Stopping Timed Loop inside a Reentrant VI

I just converted a project over from 8.5 to 2009 and I found that some of the funtionality that was working in 8.5 no longer works in 2009 (probably for good reason...).
Anyway, I found that if I tried to use the stop timed loop vi to stop any timed loops in reentrant vi's that I get a -804 error. The stop timed loop sub vi was in the same reentrant vi in the application, but I found it also did not work if it was outside the reentrant vi.
It does get a little hairy when thinking which loop you are trying to stop because of the reentrancy, but if the names passed into the instances are different for the loops then it shouldn't be a problem right?
See attached for a very simple example of this occuring.
Note: Just running in windows...not in RT
Solved!
Go to Solution.
Attachments:
Stop Time Loop.LLB ‏41 KB

I resorted to using an alternative way to stop the loops as well. Does anyone at NI know if this is a feature or a bug or if there is anyway to use the stop timed loop function with a timed loop in a reentrant vi?
Thanks.
Whoops... Just read your post. Thanks for the update.
Message Edited by klessm1 on 01-06-2010 10:55 AM

Similar Messages

Error -50103 occured with timed loop inside a while loop

Hello everyone,
i wrote an application to sample analog voltage from DAQ6024E card (see the attachments).
I have a big while loop in the VI because a I want to add some other functions later.
In the "WHILE_Cont Acq&Graph Voltage-Int Clk.vi" I use a while loop inside the big while loop to read the samples. It's working properly.
but when I use a timed loop inside the big while loop (see "TIMED_LOOP_Cont Acq&Graph Voltage-Int Clk.vi"), I get an error -50103 from the timed loop. It seems that the first cycle is ok, but after the first cycle the error occurs.
I don't know what happens with the timed loop, anyone can help me? what does the error -50103 mean? thanks a lot!
PS: I am using LabVIEW 8.0
Message Edited by molo511 on 10-22-2006 05:21 AM
Message Edited by molo511 on 10-22-2006 05:23 AM
Attachments:
TIMED_LOOP_Cont Acq&Graph Voltage-Int Clk.vi ‏143 KB
WHILE_Cont Acq&Graph Voltage-Int Clk.vi ‏75 KB

hi molo511,
I tested your program but only with simulated devices. I had to delete the wire to the timing, so that the timed while loop runs with 1kHz. Did you already try this? Because this works on my PC.
I also found a link in our database that might be interesting for you.
http://digital.ni.com/public.nsf/websearch/04BEDD9E9E91ED3486256D180048116D?OpenDocument
Greets
Philipp N.
NI Application Engineer

Timed loop inside a flat sequence not terminating

Inside a while loop there is an event structure. Inside that there is a flat sequence. On one of the frames there is a timed loop that quits after so many iterations. The timed loop finishes but the flat sequence doesn't execute the next sequence. What am I not doing right?

First, you have too many local variables. This could be leading to race conditions.
I think you have a couple problems in the use of event structures. It is a bad idea to put any long running code inside an event case. It will prevent the Event Structure from handling any other events in the mean time. You have several timed loops running that in that one sequence frame.
But the bigger problem is the next sequence frame. You have a while loop that only ends once all the queues are empty. Can you guarantee that all the queues get emptied?
You have laid out the code very neatly, but you have used a lot of odd things in there. (Number to boolean array, to cluster, to unbundle the cluster to individual indicators.) Why not just go from Boolean array to and index array function. No need for the intermediate cluster conversion. Why not set up the indicators as an indicator array and just write to them directly.
The code is so much intertwined between when queues are created, filled, emptied, destroyed, events happen... And this is all multiplied by at least 4 times for each camera. And there are 4 major event structures going on. This is a very ambitious project for an inexperience LabVIEW user. You need to step back, get one thing working right, and design so that you can scale the architecture upward. Many of the structures you have essentially duplicated and belong in subVI's.

