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Buffered DO Question - when to update...

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Hi all,

 

I haven't done any buffered DO on a multifunction card with DAQmx (I think I did some A LONG TIME AGO on traditional DAQ).

I have to generate a set of 4 PWM signals, controlling phase, DC, etc.  Kinda like a set of stepper control signals, but just different enough that I can't actually use a stepper driver.

 

In general, I will be generating a pattern and then repeating that pattern constantly, either for a number of data points or indefinitely.

Every so often, I will need to change the pattern on user demand, but when I do there will be one "frame" of buffer sent with the transition data, and then I will be sending a different, but repeated pattern constantly.

So let's say I have 10K point "patterns" defined...

 

AAAAAAAAAABCCCCCCCDAAAAAAAAAABCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCDAA

 

1) Would I need to constantly regenerate and feed the buffer with those repeating patterns?

2) Is there some way to have the card repeatedly write the last patter?  Say I define the buffer as 20k points, and tell it that if there is no new buffer, just repeat the last 10k points of the buffer?  Sort of a self-feed of that last 10k?  And then when I send new data, it finishes buffering out the current 10k buffer before it moves on to the new data?

Thanks!


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