NI-FGEN Problems in TestStand using IVI Calls

Question

Hello:
I have a problem. When using a 5411 under TesStand, making IVI calls the 5411 O/P is distorted when I configure it to O/P a simple Waveform ( 1.544 MHz, 5Vp-p 0V DC Offset). The same setup using either a CVI application utilizing the function panel or the soft front panel yields a fantastic O/P. If I can not make IVI calls from TestStand then what is the use?
Help.... Very fruntrared and on a deadline
cheers...

Answer 1

Hello Craig -
I've quickly looked over the CVI IVIclass demos including the quick bit of Fgen code, if you run this project and monitor the output in MAX you are seeing good results? If so, yes I'd check the settings in your IVI steps in TestStand. (If you haven't seen it yet try \CVI\samples\iviclass\fgen.prj)
CVI also ships with function-by-function class help files which on my machine are located at C:\vxipnp\winnt\niivi\Help, I point this out since the demo sequence for IVI in TestStand makes a direct DLL call to set up the soft front panel as a non-interactive window... there are a few other cases where features of the driver are not accessible just by editing the step properties, but that is across the board, so again if it worked in CVI it should work here.
I'm going to attach a quick little TestStand sequence (written for TS 2.0.1f1 the current release) to this project as a way of you just loosely troubleshooting, all it will do is launch the soft front panel and use the controls to try and set up your waveform... Try it once with the simulated instrument, or just go straight to altering the FileGlobal variable to point to your logical name and tell me if you get better or worse response?
To alter the internals of the call to hardware right-click on the second step and choose 'edit Fgen'... you may want to examine your clock, the channel settings and extensions to make sure anything you configured in your code is configured here... The only thing I am still unsure of is whether you were using the default sine waves or if you were definining something arbritrary, the 5411 does have the ability to set sample counts/ waveform size /sampling rate. You may want to try setting your Arb SampleRate higher, or fall back on a quick DLL call to set some attributes manually if you can't access them any other way.
You can use the IVI operation "get Information" on a particular logical name to aquire the current/default settings of your instrument.
Below is some text I extracted from a LabVIEW example (I don't know how useful the actual code will be, but perhaps this is the cause of your undersampled data?) Jitter can also be a symptom of undersampling. I will try and check with the hardware team for you and post if I have any other ideas...
-Regards
Elaine R.
National Instruments
http://www.ni.com/ask
--Extracted from an example "Generating Segments of Larger Waveforms with the NI 5411" --
>>To set up sample counts, pass the array of sample counts you want to use to create a new arbitrary sequence. The array must have at least as many elements as the value you specify in the Sequence Length parameter. Each Sample Counts array element corresponds to a Waveform Handles array element and indicates how many samples of the given waveform to generate. Each element of the Sample Count array must be larger then the minimum waveform size and a multiple of the waveform quantum. You can obtain these values by calling niFgenQueryArbWfmCapabilities.
For the NI 5411, you can use a minimum of 256 Sample Counts, with a quantum of 8, which is the same as creating a waveform for the NI 5411. The other restriction is that you cannot use a number greater than the number of samples in the waveform.
In terms of use, the NI 5411 only generates the number of samples that are indicated by the Sample Count number regardless of how many actual samples are in the waveform array downloaded to the NI 5411.
Attachments:
fgen.seq ‏50 KB