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Using Digital-In to trigger AI capture

I am  using an M series (6229) capture a Digital Input (not a PFI) and an Analog Input. I would like to have the Analog Input triggered on the falling edge of the Digital Input. I would also like to have a capture of both the Digital In as well as the Analog In for a total of 2 seconds (maybe an extra 100ms if I can specify the samples before trigger). Has anyone done this before? Are there notes on whether this can be done or not?

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Hello Carlos_Juan,


Before we discuss how this can be achieved, I would like a little more clarification on your set-up. This is what I think you're trying to achieve:


You have a Digital Input task and an Analog Input task running on your USB-6229.  Your digital task is not on a PFI line.  You would like the Digital Input to also act as the trigger, correct?  


Do you have any PFI lines available?  The reason I am asking this is that you will need to wire the signal of the Digital Input line to one of the PFI lines for triggering.  You can find more information on that in the M series User Manual located here:


I would also highly recommend taking a look at the Voltage - Continuous Example in LabVIEW (can be found in Help>>Find Examples>>Hardware Input and Output>>DAQmx>>Analog Input>>Voltage - Finite


For the pre-trigger data aspect of your problem, I would recommend reading about Reference Triggering.  This Whitepaper Article can prove to be useful here, more specifically the section on Pretriggered Acquisition on a Digital Reference Trigger:


Hope this helps!



Nadine H.
Applications Engineer
National Instruments
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