Start stop event structure queue

Hello,
I would like for the attached vi to start logging/displaying data when the Start button is pushed, not when the VI starts. So I did some research and was led to the Event Structure (this is my 1st time using an event structure). I have been trying all sorts of things over the last few hours so what I have now is probably somewhat convoluted, however, my latest error is that my dequeue is receiving an "invalid refnum".
Could someone guide me on what I am doing wrong?
Thanks.
Solved!
Go to Solution.
Attachments:
InitFile.vi ‏20 KB
CNAP Daq Event Structure.vi ‏109 KB

Hi Nouse,
I had some free time and was bored so took a look at your vi for you. You was on the right track, had started with a good architecture which is half the battle, just needed some fine tuning:
I took your code and added it to this. All that i have taken out is the Sub vi's that get your data, i replaced this with a random number just to see some data on the wavechart and also being logged in your file. A point to notice is that your 'CNAP INIT FILE' vi has no error cluster propogation. If you run this subvi and there isnt the 'C:CNAP\' Directory (As there wasnt on my computer at first) the 'OPEN File' vi errors and halts the program, as you have no error propogation or handling in this vi you cannot handle this error.
I changed the vi slightly and added a 'Start' 'Stop' and 'Exit'. This allows you to start acquiring/logging data, stop (without exiting the program), restart acquiring/logging or exiting the program. A point to note is that if you do 'Stop' and then 'Start' again, relatively quickly your 'CNAP INIT FILE' Vi will append a previously written file, which is fine, but it will also send out a new start time. So your readings in the same file will start from 0 time. You may want to catch this and not update the new start time if appending an old file.
I have attached the VI in both LV2009 and LV8.6 as you never stated your version.
Hope this helps,
Rgs,
Lucither
Message Edited by Lucither on 03-27-2010 03:32 AM
"Everything should be made as simple as possible but no simpler"
Attachments:
Data Logger VI 2009 and 86.zip ‏229 KB

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Attachments:
Uart.zip ‏140 KB

Your event structure will execute exactly once per loop of the main loop, thus the other three loops must stop before handlig the next event. You will also get a race condition between the top loop and the events when writing.
I'd put the top loop as the timeout case in the event and place the loop around the event for starters.
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Hi all
Attached is my Vi , I want to stop the event structure in loop 1 , from the loop 2 which is continously running in parallel and getting digital input from a DAQ device.
whats happening is first I am checking the status of teh digital input and then on that I am excuting the true structure. once I am in the True case , an event structure for user operations and a parallel while loop is used to monitor the digital input , what I want to do is as soon as the digital daq input is low again i should be back to my fasle case in the main loop but the loop 1 with event structure is not stopping.
help
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Attachments:
Untitled 1.vi ‏12 KB

Snamprogetti wrote:
You can't put an event structure into a case structure. It will run even if you are in the other case.
See http://forums.ni.com/t5/LabVIEW/An-event-structure-can-freeze-the-front-panel-even-if-not/m-p/106629...
What then, is a queued state machine? . The issue is the event structure still queues your events whether or not you are in your "idle" case. So if you don't promptly return to your idle case, events can back up in the event structure causing your program to act like it's lagging. Setting a busy cursor can help to solve this problem. I felt this should be clarified because a properly set up queued state machine is very powerful. This obviously isn't the solution for the parallel loops here but I thought I should add to your point..
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Unable to stop event structure manually

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Solved!
Go to Solution.
Attachments:
Motor-UNI_Directiona Dev 3.vi ‏53 KB
Control 1.ctl ‏6 KB
Control 2.ctl ‏6 KB

Uggh. I typed a response here to your note but NI website timeout kicked me out and I lost everything I typed.
What RavensFan mentioned is shown in attached image, you have to unclick that option on every case of your events structure so that it doesn't lock up the front-panel.
But more importantly as Lynn and other folks mentioned, you have a bigger problem with your design implementation. My previous example was to show how a state-machine based design can be made clean/small/efficient/etc. I have two 30" monitors on my Mac and your block diagram extends well into my second monitor!! :-) (I'm a bit of a neat-freak so I like making things look nice/wires laid out properly/into straight lines, no unnecessary wires crossing/etc - all that makes it easier for yourself and others to see the design.)
Sorry, back to the main point - you should definitely follow Lynn's advice on using Consumer/Producer (events) model - a simpler start would be to separate out your events structure into its own while loop that runs parallel to your existing loop. With that, at least you will execute events structure at a regular interval. Another strong advice is to simplify your design so that you don't use nested (one-inside-another) state-machine design. I have decades of LabVIEW experience yet I stay away from that kind of complication because it only causes more problems as you grow your design. Why not just add more cases to your existing state-machine design rather than adding a nested state-machine structure inside it?
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Attachments:
Untitled.png ‏75 KB

Stop events structure

Hi all!
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Attachments:
Doc12.doc ‏77 KB

Look, if you only attach a picture, we can only comment on what we see!
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You don't bring a picture of your motor to the mechanic and ask why the car does not start. Unless the picture show that the motor is missing or on fire, nonbody will be able to tell what's wrong.
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Solved!
Go to Solution.

