frequency problem in input-output control loop, LabviewRT

[Kocman]

Hello,

I want to write a cotrol loop in LabView real-time. My target is to acquire a data from 5 channel in frequncy about 100 kHz, integrate the data and send them to the output in frequency about 10 kHz (every 10th sample). I made twou time-loops. One for acquiring and integrating, second for sending them to output. This loops are connected throug the rt fifo. 

My problem is with a speed of acquisition. When I use "Hardware-timed single point" for acquiring, the result frequency is about 50 kHz. Continous sample and finite samples give me the desired frequency, but the output is not in in the same time as input (output waits until the input collects all data). Is there any problem with communication with the input and output channels in the same time?

My Hardware: 

Computer: NI PXIe-8108 in NI PXIe-1062Q

card: NI PXIe-6358

My vi is attached

[adamcseh]

Dear Kocman,

thanks for including your VI, it is useful to understand better your application.

However, the detailed requirements are still not entirely clear for me.

I think, starting with the right architecture and proper timing and synchronization schemes could save you a lot of effort while they ensure proper operation.

First, it should be defined what kind of timing your application requires. More specifically, if it needs to be hardware or software timed.

From your description it sounds like you would need hardware timed aquisition synchronized with generation, although your code tries to implement it using timed loops, which are inherently software timed.

You can find some useful additional information about the two methods and a nice white paper about synchronization techniques here:

https://www.ni.com/docs/en-US/bundle/ni-daqmx/page/synchronization.html

https://www.ni.com/en/support/documentation/supplemental/06/timing-and-synchronization-features-of-n...

Probably it helps to review them or even try to test some of the methods to get a better feeling about it.

I hope this helps you to get to the proper solution.

Best Regards,