Hello All. I have a calling sub-vi with a "Start Test" button on the front panel. I passed a control reference for that Start button into a sub-vi that runs in a while loop. The while loop is monitoring that Start button and other things. Problem: Once the sub-vi runs, it no longer takes updates from that Start button. My program never leaves that while loop in response to my Start button. Is there some way I can make the sub-vi take an updated value from the calling vi? Attached is the sub-vi (top level, LabVIEW 2011). Please note that I have already tried putting the Start Test terminal inside the loop, but that did not help. I put comments in the block diagram and the front panel to help identify the problem code. I am going to get around this problem by running this whole vi through a loop in the calling vi, where I can easily respond to button changes. This is mainly an academic or curiosity problem now. Thank you, Richard V

You should look at the Syncronization pallette and become familiar with the Queue and Notifier constructs. These are very useful for passing data between VI's.

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LabVIEW

Calling vi front panel object update in a running sub-vi loop?

Solved!

@aputman wrote:

No biggie man. I agreed with your comment that it was a little overcomplicated but it would work just fine. I am by no means a LabVIEW expert. Sometimes I get in a rush to type out my answer without thinking things thru fully.

So is the reason for your concern becaus there is no coupling between the control update and the local variable read that enforces data flow?

Yes, that is one of my concerns. I think execution may get stuck in the center while loop depending on the mechanical action of the button in the main VI. If it latches, I could see that the subVI never gets the updated value. But if it is set to switch, I don't see why the OPs code doesn't work.

Thanks! Sometimes reading dataflow is so complicated that I need to see if I am seeing the same thing. 🙂

Bill

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