Amitai Abramson wrote:
do you have a solution ?
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EXAMPLE2_MOD.vi ‏13 KB

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Attachments:
EventStructureHUH.vi ‏53 KB

Well ... the problem for me... was, for example, in the VI I posted....
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Message Edited by MJBrehm on 06-30-2006 02:21 PM

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lab1_3_try.vi ‏132 KB

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Attachments:
event.jpg ‏59 KB

This is a tunnel that has enabled the option "use default if unwired", this is the default option when working with the event structure.
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Attachments:
producer snippet.png ‏56 KB

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Stop execution of a loop in an event structure

I tried searching the forums to avoid posting a duplicate, but most I could not open most of the vi's as they were higher version.
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Solved!
Go to Solution.
Attachments:
FrontPanel.vi ‏34 KB

Right click on the event structure and choose "Edit Events" for the case that is giving you trouble.
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Can I get the event structure to NOT queue events?

I was wondering if it is possible to have the event structure not queue events that happen while the vi is executing code associated with another event. Basically, I have a toggle switch that, when "on", captures a live feed from a camera and displays it to the screen. This is done in a while loop that executes until the toggle switch is turned off. At this point, that event is done and the vi returns to the uppermost level of the event structure and resumes looking for events. The trouble is that the whole while the video capture was happening, the event structure was queueing events that were occuring during that time when the user was hitting other front panel buttons that had their own event associated with th
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> I was wondering if it is possible to have the event structure not
> queue events that happen while the vi is executing code associated
> with another event. Basically, I have a toggle switch that, when
> "on", captures a live feed from a camera and displays it to the
> screen.
I think there are lots of other articles about this on devzone.
To summarize them, the key is that the event structure intentionally
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asynchronously.
Usually there ends up being one loop with an event structure in it.
Another loop that executes a statemachine, possibly as simple as just
two states of acquiring and not. Use the events to pr
od the other loop
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How to stop While Loop in Event Structure with same button?

Hello,
I have a problem. I want to use one control to activate an event in a event structure, and the same control to terminate a while loop in that event.
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Message Edited by Heinen on 02-19-2009 06:16 AM
Message Edited by Heinen on 02-19-2009 06:20 AM
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Solved!
Go to Solution.

Hello,
I have a bit different problem.
I have a tab control, with several buttons on different pages.
In the current situation, we can talk about two pages, where one page ("Settings") in the Image, has a START and EXIT button, while second page ("Wait") has an EXIT button.
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When I click on Start in the Settings page, the front panel shows Wait page and attempts to connect to a datasocket server on the remote computer. If the user wants to stop this process, he can click on Exit on Wait page too. But, this doesn't give any immediate effect. On the even of Start button, the front panel is not locked, so the user can actually click the Exit button on the next page when it's visible. But it's of no immediate effect. Means, what the LabVIEW does is, finishes the execution of event in Start button's click, and while this executes, it doesn't consider the Exit button's refreshed value (shown in Red circle in the block diagram).
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Attachments:
terminate event_diagram.jpg ‏200 KB
terminate event_front_1.jpg ‏63 KB
terminate event_front_2.jpg ‏63 KB

Which is the best structure for start/stop data logging?

Hi everybody,
hope I can explain my problem good enough that anyone can help me:
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Attachments:
Logging voltage.vi ‏93 KB
screenshot.JPG ‏98 KB

@NaruF1 and GerdW
you are right, there is a mistake, both loop rates should be the same (10 ms) :-)
@NaruF1
yes you understood correctly that the file dialog should appear every time the user wants to start writing a new log-file. The voltage we measure is a analog signal, so there will be several interesting periods we want to save for a later analysis in Excel.
To your 2nd point: if it works with a array it will be fine. But it must be possible to log data for lets say 5 minutes, so the array won´t be too large? (5 min @ 10 ms loop rate will be 30000 rows..
attached is the VI, saved as LV2009..
Thanx a lot!
@GerdW
..you ask why I didn´t create a structure like you recommended with notifiers or queues? The simple answer would be that I am not familiar with all this.. just began to write my first Labview programm. I will have al look to the LV help with all that stuff... Thank you a lot
Attachments:
Logging voltage.vi ‏80 KB

Start stop event structure queue

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