How to time AO one one PXI board using clock of another?

[stevempotter]

I am trying to do analog output from a PXI-6733 in one slot of a PXI chassis, that needs to be perfectly synchronized with analog input on another board (PXI-6115). I would like to use the 6115's 20MHz timebase for the 6733's counter, which I use to make the AO retriggerable.

(See attached VI). I have used the Connect Terminals VI to connect the 6115's 20MHz timebase to the 6115's Trig4 line. Then I expect to use the 6733's Trig4 line (which is the same as the 6115's, right?) as the Clock Source for the 6733's counter. This gives the following error:

"Sample mode is set to a value other than Hardware Timed Single Point. This is the only value supported for counter generations when Sample Timing is set to Sample Clock. Change the Sample Mode or the Sample Timing Type."

I am sure there is some easy way to use one board's clock for another board's counter, right? How should I do that?

Thanks,

Steve Potter

[Drewski]

I can't see the code you posted, we're not at version 9.0 yet... someday.  Anyway, LabVIEW has examples, look under...

Examples->Hardware Input and Output->DAQmx->Synchronization->Multi-Device->Multi-Device Sync-AI and AO-Shared Timebase & Trig DSA.vi

There are other examples up there.

One detail that could also mess up things is that the 18 slot PXI chassis have 3 "sections" for sharing signals amongst cards. So if one card is in one section and the other card is in another section, they can't be linked as there isn't signal sharing across sections.

Good Luck!

[tbob]

You need to use the Expost Signal function found in the palette Measurement IO - DAQmx - Task Config/Ctrl - DAQmx Signals - Export Signal.  It will send whatever signal you choose to whatever pin you choose.  In this case, select Sample Clock as the signal and select your PXI Trigger bus as your output terminal.  BTW, you do not need the flat sequence structure at all, not even the little one inside the big one.  Your execution flow is defined by the wires, especially the error wires.

[Mcdan]

Hi Steve,

I'm couldn't tell from your VI what your 6115 was doing, so I'm going to guess that you were unable to share it's sample clock with your AO device directly.  This would be them most straight forward way to synchronize these two devices, however may not be possible if your 6115 is not doing a similar finite retriggered acquisition.  I will assume it is not, since you are using an alternate means of synchronization.

The issue you have here is that you are attempting to use the PXI_TRIG4 line as a sample clock source instead of the counter's timebase source.  In this case, you'll want to set the DAQmx Timing VI for Implicit Timing, and then use the DAQmx Channel Property node to set the DAQmxChannel->Counter Output->General Properties->Counter Timebase->Source property to be PXI_TRIG4.  With this setup, the counter should use the signal on PXI_TRIG4 as the timing source for the counter.  Using this source, it should output a pulse train with the specified frequency and duty cycle.

Let me know if I've misunderstood what you're attempting to do here.

Hope that helps,

Dan