Restarting counter in Timed Loop

I have a timed loop inside a state machine, used to start/stop a data acquisition sequence.
It works fine, but I'm monitoring the "i" count and Actual End [i-1] values and after the start/stop/start sequence
these values continue to grow and don't get reset to zero. I would expect a While Loop to reset the "i"
variable every time is is called, but I don't see any option for resetting the time looped.
I can get around it, but I would expect a reset method for this loop, so I'm just wondering if I'm missing something.
Maybe I need to use "Create Timing Source" instead of the setting it iin the dialog box?
Labview 2010f1 on Windows Vista SP2 PC

This might help. Here is a part of the png file you posted. I put in "Structure Name>" to point to the Structure Name input. Notice that the name "bob" is listed as the Structure Name. You must be on Win7 which uses different fonts than XP - that's probably why the name is only half visible.
Note that the Clock name is connected to the (timing) Source Name input.
I'm attaching an updated version of the file with the Timing Loop name wired directly.
Thanks for posting your timed loop interations3 program in 2009. When I run this code, the Iteration Count DOES reset when the Timed Loop is restarted.
steve
Help the forum when you get help. Click the "Solution?" icon on the reply that answers your
question. Give "Kudos" to replies that help.
Attachments:
New timed loop interations.vi ‏42 KB

How to stop a while loop which contains a timed loop

Hi,
I'm a new hand to labview, and I'm using labviw 7.1, NOT 8.x. I'm trying to do a measurement, in which the flow would look like the attached file (I have stipped all hardware related components to make it easy to read). My questions are:
1. In Loop 3, when the comparison (x>20.85) is true, Loop1, Loop2 and Loop3 are stopped, why it won't quit the while loop (I have wired it to while loop stop)?
2. When it is running, I click on stop button, why it won't stop?
Thanks!
Attachments:
SyncTimedLoop32.vi ‏228 KB

hwm wrote:
2. When it is running, I click on stop button, why it won't stop?
The stop button is read outside of the inner while loops. So the inner while loops will continue to run until their stop conditions are met.
hwm wrote:
1. In Loop 3, when the comparison (x>20.85) is true, Loop1, Loop2 and Loop3 are stopped, why it won't quit the while loop (I have wired it to while loop stop)?
It seemed to me like it would, but sometimes it seemed like I had to set change the numeric value one more time before it would. You have a very odd structure there by placing the event structre inside the while loop with the other loops. I think you may be running into issues where events are getting queued up in the event structure, or race conditions between when the event structure might execute relative to the other loops. It is all very odd and difficult to predict all the ways these structures might interact and relative timing. Usually event structures would belong in their own parallel while loop. I think you need to rethink exactly what you are trying to do here. It probably isn't event necessary to use the stop timed structure functions. A local variable or a notified to pass the "Stop status" from loop 3 to the other loops (or the separate event structure loop to the other 3) would probably be better.

Run once inside timed loop

I have a timed loop that monitors equipment. Whenever there is a fault I have it send a notification email. My problem is how to stop it from sending email every single time the time loop is executed. I tried placing the send email inside a for loop but quickly realized that the entire loop itself is reiterted. Any help is much appreiciated.
Solved!
Go to Solution.

Hi icemaker
I'm not really sure what you mean. Wouldn't a case structure be a solution?
Could you post some code so we can see what you are doing?
Best Regards
David
NISW
Message Edited by Davidek on 10-02-2009 09:58 AM
Message Edited by Davidek on 10-02-2009 10:00 AM

I have a for loop inside of while loop.when i press stop for while loop, i also would like to stop for loop.how can i solve this problem?thanks

i have a for loop inside of while loop.when i press stop for while loop, i also would like to stop for loop.how can i solve this problem?thanks

Hi fais,
Following through with what JB suggested. The steps involved in replacing the inner for loop with a while loop are outlined below.
You can replace the inner for loop with a while by doing the following.
1) Right-click of the for loop and select "Repalce" then navigate to the "while loop".
2) Make sure the tunnels you where indexing on with the for loop are still indexing.
3) Drop an "array size" node on your diagram. Wire the array that determines the number of iterations your for loop executes into this "array size".
4) Wire the output of the array size into the new while loop.
5) Set the condition terminal to "stop if true".
6)Drop an "OR" gate inside the while loop and wire its output to the while loops condition terminal.
7) C
reate a local of the boolean "stop" button, and wire it into one of the inputs of your OR gate. This will allow you to stop the inner loop.
8) Drop a "less than" node inside the inner while loop.
9) Wire your iteration count into the bottom input of the "less than".
10) Wire the count (see step 4 above) into the top input of the less than. This will stop the inner loop when ever the inner loop has processed the last element of your array.
Provided I have not mixed up my tops and bottoms this should accomplish the replacement.
I will let others explain how to takle this task using the "case solution".
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

