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Analog trigger for digital output task

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Hi all,


I'm using DAQmx on PCIe-6363 (LabView 2017).

I'm trying to uderstand why my digital output tasks become irresponsive as soon as I set an analog trigger.


The corresponding hardware is shown in the picture: I need to use the AI level to trigger a counter task, but by reading several posts here I understood that this is possible only by triggering the CO with a digital channel itself triggered by the AI (APFI0 ==> DO ==> PFI ==> CO) .


What happens is that the DO task doesn't activate when the analog trigger is set, be it type level or window, or APFI0/APFI1, and no matter which values I choose as thresholds.


To check what is happening I'm using the example VIs: continuous digital input (CDI), continuous digital output (CDO) and continuous analog output (CAO).

I only made the least amount of changes (added an offset to the CAO sine wave, changed the CDO trigger to analog edge or window, set the CDO to write digital waveforms instead of port patterns), that you can find attached.


In this case, too, the digital output doesn't activate.

Do you have any suggestion on how to solve/investigate this issue?

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Accepted by Migeh

I don't think I've ever tried to *directly* trigger a digital or counter task based on an analog trigger wired into a special APFI terminal.  I wouldn't have expected it to be supported.


What I *have* done is to create an analog-triggered AI task, even if it's just a dummy task where I don't care about the data.  With the AI task in place, I can then make use of internal signals such as "/Dev1/ai/StartTrigger" or "/Dev1/AnalogComparisonEvent".  Depending on your needs, one or both might work for you.   Either can be used as the trigger source for your other tasks.


You may need to right-click the terminal constant (or control), select "I/O Name Filtering...", then check the box to "Include Advanced Terminals" to locate those particular internal signals.



-Kevin P

Message 2 of 3

...and indeed, it works. At least with the "/Dev1/ai/StartTrigger".


I initially tried to use the APFI terminals as analog triggers for the AI channel, but no results.

Using the channel as its own trig source instead worked.


I think I'm not really understanding what these APFI terminals actually do. I will need to study more.


Thank you!


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