 is disconnected and stills shows up in VISA resource manager as present.




I'm not sure where the settings are to pick between Windows and VISA configuration.

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Message 4 of 7

I find that doing [Refresh] in MAX does not update many things while doing [F5] does. Try it.

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Message 5 of 7

Thanks! Yes that worked. I never would have thought to do that.

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Message 6 of 7

Nice work NI, bang-up job! 👍

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Message 7 of 7