Question about parallel daqmx tasks on cDAQ-9188

[Crispie]

Hi,

I have a cDAQ-9188 chassis, housing four NI9203 modules.

I currently have two tasks which I wish to run under NI-DAQmx, one is acquiring 14 channels of analogue inputs (at 750 S/s) and the other is monitoring an encoder connected to the PFI inputs on the chassis.

I have configured the AI task to trigger an event every 75 samples, and I have configured this to be processed in the main execution thread.

I am using the execution profiler, and if I have the AI task running, the encoder task takes around 30ms each time to obtain a reading - it the AI task isn't running, this drops down to around 2ms which is much more reasonable.

Surely it must be possible to run these tasks in parallel without such a detrimental affect to the time taken to obtain an encoder reading?

What should I be doing to allow these tasks to run comfortably side-by-side?

Thanks for any help,

Chris

[niNickC]

Hello Chris,

I think it should well be possible but obviously there are a lot of variables here.

Could you possibly attach the code you are seeing this behaviour? I am happy to take a look and see if there is anything I can spot.

Also, this application is obviously dependent on the Ethernet connection, what is the context of this system in the network?

Best Regards,

[Crispie]

Hi Nick,

Sorry for not replying sooner, I've not been in at work.

I'm attaching some files which are a much stripped down version of my project.

In this cut-down version, the read encoder call takes approx. 10ms when the AI task is running and 1-2ms when it isn't, so it doesn't exactly duplicate my issue, but is representative.  The timings I'm quoting are obtained from the execution profiler.

Thanks in advance,

Chris