Hi all, I have an application using the producer/consumer architecture in which a queue passes messages from a main VI to a sub VI, in response to user events in the front panel. Inside the sub VI, the queue is dequeued and processed based on the dequeued message, and the result is displayed on the sub VI's front panel. The user events are captured in the main VI using an Event Structure. This works as expected. However, I would also like controls on the front panel of the sub-VI to be able to modify the queue. My approach is to have another event structure in the sub VI to do this. However, while the events in the main VI work fine, the sub-VI events never get processed. Attached is a simplified sandbox VI of what I'm trying to do. As you can see, events from the main VI are triggered as expected, but events in the sub VI are never triggered. I looked at this white paper: Detecting an Event in a SubVI from a Top Level VI but this is not exactly what I'm trying to do; rather, I'm just trying to detect an event generated within the sub-VI. I searched this board and found some related queries, but none of them seemed to address what I'm trying to do. ThanksMatt

Your major issue here is loop location. The While structure should be INSIDE of the subVI in order to make it a proper Queued Message Handler. In fact, you should have 2 loops inside of your subVI: 1) the QMH and 2) the event loop. You should use a User Event to commend the event loop in the subVI to stop. You should NOT be using the timeout of the Event Structure unless you absolutely have to. And since everything in that subVI is message based, you do not need any waits. They will be idle (using no CPU) when there are no elements to process from the queue or event queue.

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Event structure in both main vi and sub-VI with queues

Solved!

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Hi everyone,

Thanks everyone for the suggestions. Crossrulz's approach is, I think, the most straightforward (while loop for both QMH and Event Structure entirely within the sub-VI). I re-factored my sandbox VI to have this approach (which I have attached for future readers of this thread). This now works as I intended. After some preliminary investigation, I should be able to re-factor my real application to use this approach as well.

Thanks again!

Matt

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