Error -1074130544 occurred at niScope Multi Fetch WDT.vi:5730005

[Punsach]

Hey guys,

So I have this program here that deals with pulse signals which are being received from a PXI-5122 digitizer. But I keep getting the above error with the possible reason of the session handle is not valid. Any idea of what could be wrong?

[Wayne_T]

Punsach,

Error -1074130544 should be taken literally.  Is the device name in MAX the same as in your code?  It could also be the device is reserved/not available by the next time the device is being accessed.  I recommend testing the device by running one of the shipping examples provided in LabVIEW.  They are found at Help >> Find Examples... and navigate to Hardware Input and Output >> Modular Instruments >> NI-SCOPE (High-Speed Digitizers) >> Continuous Acquisition >> niScope EX Fetch Forever.vi or any of the examples you prefer.  Point to your device and see what happens.  If you get the same error, check MAX for device information.  This will narrow down where to look to next for troubleshooting.

[Nathan-P]

I believe this error is occuring because of your use of several IN-SCOPE Express VI's, and how your code is implemnted, attempting to use several of them at the same time.  The NI-SCOPE driver can only have one valid session reference to hardware at any one given moment.

It appears that your code has reached the point in complexity, that you need to move away from using Express VIs and start using the fully fledged NI-SCOPE API.  There are many examples using it that can be found in the Example Finder. 

I hope this helps!

[Punsach]

Is it possible to use one NI SCOPE API to access multiple channels and devices? 

[Nathan-P]

Yes, you can use the NI-SCOPE API to access multiple digitizers/channels, but you will have to handle the Sessions for each device separetly.  An niScope session can only represent one device, so if you have two devices you want to control, you will have to manage two different niScope session references, which correspond to each device.

What are you trying to do?  Depending on what you are doing, there is also some advanced syncronization tools available to have all the digitizers work in parallel.

[Nathan-P]

If your interesting in some examples of using the niScope API with multiple devices, use the LabVIEW Example finder and look at these examples:

• niScope EX Multi-Device Configured Acquisition (TClk).vi
• niScope EX Multi-Device Different Sample Clock Rates (TClk).vi

[Punsach]

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Nathan-P wrote:

What are you trying to do?  Depending on what you are doing, there is also some advanced syncronization tools available to have all the digitizers work in parallel.

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Basically what I am doing is taking in pulse signals from two NI PXI 5122 digitizers, and generating them on 4 different waveform graphs. The user should be able to tell the program which channels/devices are active and which ones should not be used. The graph then has 4 cursors, and the user places them so that all the points between them are averaged and one average is subtracrted from the other. A moving average is performed on these differences (a pulse signal is generated 1 per millisecond) and then they are all put in one waveform chart. I used a producer/consumer structure to perform this task. 

[Punsach]

there an example that can help me use NI SCOPE by working with only the signal sent to the waveform graph?

[Nathan-P]

Using the LabVIEW Example finder, there are loads of examples that illustrate how to use the NI-SCOPE API.  The most useful to you perhaps would be "niScope EX Configured Acquisition.vi".  This is a good starting point, for most applications.

Also, I had no idea what all your design goals are, so I just re-wrote your code in a better architecure, which also isn't great, but I think it recreates the behavior you did in your code, though is implemented slightly differently.  The code is broken, and you will need to fix your sub-VI (you didn't post it), to use the new data type.

I hope this helps.