It's been a while now since I had to correlate samples between a regular DAQmx card and a DSA card, but I recall several gotchas while doing it.
1. The DSA has a more restrictive set of available sample frequencies. Life is a bit easier if you let it be the timing master and let the DAQmx card be the timing slave.
2. My DSA card (and thus maybe yours too?) had a non-negotiable but significant delay from the time a signal edge occurred at the physical pin and the time it was stored in the data acq buffer.
3. I think I recall a DSA task property available that could export a signal analagous to a sample clock. I think it had a different name though, probably to avoid ambiguity due to the way the sigma-delta A-to-D converters work. The point is, try to use this to drive your DAQmx task with this signal, using it as an external sample clock. Just be sure to configure the DAQmx task with an approximately correct rate for that external signal.
4. There's still a lurking issue after all this hardware clock synchroniczation. The delay inherent in the DSA. At the moment the exported clock-like signal is asserted, both the DSA and the DAQmx tasks will store a sample in their respective data acq buffers. What's stored in the DAQmx buffer is what was happening at that same moment. What's in the DSA buffer is what happened a little while ago, due to the signal delay.
Just be aware so you can figure out how you'd like to compensate.
-Kevin P
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