Synchronization of a vi to pxi_trig

[xl600]

With a PXIe-8135RT and a PXI-6281, how can I pause a VI until a PXI_Trig line changes state?  I want to trigger a VI based on a PXI trigger.  I know how to trigger a 6281 task but it's confusing how to synchronize a VI to the same trigger source.

Thanks,

XL600

[Norbert_B]

XL600,

what is the purpose of this triggering? Except for data analysis, i cannot think of a real use-case of this for now. And data analysis is easy as triggered read commands already do what you are looking for.....

Norbert

[xl600]

The use?  My pxi controller needs to simultaneously sample multiple streams of in and out UDP packet streams and do so using a start trigger common to my DAQ cards and fpga cards.  The sync comes from an external or internal (selectable) source.

So, I need to start and stop my network data capture vi's based on the same trigger those other hardware cards are using.  The sync doesn't have to be terribly accurate, but it does need to be within a few hundred microseconds which should be entirely feasible in labview realtime.

The sync between the fpgas and ananog cards needs to be much better than that, which was is why I am using the trig bus.

Something I've wanted to ask about the boards here... Why is it often the case that the first response is to question the validity of the underlying reasons for the question rather than addressing the question itself?  It's not that this kind of initial of response isn't sometimes useful, but it's a bit annoying.

[Norbert_B]

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@xl600 wrote:
[...]

Something I've wanted to ask about the boards here... Why is it often the case that the first response is to question the validity of the underlying reasons for the question rather than addressing the question itself?  It's not that this kind of initial of response isn't sometimes useful, but it's a bit annoying.

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It's simply by experience. Just to give a stupid example:

I ask you how to carpenter a square using four wooden needles. It's good if you give a direct answer, but you might also ask why i need a wooden square. Would it still make sense to instruct me on carpenting that thing if i would reply: I want to attach this to a soap box for a soap box derby so the soap box can move (read: as a wheel)!

That being said, to answer your question:

You can register DAQmx tasks as event source using "Register Event" (DAQmx palette >> Advanced >> DAQmx Events). Point is that there is no "trigger occurred" event. But you might be able to workaround by triggering a counter output (dummy) task which triggers that event. I think this could work for you....

Norbert

[xl600]

Thanks, I'll give that a try.  My cards are 6281's so I'll have to look into if those would support DAQmx events like that.

[xl600]

I managed to get things working using your suggestion, but then I realized that the DAQmx Create Timing Source.vi can do what I need directly using a timed loop.

The sent notifier thus becomes a pretty good software sync to the PXI trigger.