"waveform length increment" pxi 6561

[Timothy 123]

We have a pxi 6561 in our lab for use in testing ics. I want to write a waveform to it using the digital waveform editor and save it as an .hws file. If I write a file that contains the 3 samples, and run my labview program which reads this file and then generates the waveform, I get an error saying that 3 samples is not an integer of the "waveform length increment" which is four. Is there a way I can change the waveform length increment?

[Ryan_M]

Timothy,

Thanks for the post.  The way the 6562's memory is partitioned, you are limited to using waveforms that are an integer multiple of 4 in length.  The easiest way for you to fix this may be to reopen your waveform in the NI Digital Waveform Editor and add the extra sample at the end.  If this is not possible then depending on how you read your data from the HWS file, you can append the extra sample using LabVIEW. 

If you read the data as an array of U32, then you can easily use any of the array functions built into LabVIEW to add an additional sample to the array.  If you read the data as a Digital Waveform Datatype (DWDT) then you will need to use one of the functions from the  Programming>>Waveform>>Digital Waveform palette.  The "Append Digital Samples.vi" may be suitable for this function.

I hope this helps.

[Timothy 123]

Does anyone know if when writing a script and generating a subset of those waveforms, does the subset have to be an integer mutiple of the waveform length increment.

[Yardov]

Hello Tim,

This is going to be the same case. Any waveform you output needs to be multimple of the wavefor lenght increment (4).
This is like the minimum packet size.
Good luck,

Yardov

[Timothy 123]

Thank you for your reply

I have many waveforms that are all quite similar except at a certain subset. Is there a way I can concatenate the waveforms say generate a subset of A, generate a subset of B and generate a subset of C, and combine these into one waveform and then send it off to the device and just make sure that the concatenated waveform has the correct waveform lenth increments.

[kirsch]

Absolutely! That's one of the reasons Script Mode is so powerful.
You can download waveforms A, B, and C to the device. Then in your script, you can generate any subsets of any waveform in any order (as long as each subset has the right size - a multiple of 4 sample in this case).

Marcos

Message Edited by kirsch on 10-16-2006 09:03 AM

[Timothy 123]

Hi,

Just to make sure this is correct, you had said that each subset of the waveform has to have a waveform length increment of 4. What if they have waveform increments 3, 4, and 5, which adds up to 12 and is a multiple of 4. Will it work in that case when I contatenate the waveform subsets into a waveform of 12 samples.

[garretth]

Hey Tim,

That's right. Each subset has to be a multiple of four. You cannot have several subsets that simply add to 12 (or any other multiple of 4). The hardware requires that each different subset have at least four samples and that it be a multiple of four.