topic Re: Continuous event queue ? in LabVIEW

Continuous event queue ?

supermango — Fri, 08 Sep 2006 13:01:17 GMT

Hi,

I'm using LV6.1 and I got a little problem with events. How do I make a continuous event queue for activex component, that means LV will respond every time when mentioned event fires instead of it responds just once. Does anyone have an example ?

Thanks in advance!

Re: Continuous event queue ?

Will.D — Fri, 08 Sep 2006 13:32:26 GMT

I have never used events in 6.1 but assuming they function the same as they do in later versions, the events are queued continuously.

You event structure should be in a loop, and the event triggers will be queued as they arrive.

If you want to prove it out, create an event structure in a loop that fires when you click a button on the front panel. Have a counter count each time the event is fired, and have a few second delay in the loop. If you keep clicking that button faster than the delay in the loop, you won't see anything happen immediately, but the event counter you created will eventually match the number of times you pressed the button.

Re: Continuous event queue ?

TCPlomp — Fri, 08 Sep 2006 14:29:39 GMT

Hello Supermango,

do you unregister for the activeX event inside the VI that reacts on the event? in that case you will loose the funictionality you wnat. Could you show some code?

Ton

Re: Continuous event queue ?

km76107 — Wed, 13 Sep 2006 19:11:27 GMT

I apologize that I do not have an answer to your question. But it seems like I have a similar issue. I have 2 while loops and would like to have one event run continuously when another event is fired. I'd appreciate any advise. (See attached vi)

Thanks

Re: Continuous event queue ?

MJBrehm — Wed, 13 Sep 2006 19:58:19 GMT

KM,

I dont think you need an event structure at all.... Here, check this out. Is this along the lines of what you were looking for?

Re: Continuous event queue ?

altenbach — Wed, 13 Sep 2006 20:44:27 GMT

It seems silly to even use two loops:

If you require two loops and want to use an event structure (maybe the rest of the code requires it), you can manipulate the event timeout, e.g. as follows.

Message Edited by altenbach on 09-13-2006 01:45 PM

Re: Continuous event queue ?

km76107 — Thu, 14 Sep 2006 14:13:34 GMT

Hi altenbach and brehm:

THanks for the prompt response and the VIs. You are right... it really seems silly to use 2 while loops. Maybe there is a better way of doing what I am currently doing. I am trying to modify the "New Event Handler" example that ships with LV. I am creating an Intrusion Detection System. My program has three basic functions: Acquire data continously via TCP/IP, analyze data (which includes multiple operations on demand such as different types of data analysis, image analyses and graphing) and display/archive data (which includes multiple operations on demand such as different display formats). I am new to Event Structures and I thought that using events might be the best option to optimize CPU speed and memory. Any suggestions/advise on improvements? Thanks again.

Re: Continuous event queue ?

NathanT — Wed, 11 Jun 2025 15:22:54 GMT

km,
Take a look here.

-Nathan

Re: Continuous event queue ?

km76107 — Mon, 23 Oct 2006 14:36:44 GMT

Altenbach,

I am using your example as my reference. Instead of sending the value of A to B in the same VI, i am calling a subVI and continuously sending the value of A to that subVi when the OK button is pressed (see attached code). I am not sure why the code isn't working. Also, I notice that the CPU usage increases drastically. Any suggestions? Thanks in advance.

Regards

Re: Continuous event queue ?

NathanT — Tue, 24 Oct 2006 23:57:11 GMT

km,
Have you tried debugging the code using highlight execution so you can see what is going wrong?

Thanks,

NathanT

Re: Continuous event queue ?

km76107 — Wed, 25 Oct 2006 02:01:46 GMT

yes i have and i think i know what i am doing wrong.. i was hoping to mock up my messy (and actual) code with a simple example given by altenbach.. here is my scenario:

I am reading from a server continuously using TCP Vis every 5 seconds..this is my first loop. I am using queues to pass the data to the second loop, which processes the data..i have a 3rd loop that is event driven by a boolean's value change which consists of a subvi that allows to configure the settings of the server by writing to the server via TCP write. The configure subVI has multiple events, such as changing transmission time, changing settings etc. which are all event driven as well.... I'd like to be able to pass the data from my first loop into the subvi such that the subvi contains the streaming data in the first loop.

Problem: I am unable to continuously send the data to the subvi because my configure subvi is supposed to open its FP when called. I have posted this code in another similar discussion forum and someone suggested to use Globals within the event structure of my Configure VI... this works fine only when the event is triggered... however, i'd like the data to be continuously updated in the subvi and use the current data for my events.

I hope what I explained makes sense... I'd appreciate if you can suggest a method to implement my code.
Thanks
KM

Re: Continuous event queue ?

NathanT — Wed, 25 Oct 2006 19:18:13 GMT

km,
Is the user changing the boolean control that triggers the event? I have modified your code heavily and also added it to a project in order to use a shared variable. Take a look and see if that is closer to what you are looking for.

Thanks,

NathanT

Re: Continuous event queue ?

km76107 — Wed, 25 Oct 2006 19:33:14 GMT

hi nathan,

Could you post the code in LV 7.0 or 7.1.1? I don't have LV 8.0

thanks

Re: Continuous event queue ?

NathanT — Thu, 26 Oct 2006 18:35:46 GMT

km,

Here you go. Unfortunately I had to take the shared variables out since they are not supported by 7.1. Keep in mind this is just an example to demonstrate the use of VI server and property nodes. Use it as a rough starting point if you would like.

NathanT

Re: Continuous event queue ?

km76107 — Tue, 31 Oct 2006 17:48:12 GMT

Sorry for the delayed response Nathan. Thank you for posting the code.

Re: Continuous event queue ?

NathanT — Wed, 01 Nov 2006 20:04:31 GMT

I am glad to help you out km. Good luck with the rest of your application.

NathanT