VISA Close hanging

[matys]

Hello!

Does anyone know when VISA Close hangs?

In the attached Pictures, Picture `VISA Close Error01' shows our VI trying to shut down a VISA Session using the VISA Close VI- but VISA Close never exits.

We can reproduce this Error, but it certainly doesn't happen all the time. (Usually there's no problem with the VI shown in the Pictures.)

Anyone has an idea why?

Picture `VISA Close Error02' was added only to show what happens in the other Case o/t Case Structure.

[thols]

What kind of resource are you talking to? 

Have a look at these:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019YYESA2&l=sv-SE

https://forums.ni.com/t5/Instrument-Control-GPIB-Serial/VISA-Close-makes-LV-freeze/td-p/787344?profi...

[matys]

Hey Thols,

we are using 8 Cameras connected to an Acroname USB HUB:

- the Acroname is connected to our Desktop and comes with a LabVIEW Library. We don't suspect any difficulties here.

- the Cameras are connected by USB (2) to the Acroname.

  We use the Silicon Labs driver (https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers) for Serial Communication over USB.

[crossrulz]

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@matys wrote:

we are using 8 Cameras connected to an Acroname USB HUB:

---

My first thought here is Windows USB power management.  Go into the Device Manager and find the power settings for each USB hub you have in there.  There should be an option for a "power saving feature" where Windows will turn off the USB hub/device as it sees fit.  Turn that off.

[matys]

Hello crossrulz,

Thank you for your suggestion!

We tried it- disabling the Power Management of both the Acroname USB-Hub and the connected Cameras.

See the attached Pictures.

Unfortunately, it doesn't seem to make a difference: Some COM-Ports still fail to show in the Device Manager..

[matys]

Hello [anybody?]

Unfortunately we see VISA Close.vi hanging even if the COM-Port shows up in Windows[10] Device Manager.

Have a look at the attached Picture `Visa_Close_hangup' below.

With VISA Close.vi hanging, our whole application (and indeed the LabVIEW Project) is hanging..

Does someone have a suggestion as to why VISA Close won't close?

[jason-cce]

Please refer to the attachment.

Write this way, there is no guarantee which will be executed first.

[matys]

Hello jason-cce

Thanks for your reply.

You're wrong. The Error Wire and the Flat Sequence ensure the VISA Close.vi is executed first.

[matys]

We tried to re-install the VISA Driver and the Silicon Labs Driver (CP210x).

No Difference. 

VISA Close.vi still hangs. See the Picture below.

Let's ask a more general question here:

Does anyone have trouble using VISA to set up Serial Communication between a Desktop Computer (Windows10, x64) and several Devices connected to an USB-HUB, using a Virtual COM Port?