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Trigger from digital input - DAQ acquisition time control issue

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Ignore most of this, but I'll point out the salient parts ...

Trigger AI.png

Here we build the A/D Task, starting with the device (here a USB-6009) coming in on Triax Dev.  At the very top, we build the Trigger Task by adding /PFI0 to the end of the string naming the USB Device.  The stuff in the middle is building the A/D DAQ Task (using linear scale factors, which is why it looks so busy in the middle).  The last two function set the Sample Clock (Finite, 400 samples at 1kHz) and set the Trigger that we defined in the upper Left corner as the A/D Trigger on the Rising Edge.  Now, when a TTL signal comes into the PFI0 input, the A/D will take 400 points at 1kHz.  Trigger in, samples out.  [There are, of course, DAQmx Reads to get the data in so we can use it, but that's another VI].

 

Bob Schor

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Thank you GerdW, i used a shift register and an implies function...crazy that it was a logic fix.  I still need to learn how the DAQmx Trigger VI works, but this will get it done.

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@coolhandLV7 wrote:

Thank you GerdW, i used a shift register and an implies function...crazy that it was a logic fix.  I still need to learn how the DAQmx Trigger VI works, but this will get it done.


What?  I'm not an Engineer, but even I know that when a TTL signal goes from Low to High, you get a Rising Edge, and when it stays High, goes from High to Low, or stays Low, you don't.  So you don't need to do anything except wire the TTL level to the Trigger Input terminal of the A/D and set Trigger to "Rising Edge" (as I showed you in my Snippet) ...  The other thing I learned is "Don't try to replicate in Software what is already fully fleshed out in Hardware" [I just made that up].

 

Bob Schor

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