How to exit from the DO-while loop in the event structure

Hi all
I am just a beginner for Labview
I want to build a loop in the event structure, but when I enter in the loop, it seems the system is dead, and I can't exit the loop.
here I attached a simple sample.
In the sample. when I press the start_calculation button , the calculation start, but the system is dead, and I can't exit calculation loop.
actually, i just want switch the different operation by changing the event action.
anybody has a good idea about it??
thanks so lot
Attachments:
event_problem.vi ‏17 KB

Your problem is that you are trapped inside an event case. It is not a good idea to run extended code inside event cases, else the event structure cannot service other events.
Why don't you use the outer loop for everything? Now things don't step on each others toes. What good is an event structure if it cannot react at all times???
Message Edited by altenbach on 07-25-2008 12:26 AM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
event_problemMOD.vi ‏17 KB

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Event controll: How to stop a running while loop inside a event structure

Hello,
I have some problems with controlling a while loop inside a event structure (see attached VI).
I habe 3 buttons ("Start Measurement, Stop Measurement, Quit Program"). When a measurement is running, it should be possible to stop the measurement by clicking on "Stop Measurement", but this does not work.
Has anyone an idea?
Thanks a lot and best regards,
Michael
Message Edited by MichaGue_01 on 04-23-2010 04:37 AM
Solved!
Go to Solution.
Attachments:
Event_Controll.vi ‏27 KB

Hello,
Try not to use while loops inside a Event structure.
My approach is using two While loops (one will have only the Event structure).
I had to use to Flag buttons that make it a bit more complicated but i am sure somebody will come up with a better idea, or you might want to have a think about it yourself.
Have a look on the modified version on the attachment.
Once you are happy how it works then you can Hide the 2 flag buttons from the Front Pannel by going to Block diagram right-click the indicators and choose option "Hide Indicators/Controls"
I did it in LV 8.6 so i hope you can open it on your PC if not i can downgrade it.
If you have any problem let us know.
Regards
Dimitrios
Test Systems Computing Engineer
Cummins Turbo-Technologies
Attachments:
Event_Controll[1]_modified.vi ‏18 KB

How to pass a value from inside a while loop outside the loop

Hello to everybody, I have been searching through the forum but I have not found a certain answer for my problem. I would try to explain my problem as breefly as posible:
I have to send by a BNC2120 two signals and acquire an other one thats comes from a preassure sensor. That part is done by introducing simulating and acquiring DAQmx inside while loops.It is sycronized by my self, proving such diferent values (is not the optimum, but is only the first prototype) and works as I expected. Well, then I want to sample some of the values of these signals, that is done with relays and local variables to get the value in the instant I want to sample. Here begin my problems: I want to extract the sample values out of the while loops without restarting them, I mean: I do not want to stop the while loops because the acquisition and the generation of the signal must be continuous, but I do not know if it is posible to put the while loops in "standby" until I operate with the values I have sampled and then the signal generator and the acquiere continues from when it has stoped before. Particulary I want to obtain the value of the top while loop (inside a case) when the counter arrives at 15.
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Attachments:
maq_estados_event_case.vi ‏239 KB

It definately sounds like what you really want is a Producer/Consumer. It is an architecture that uses Queues to pass data from a data generation loop (producter, your DAQ loop) and a data processor (consumer).
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While loop inside a event structure

Dear
I have no much concepts on event structure.
Let's assume there is a dialog box with Okay and Cancel button.
I put the event structure for Okay and Cancel button.
In Okay event, there is a while loop for detecting some data continuously.
In this case, I want to use Cancel button to stop the while loop during the detection.
How can I do to receive signal from the Cancel button?
Thank you in advance.

I'm not sure that the event structure should be used to handle that situation : while the OK event is executing, either the Front panel is locked and new occuring event will be stored until the OK event is completed (so the Cancel button action will not be detected !) or the Front panel is unlocked (see below *) and the Cancel button action will stop the loop, but the Cancel button event case will not be executed, since the event has already been processed in the OK case !
You should probably use a single button to run/stop the loop, as shown in the attachment
* While editing the event case, unmark the "Lock front panel for this event complete" at the bottom. But of course, the code in the cancel case will not run, since the event occuredMessage Edité par chilly charly le 03-31-2007 05:27 PM
Chilly Charly (aka CC)
E-List Master - Kudos glutton - Press the yellow button on the left...
Attachments:
Event button.vi ‏11 KB

