You are correct. Each VI needs to finish before returning to the event structure. You need to have the event handler be totally separate from the event structure loop. Like most things in LabVIEW, there is more than one way to do this. Here are two.
- Create a VI which energizes a solenoid. This VI will energize the solenoid, wait a specified time, then deenergize the solenoid. Recommended inputs are the solenoid identifier and the wait time. Make it and all its subVIs reentrant, since you will be calling it from several places. For each solenoid, create a queue (use the energizing time as the data type) and a parallel loop to your main event loop. Put all the queue references in a cluster or array for easier handling in the event structure. Wire the cluster or array to the event structure. Wire the individual queue references to the parallel loops. In the event structure, when you get an event energizing a solenoid, put an element in that solenoid's queue. In the parallel loop, put a dequeue with an infinite timeout. When the dequeue occurs, run the VI which energizes your solenoid. When you exit, do a force destroy of all your queues. This will cause an error on the queues in the parallel loops, which is their signal to exit. This method does not scale very well because you need a parallel loop and queue for every solenoid, but it is simple and obvious for low numbers. It also has low latency between the button press and solenoid activation.
- Create a VI which energizes the solendoid, as before. In the event which energizes the solenoid, open a reference to the energizing VI using Open VI Reference. Since the VI is reentrant, you will get a new copy every time. Use invoke nodes (Control Value Set [Variant]) to set the execution time and solenoid specifier. Now use the Run VI method of an invoke node to run the VI. Set Wait Until Done to FALSE and Auto Dispose Reference to TRUE. This will cause the energizer VI to run as a separate process and return control immediately to your main program. This method scales very well, but has more latency due to the time needed to load the VI and set the front panel variables. If you build an application with this, make sure the front panel of the energizer VI is not removed.
Good luck. Let us know if you need more help.
