DAQmx Error 200400 - Cause unknown

[Rob Hingle]

I am creating an arbitrary waveform (shaped sinusoid) and had been doing so for quite a while before I first saw this error -200400.  The source is the niFgen create arbitrary waveform vi, and the explaination is that the number of samples is not an integer multiple of the length increment (requested value=13050 waveform length increment=4).  I have no idea what the length increment is; the vi feeds the inputs, none of which are increment, to a dll.  The error code is 1074115985.  I have band-aided the problem by changing my samples per cycle from 512 to 513, but would like to know the real source in case it continues to show up. 
Thank you,
Rob Hingle

[Drew Creel]

In NI-FGEN, the length of an arbitrary waveform must be an even multiple of the waveform length increment, or "waveform quantum".  In most cases this is 4 samples.  You are getting this error because 13050 is not evenly divisible by 4.  To fix this, you can either add two samples to the length (13052 is evenly divisble by 4) or, if you're repeating the waveform many times, simply double the size of the waveform buffer and put two periods of the waveform in the buffer.

Drew Creel
Software Engineer
National Instruments - Signal Generators

[Rob Hingle]

Well it will be easy to pad the arb with extra zeroes but how do I know what the increment will be?  You say most cases it is 4, do you know the conditions for that?
Thanks

[Drew Creel]

You can query the "Waveform Quantum" attribute at any given time to find out what the increment is.  (NIFGEN_ATTR_WAVEFORM_QUANTUM in c/c++)

For current NI-FGEN devices, the increment will always be 4 unless you have a 5441 in complex data processing mode, in which case it will be 2.

Drew Creel
Software Engineer
National Instruments - Signal Generators