How to Exit from Session by executing program

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I have a VI that contains front panel clusters and two while loops. The main cluster contains items such as a doubles "distance" and "stepsize" and boolean "step" (a whole buch of this type stuff). The first loop contains an event structure to detect front panel changes and the second contains code and sub VIs to perform operations based on detected events.
The operator can enter data into either double or click the boolean. If distance is changed the second loop does what is required to process the change. The same happens with stepsize. If step is clicked the ±stepsize value is added to distance and the result is processed. In each case the front panel should track the result of the input and subsequent processing.
Because the clusters are outside the while loop, they are not updated unless I click 'highlight execution' which seems to allow updating each time the execution highlight is updated. There are other issues if I move the clusters into one of the loops.
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Thank you for the response. I followed the link and tried reading everything you posted on AEs but I'm afraid that I didn't understand it all. It seems that each AE example had a single input and a single output (e.g. a double). Is this the case?
What I have is a couple of front panel clusters containing (approximately) 18 control doubles, 8 indicator doubles, 5 boolean radio button constructs and 26 boolean control discretes. I clusterized it to make it readable. In addition I'll eventually have a cluster of task references for hardware handles.
All I want to do is update the front panel values like I would do in a C, VB or any other language. I've tried referencing the cluster and using the reference from inside the loops. I've tied using local variables. Neither works. I'm experimenting with globals but it seems that I have to construct the front panel in the gloabal and then I wouldn't know how to repoduce that on the front panel of the main VI. Sometimes it seems that more time is spent getting around Labview constructs than benefitting from them.
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Attachments:
Front Panel Reference.vi ‏33 KB

I am using the "Menu Selection With Events.vi" example alongside other while loops, When I select exit from the new menu it stops the other while loops but not the menu/event while loop

The event driven menu example works fine and I've integrated it into my application. I have built in simple local vars to link menu selections to existing GUI buttons. The problem is that I cannot get the File-Exit menu option to switch off/terminate the application. The [1] "Stop": Value Change panel of the event structure simply switches off the other while loops but leaves the event while loop running. Add a while loop to the axample using a local var from the event while loop to terminate 2nd while loop to get the effect.
Help appreciated, Chris

Attached you will find a modified version of your VI.
I documented what I did on the block diagram.You were right on you just needed to add a variable with a true wired to it.
Have fun with it.
Joe
Joe.
"NOTHING IS EVER EASY"
Attachments:
Menu_Selection_with_Events_%26_while_loop[1].vi ‏76 KB

How to exit from the loop

loop at itab.
if <CONDITION>
<EXIT LOOP>
endif
endloop.
this ths condition , pz tel how to exit from loop

Hi
Loop
statements
EXIT
Endloop.
Will comes out of the loop.
Regards,
Sreeram Kumar.Madisetty

How to code a parallel 'for loop' and 'while loop' where the while loop cannot terminate until the for loop has finished?? (queues also present)

I've attached a sample VI that I just cannot figure out how to get working the way that I want. I've labeled the some sections with black-on-yellow text boxes for clarity during the description that follows in the next few sentences. Here's what I want:
1) overall -- i'm intend for this to be a subVI that will do data acquisition and write the data to a file. I want it to use a producer/consumer approach. The producer construct is the 'parallel for loop' that runs an exact number of times depending on user input (which will come from the mainVI that is not included). For now I've wired a 1-D array w/ 2 elements as a test case. During the producer loop, the data is acquired and put into a queue to be delt with in the consumer loop (for now, i just add a random number to the queue).
2) the consumer construct is the 'parallel while loop'. It will dequeue elements and write them to a file. I want this to keep running continuously and parallel until two conditions are met.
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Here's the problems.
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2) I can easily get the outer for and while loops to run sequentially, but I want them to run in parallel. My reasoning for this is that that I anticipate the two tasks taking very different amounts of time. .. basically, I want the while loop to just keep polling the queue to get everything out of it (or I suppose I could somehow use notifiers - suggestions welcome)... the thing is, this loop will probably run faster than the for loop, so just checking to see that the queue is empty will not work... I need to meet the additional condition that nothing else will be placed in the queue - and this condition is met when the for loop is complete. basically, I just can't figure out how to do this.
3) for now, I've placed a simple stop button in the 'parallel while loop', but I must be missing something fundamental here, because the stop button is totally unresponsive. i.e. - when I press it, it stays depressed, and nothing happens.
suggestions are totally welcome!
thanks,
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Attachments:
daq01v1.vi ‏59 KB

