Is it possible to use key down event to stop a while loop?

[KTG87]

Hi,

As the subject says, it is possible to use a key down event (wired to the stop terminal) to stop a while loop from running? More specifically, I need to use the "S" and "L" buttons to do this.

All feedback is much appreciated!

Thanks.

[RavensFan]

Message Edited by Ravens Fan on 03-22-2009 10:14 PM

[KTG87]

Spot on! Excellent, thanks for that.

[KTG87]

I'm having trouble using a key down event to stop a while loop.

I am using the structure in the attached picture.

I want the VI to display a random picture (first frame of the flat sequence) and then wait a certain amount of time (second frame of the flat sequence). I want this process to repeat until the spacebar is pressed (the event structure with a key down event) which terminates the while loop.

For some reason, instead of doing this the structure displays a random picture, waits for a keystroke and once it is pressed it then waits and the VI stops after. If I completely remove the event structure, and just have the while loop on Continue If True, the picture generation and wait work fine so I figure the problem has something to do with the event structure.

Any help is always appreciated!

[altenbach]

Your event structure blocks the loop from spinning. The loop cannot repeat until everything in it has completed and your event structure only completes if a key is pressed. Think dataflow!

Try execution highlighting for debugging.

Quick solution: make the event structure transparent by adding a timeout case and wiring a reasonable value to the timeout terminal.

Not much more can be said. Your VI image is incomprehensible because things are hidden and/or unlabeled. Also some things make very little sense. Why don't you attach the actual VI instead of a picture? It would be much easier for us to debug!

[KTG87]

Attached is the VI (it is run as a subVI in another program).

Sorry about the lack of information.

[GerdW]

Hi KTG,

here's a vi with cleanup and additions as mentioned before...

Have a live outside - it's Easter

[KTG87]

Thanks GerdW!

I've only been using Labview ~5 months with no background in any sort of computer programming so any help I get is more than appreciated!