Slow loop inside fast loop

[Saguenay]

This is my first week working with LabView so the answer might be very simple.

Here's my question:

How do I include a slow loop (event B)  inside a fast loop (Event A)?

What I would like is for Event B to execute every 1000 milliseconds and Event A every 100 milliseconds.

Where Event A is a position control loop and Event B is a simple write to file of some measurement.

Any recommendation on how i should accomplish this?

[Pnt]

Put the slow loop outside the fast loop.

They will run in parallel.

[Baji]

Generally I handle this kind of requirement with the producer-consumer architecture.

The Producer/Consumer pattern’s parallel loops are broken down into two categories; those that produce data, and those that consume the data produced. Data queues (which are covered more in-depth in the Queued Message Handler section) are used to communicate data between loops in the Producer/Consumer design pattern. These queues offer the advantage of data buffering between producer and consumer loops.

Source Link: http://zone.ni.com/devzone/cda/tut/p/id/3023

[jcarmody · Accepted solution]

You can use an Elapsed Time Express VI inside the fast loop to see if it's time to execute the slow loop.  I took the liberty of not using a loop for your "event B" because it sounded like you just want to pace it with event A.  Put event B in the True case of the Case Structure. The producer/consumer design pattern is the way to go if you're developing a complex application. This'll do if your problem is relatively simple.

 

[Saguenay]

Thanks for the solution

I also found that passing data between parallel loops with local variable could do the trick

[Pnt]

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Saguenay wrote:

I also found that passing data between parallel loops with local variable could do the trick

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Local variables can lead to race contitions, when they are be used for that reason.

Search for "race contitions" on this forum for more info.

Better use "function globals"

Do a little search