I'd actually like to add a little more, since I thought about it a bit and I'm still not quite certain I understand the sequence of events...
altenbach wrote:
zskillz wrote:
So i read a bit more about the 'dequeue element' function, and as I understand it, since there is no timeout wired to the dequeue element function, it will wait forever, thus the race condition I suggested above can never happen!
Yes, you got it!
As I've thought about it a bit more, there's a few things that surprise me... first, the reason the 'dequeue element while loop' errors is not because there's nothing in the queue, it's becaues the queue has been released and it's trying to access that released queue... However the problem I have is this --- Even though there's no timeout wired to the dequeue element, I still would think that the while loop that contains it would continue to run at whatever pace it wanted -- and as i said before.. most of the time, it would find that there is nothing to dequeue, but once in a while, something is there. however, it seems that this loop only runs when something has been enqueued. the reason I say this is illustrated in the next code sample MODv2 that's attached below. I've added a stop button to the "queue size while loop" so the program runs until that is pressed. I've also added a simple conditional in the "dequeue while loop" that generates a random number if it a button is pressed... but this button is totally non-responsive... which means to me that the "dequeue while loop" isn't actually continuously running, but only when an element is added to the queue. this still seems almost like the 'dequeue while loop" waits for a notifier from the queue telling it to run. can you explain this to me? because it is different from what I expect to be happening.
rasputin wrote:
I tried to open your VIs but it doesn't work. LV
is launched, the dialog box (new, open, configure...) opens and then...
nothing. Not even an error message. I guess it isn't a problem of LV
version or a dialog box would appear saying this. Could you, please,
send a image of the code?
Thanks,
Hi Rasputin, I'm using LV8. I assume that was your problem, but who knows. I've attached a pic of of altenbach's solution since it's what I needed.
thanks
-Z
Message Edited by zskillz on 10-20-2006 11:49 AM
Attachments:
daq01v1MODv2.vi ‏63 KB
daq01v1MODpic.JPG ‏116 KB

How to exit from a loop on 2 different conditions

Hello Experts
I’m trying to write a procedure in which I’m taking PROVINCE as an input parameter. All the provinces are stores in a table. I’m using a cursor and rowtype variable to check the province. After I finds province I displays province and its code. Everything works fine expect when I don’t find the province. I’m not sure how to exit from loop if I don’t find the province. I already uses exit when condition. I was expecting else condition should work and should exit from the loop but it doesn’t. Can please somebody show me how to exit if I don’t find province in the table through cursor.
Here is my code
set serveroutput on
variable G_TAX varchar2(10)
CREATE OR REPLACE PROCEDURE p_create(i_state VARCHAR2)is
CURSOR cur_bb_tax is
select * from bb_tax;
bb_tax_details bb_tax%rowtype;
begin
if not cur_bb_tax%isopen then
open cur_bb_tax;
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loop
fetch cur_bb_tax into bb_tax_details;
if (bb_tax_details.state = i_state) then
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exception
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Why don't you use dbms_output.Put_line and print output to find why logic is not able to execute? Maybe upper case/lower case/whitespace. *Also put your code between \ to preserve formatting*.
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Hi,
I am having some trouble with my ipod 7th gen.
First my lightning cable wont be recognize. show the error Accesory incompatible.
I try to solve the problem cleaning the golden pins in the cable and in the ipod. Don't work
I enter in diagnostic mode in my ipod and I get stucked in the button counter test..
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Your problem is that you are trapped inside an event case. It is not a good idea to run extended code inside event cases, else the event structure cannot service other events.
Why don't you use the outer loop for everything? Now things don't step on each others toes. What good is an event structure if it cannot react at all times???
Message Edited by altenbach on 07-25-2008 12:26 AM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
event_problemMOD.vi ‏17 KB

How to exit from loop after 3 time

hi
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loop at itab.
<exit after 3 time>
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thanks

Hi,
You can check the value of SY_TABIX inside loop,
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if sy-tabix = 3.
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My daq 6008 wil not drop the 5V after the VI is stopped, i have a digital signal going from the error out on the daq in the while loop to the error in on the daq outside the while loop and a boolean going to the data of the daq outside

my daq 6008 wil not drop the 5V on a digital output after the VI is stopped, i have a digital signal going from the error out on the daq in the while loop to the error in on the daq outside the while loop and a boolean going to the data of the daq outside, but i can t seemto get it to work

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Attachments:
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How to exit from the DO-while loop in the event structure

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