Applications, development tools, FPGA, C, WEB
#7736 by tech62
Sat Jul 15, 2017 9:37 am
Hi all,

I'm wishing to generate arb signals to the fast DACs from LabVIEW, but the example code :"custom waveform signal generation". does not seem to work.

When I try the other generate waveform examples , which use the "configure standard waveform.vi"..they work fine...but programs that use the "configure arbitrary waveform.vi" do not give an output.

Does this example vi work for others ?
How long should the input data arrays be ..16384 only ?
How do we set the DAC output rate of this input data ? I guess in the "config standard waveform.vi"
Perhaps this example is missing some essential config vis which would otherwise make it work.

Looking inside the vi shows straightforward SCPI command construction...is there some documentation about what SCPI commands RP handles so I can perhaps write my own vi ?

Any suggestions from people who have it working would be much appreciated.
Ideally I need to input dual long data arrays (16383 say) to both channels, and be able to control the output rate, (to be fast ie: 1 Msps) so I create interesting dual signals...and if they repeated constantly, as does the waveform generation example that would be great.

Its just the same task as for "generate waveform" continuously but with custom data loaded.

Thanks for any tips.
tech62
#7737 by tech62
Sat Jul 15, 2017 11:49 am
Hello again,
I thought I'd take a look at the VIs supplied to see if I could spot some errors..since I suspect it work w MATLAB.
I found that when the data block is transferred in the "config arb waveform.vi" it is terminated with a "," instead of a ";" like the other SCPI transfers.

I edited this vi to replace the last ' with a ; as you can see here:

forum-arb-code-fix.PNG



This seems to help, as you can see below..it is working with the highlighted vis being replace with the modified one..which I labelled MOD ARB to avoid confusion.

forum-arb-code-example.PNG


I've attached the modified vi..its in LV2016.
If you have a diff LV..just do the edits yourself as shown above.

Hopefully this is a useful fix and doesn't cause more issues than it fixes.

One thing Im wondering about though...it takes 15 sec to load and output the new arb signals ? Any reason for this ? Is SCPI really slow ? Ive never used it before. Any insights appreciated.

Cheers,
tech1962
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