What is the best way to pass a controllin​g signal out of a sub vi or more than one layer of for loop, while the sub vi or for loops are still running?

Question

I have a vi that runs through two for loops and a while loop, then after a certain number of iterations on the inner while loop it is supposed to pass a trigger to a case stucture to start measurement. I have tried using a local variable attached to a boolean control which in turn is attached to the true case of the case structure involving the measurement sub vi. What is happening is that the boolean control will light on the front panel at the correct # of iterations in the while loop, as if true, but the measurement is not taken, and the boolean control never goes back to false. It remains lit. Am I u
sing the local variable incorrectly? If so, where am I going wrong.
Attachments:
GL_Flicker.vi ‏118 KB
Take_Measurements.vi ‏147 KB

Answer 1

Hello planar,
There are multiple ways to pass control information between loops and VIs and each one has its place. For simple VIs like your example, a local variable will be fine.
The main reason the subVI is not running is that the case structure is not continuously polling the Boolean control. This is because the case structure is not inside a loop and as such will only read the Boolean value once and execute once. Encasing the case structure and control inside the while loop should solve the issue of the subVI not running.
You may find the following links of help in creating more robust and advanced VI architectures.
Application Design Patter
ns: Master/Slave
LabVIEW Application Design Patterns
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