Problem with nested event structures

[LabNEW90]

Hi there,

I am rather new to Labview and wanted to use a nested event structure in one of my programs.

However I seem to fail to do it right.

I created a minimal example of the construction I am using, you may find it in the attachment.

The basic idea in this program is the following.

1. I start the program and go into a while loop

2. Once I press and hold a front panel button a counter is increment every 100 ms.

3. When I release the buttun the incrementation stops.

However, this is not working. What am I doing wrong?

Thanks in advance!

[Norbert_B · Accepted solution]

Never stack event structures. Never ever.

That being said, your code contains quite some illogical parts, e.g. a wait time while using a 0-timeout event case.

Please use a single event structure. In case the increment should run, set the timeout case to e,.g. 100 (using shift register) and once it is pressed again set it back to -1. Initialize the shift register with -1.

Also avoid using references and property nodes to read/write values. These are bad practise (in most cases) and bury lot of runtime performance.

Use a second shift register to keep the numeric value and increase the value in the timeout case. Update the terminal after the event structure.

Norbert

EDIT: My first line is a rule of thumb. With increasing LV skill and appropriate design, stacking of event structures is possible, but you have to know the rules. If not, you will fail hard.

[BowenM]

You may find this to be useful reading:

http://zone.ni.com/reference/en-XX/help/371361J-01/lvhowto/caveatsrecmndtnsevnts/

[LabNEW90]

Thanks Norbert!

I changed the program like recommended and now it works smoothly!

However I kept the numeric ctrl reference. As I said this program here was only a minimal example of my problem and in the real program I have to perform a more complicated action on an instrument from which i got an automation refnum. So I wanted to test the whole thing with a reference.

I will upload my improved program here, for others who may stumble upon the same problem and want to see the solution.

Thanks again!

[LabNEW90]

Thanks Bowen, I will have a look at it in case I encounter further problems with event structures. 🙂