Releasing control of Remote Panel generates Error 1 at property nodes

[Puchkov]

Might be worth taking a look at the following whitepaper:

Error 1 When Setting Front Panel Window Bounds

http://digital.ni.com/public.nsf/allkb/4844BA74383CAD5C86256FAA0059AEE1

[clementw]

Hello Puchkov,

thanks for your reply.

I can't see how the whitepaper you posted is related to my problem. I'm hitting errors on Property Nodes when gaining/releasing control of a VI via LabVIEW's Remote Panel capability.

However, i've elaborated the problem and now it seems like I don't just get Error 1, but also Error 1055: "Object reference is invalid" repeatedly. This happens when _gaining_ the control of the VI, contrary to OP's original description. If it happens, the Property Nodes in the while-loop of my last example generate Error 1055 endlessly and the GUI on the remote side won't be updated (the LED won't blink/flicker). Here, the solution of just clearing the error, as suggested in this thread, is not helping, because my GUI on the remote side won't update at all.

It seems like random whether I'm hitting Error 1 or Error 1055 or an error at all. Sometimes I have to gain and release control for only one or two times to hit an error, sometimes it takes 10 or more tries.

In conclusion, I don't think this is intended behaviour and would be very glad if someone could guide me on how to use the combination of Property Nodes + Remote Panels in LabVIEW.

[Craig_]

The original CAR filed for this was #51463 back in 2007, and the reasons in this thread for it are still valid.

When a client connects and disconnects it is not expected that VI server references stay valid.

Instead of passing references statically into a SubVI I recommend accessing the references in an FGV that you can update if needed.

The Main VI can monitor the two properties previously mentioned in this thread (Wait For Front Panel Activity Function and Remote Panel:Client Connections Method) to keep the FGV populated with the correct references.

To address the error pop ups you should connect the error terminals and/or disable automatic error handling for the subVI.

Does this provide a solution for you?

[clementw]

Hello Craig,

thanks for having a look at my problem.

I will check tomorrow/in the next days whether the suggested method provides a solution to my problem and report back the results.

Best Regards,

Clemens W.

[clementw]

I am still unsure how to solve this issue, so I am trying step by step.

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Craig_ wrote:
When a client connects and disconnects it is not expected that VI server references stay valid.

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By connecting and disconnecting you mean gaining and releasing control of a VI? The errors already occur when gaining/releasing control.

As a user, I would not regard this behaviour as expected. For me, a Reference is just an indirect link to the corresponding Element, which I can access using Property Nodes. The Remote Panel functionality should not change this pattern, in my opinion. Also, the Help on References and Property Nodes does not state any restrictions regarding Remote Panels.

But maybe this is just me and I missed some conceptual parts about References.

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Craig_ wrote:
Instead of passing references statically into a SubVI I recommend accessing the references in an FGV that you can update if needed.

---

The actual References are changing when gaining/releasing control and I have to track the change and store them in a Functional Global to access them in my Sub VI. Can you guide me on how to obtain the changed References? I had a look at Wait For Front Panel Activity Function and Remote Panel:Client Connections Method but those only give me general information about whether a Front Panel Activity occured or general information about the connected clients, number of clients etc.

Thanks for any help in advance and Best Regards,

Clemens W.

[Craig_]

A simple method may be to run a loop in the main VI that just passes the control references into the FGV:

The SubVIs can access the references with a get command.

I would recommend making a cluster of all the references and putting it in a typedef to simplify future updates. 

[clementw]

Thanks for the fast reply and sorry for the late response (time difference :D)

I tested your method and first of all I wanted to see whether the References actually change in the while loop. I wired them to a Variant Indicator but the Refnum stayed the same the whole time, even if I gain/release control of the Remote Panel.

I captured it on video:

http://youtu.be/TKngF4NGDjQ

(Also, in the video, you can see how after some tries of gaining/releasing control I hit the recurring error 1055 and the Sub VI stops working (LED not updated))

If I continue and wire the References to a FGV, this won't be updated, as the Refnums don't change. Is there another way to obtain the changed References?

Best Regards,

Clemens W.

Main VI:

Sub VI:

[Craig_]

Aha, now I can see the same errors as you. Thanks for the videos and the description of what is going on.

I have updated CAR 462394 with these notes and have submitted it to R&D.

[clementw]

Nice! Thank you very much for having a look at it yet again and the submit.

Best Regards,

Clemens W.

[clementw]

Hello Craig,

are there already any updates on CAR 462394?

Mainly I am interested in whether R&D has confirmed the issue and if it's being worked on.

Also, can you/R&D give an estimate on when there will be a possible release fixing the issue?

Best Regards,

Clemens W.