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CRIO 9189 ethernet slower than CRIO9174 USB

Hi, I am writing a code to control some actuators which need a 24V signal. Very simple ON/OFF. My code is structured with one while loop that scans a boolean matrix which contains the state of each actuator every dt of the loop.

 

I have initially developed this code with a CRIO 9174 USB, but since I needed more than 4 slots I am now using a CRIO 9189 which works through ethernet. Since I have changed the CRIO I have noticed that the speed of the while loop has decreased. Is that normal or is there any settings on the ethernet that I should check?

To give you an idea, if I operate with 8 channels DO it goes from 9ms to 13ms, 12 channels 14ms vs 23ms, 20 channels 43ms vs 65ms.

 

I have attached screenshot of the code and the boolean. Is there any quick fix to make the loop faster? Ideally I would like the square wave to be at 20Hz which would need at least 25ms. At max I have a total of 64 channels which makes things worse. I have planned to move to a PXI in the future, but perhaps there is something I can do now.

 

Many thanks for the suggestions!

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The pic doesn't show enough to answer this question:

 

Do you explicitly call DAQmx Start *before* entering the loop?  If not, try that as your first step.

 

A better overall approach for faster and more consistent timing is to include a call to DAQmx Timing to set up a hardware sample clock and a buffer.  Have a look at some shipping examples for hardware-timed output and experiment a bit. 

 

If you know your output sequence ahead of time, a Finite Sampling task can be just as simple to program as your software-timed approach.  Continuous Sampling tasks *can* require a little more programming finesse, but they offer a lot of advantages when you need higher sample rates, data bandwidth, and unknown durations.

 

 

-Kevin P

ALERT! LabVIEW's subscription-only policy came to an end (finally!). Unfortunately, pricing favors the captured and committed over new adopters -- so tread carefully.
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Many thanks for you prompt reply. Since there is a deadline coming up, I had to accept to operate at 5 Hz for the time being, but I will go back to this in two weeks time and try your suggestions. I will update here regarding the progress. 

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