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NI 9474 digital output timing problem

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Hello all,


I'm trying to output 3 digital signals. I constructed them as square signals inside a loop with a 1kHz resolution (see attached fig). The generated signals are generated correctly, the problem starts when I send them out through the DAQ Assistant. The loop suddenly slows down to about 100Hz and I don't get the correct signals on the output (If DAQ As. is disabled, works fine again).

I'm using cDAQ-9174 and NI 9474. I tried to set it to HW timed but It gives an error (-200077).

I don't have any experience in digital output timing, any help would be really appreciated!


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Accepted by topic author Tomaz79

Hello Tomaž,


You can try setting up your task using the DAQmx functions. Your device is hardware timed , so setting the loop to 1ms won't work, especially on Windows, since Windows can't run loops faster than 10 ms.


You can find out more about DAQmx here. What you need to do is set up a regenerative hardware timed digital output (you can see an example in the attachment).


The DAQ Assistant can do that for you, but you have far less control over your settings. You can read more about DAQ Assistant here.


A great resource for DAQ is this PDF, and of course the NI 9474 manual. Don't forget to set up your power supply on the Vsup and COM ports. That caused me some headaches a couple of days ago 🙂 .


Kind regards,


Best regards,
Rares C.
Message 2 of 3

Thanks for all the info, Rares. I managed to get it to work with DAQmx functions.



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