Wait Function

[Ether]

Originally Posted by Mark McLeod

Some of the descriptions are probably over simplified.

Would this be an example?

a single Timed Loop set for 1ms and a higher priority will lockout your driver controls or make response very erratic, because the Teleop loop will never get time on the CPU.

I assume the above is true only if the code in the 1ms loop takes some significant percentage of 1ms to execute? In other words, the context switching overhead is nowhere near 1ms, is it?

[Greg McKaskle]

It is nowhere near 1ms. And the overhead of the loop is relatively small. Of course it very much depends on what you put in it, and whether you configure it to try to regain the schedule or slip it.

If you want to look at it under a microscope, you modify those sample loops to call into the RT Trace toolkit and that will let you see all the details of the scheduling. I've attached one of the example log screenshots. I would attach a typical 20ms teleop execution, but again, no cRIO at home.

Greg McKaskle

[WizenedEE]

None of your posts really say why a loop with a 10ms delay would run at 500hz consistently, just why it may be noisy. I think the original poster meant that it was pretty consistent with its 2ms time.

The probably may be that you didn't wire up a string to the "name" part of the vi, and you're calling it twice within the same vi. Not wiring up a name is fine for teleop, where there's only one loop, but you probably want to do it in periodic tasks, where there may be multiple loops you want to measure.

[Greg McKaskle]

Doh. That would explain a lot. I normally wire the string, but it was built so that when unwired, it will use the VI name. Are you calling the Elapsed time multiple times with the same string -- unwired from the same VI? Because honestly, I wasn't liking my explanation. I wouldn't expect more than about 2ms of noise jitter.

Greg McKaskle

[cabbagekid2]

No, we only call the elapsed time vi once in periodic task and once in teleop. Both times we left them un-named. But it should be okay since we only dropped it in one of the while loops in periodic task and not multiple loops?

[Mark McLeod]

Something is incorrect.
Care to zip and post the project as-is?

I ran a test on the default framework to be sure and I get 10-11ms