DMA host to target synchronization

[Peter1111]

I am using two host to target DMAs to generate two arbitrary waveforms to be output on anAO module.  I want these waveforms to be output at the same time, but it appears as if one of the waveforms leads the other by several micorseconds.  The two waveforms are in two separate arrays, passed to the DMA.  It appears as if the lag is on the host side.  I've attempted using the timing loop with the synchronization vi and adjusting the offset of the timed loops, but that seems to increase the delay more, or have not effect.  Is there a way to get these DMAs to start passing the data at the same time? 

[Andrew_E]

Hi Peter,

Good question. I am thinking that this may be possible using occurrences. Just before we want to write to one of the fifo's set the occurance so that the second fifo could write as well. However this may still cause a lag. As of yet there is no way to purely trigger Fifos. If they are in the same loop they should happen relatively at the same time. I will try to use occurances tomorrow, time it and see if they come back synchronously.

[Spectre_Dave · Accepted solution]

Peter

What you can do is pack the two waveforms into one DMA and parse then at the AO.

AO's typically use I16s to represent the waveform data and the DMA bus is U32. 

Use the join number to combine the two waveforms, then DMA the composit signal, then at  the AO use split numbers.

I have used this succesfully with good results.

[Peter1111]

Thanks, the "DMA stuffing" did the job.