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

While loop inside a timed loop

Hi everybody!
   I'm using:
       - LV 7.1 + RealTime;
       - compactFieldpoint;
   I've noticed a strange behaviour, when I put a while loop inside a timed loop. Let's fix timed loop with these settings:
       - 1 KHz clock
       - 1 ms period (yes, I know it's short....)
       - offset 0 ms
       - Phase 0
       - Discard missed period (ON) and MAintain original Phase (ON);
       - Timeout: -1.
   If inside this loo, I put a traditional while loop, waiting (say) for an event to occur, and if this event does not arrive, my cFP-2020 hangs! I mean, it becomes unreachable for the debugger, and, more, if I run a ping to it's address, after some cycles it becomes unreachable also from ping!
   Clearly, this code statement lock the fieldPoint, because if I remove the inner while loop all works.
I know that with 1 ms period, timed loop always finishes late, but I set to discard missed period and timeout to -1.
   It seems to me that sometimes Timed Loop add heavi overhead to programs, I'm turning to all while loop based tasks, even if my application has to be real-time!
   Advices welcomed! Have a nice day!
graziano
Solved!
Go to Solution.

I think the issue here is that putting your while loop inside a Timed Loop increases the priority for that task. Timed Loops can have dynamic priorities set over eachother, but they all run between Above Normal and Time Critical priority. My guess is that the debugger and built-in TCP functions run at Above Normal priority or less. This means your cFP isn't hanging, it's doing what it thinks is best. It's trying to finish this task before handling any lower-priority tasks.
The suggestion to put a Wait function in your loop is an OK one. Keep in mind that you can actually set your wait time to zero instead of one and get the same positive benefit of handling other tasks. I would also suggest that you might look into waiting for this event in a lower priority (non-Timed) loop, and then transmit the appropriate data to your Timed Loop using an RT-FIFO or something. That might give you better handling. Just a thought....
Jarrod S.
National Instruments

Timed loop in a subvi, one or the other runs but not both.

I have a vi with two sub vis. Each sub vi contains a timed loop that updates a global variable. In the top level vi I read from each global and display its content. When I run the top level vi I see only one global counting but not both. If I start and stop the top level vi the sub vis take turns counting but they never both count. If I replace the timed loop with a while loop in each subvi then both count. If I move the two timed loops from their respective sub vis and place them in the top level vi then both globals show counting. Can any body explain what is going on.
I'm using Labview 2010 SP1.
Attachments:
Test Of Timed Loop.zip ‏72 KB

Never Mind!
When I cloned the subvi I forgot to change the structure name of the timed loop. Placing an error indicator inside the subvi disclosed the error -808 (Error -808 occurred at an unidentified location. Possible reason(s):LabVIEW: The given name is already being used by the following timed structure.).

Minimise front panel of vi containing timed loop = problem

Is this expected behaviour...
Run the attached VI.
All it is supposed to do is beep every 10 cycles.
When you minimise it and try to restore the front panel though... it locks up for a random amount of time.
I don't think it is supposed to do that. (I'm running it on XP Pro.)
Originally I was chasing this problem in a data acquisition loop. The buffer would overflow and exit the app with an error when it was minimised.
It took all day to track it down to this.
Hmmm... I just tried to save it back to a version 8.0 vi and it doesn't seem to have the same error!
Message Edited by Troy K on 10-03-2008 05:26 PM
Message Edited by Troy K on 10-03-2008 05:31 PM
Troy
CLDEach snowflake in an avalanche pleads not guilty. - Stanislaw J. Lec
I haven't failed, I've found 10,000 ways that don't work - Thomas Edison
Beware of the man who won't be bothered with details. - William Feather
The greatest of faults is to be conscious of none. - Thomas Carlyle
Attachments:
Timed Loop minimised.vi ‏85 KB
minimisetimedloop.png ‏7 KB

I'm using LabVIEW 8.5.1 on two PCs and it does it on both of them.
I just emailed the vi to a colleague and after a few minimise/maximises it locked up on him too.
I've just found that if I remove the left and right data nodes inside the timed loop the bug seems to go away.
Steps to repeat bug:
1. Minimise all windows (Windows+m)
2. Restore vi front panel and run it. (It should start beeping twice a second)
3. Minimise / Restore it rapidly by repeatedly clicking on the vi's Front Panel 'task bar button' (down the bottom).
After a while the beeping will stop when the front panel is minimised and it wont restore. Then after a while (with or without clicking on the task bar button) the front panel will restore and the missed periods will execute very quickly (as the timed loop does what it is configured to do).
I think because of the simplicity of the example vi the bug doesn't show up as often. When I ran it in the real application (too many vi's to post) it crashed every time. In the real application there isn't much going on in the timed loop, it is just used to queue items into a separate consumer loop. The problem is that when the bug occurs, ALL LABVIEW CODE stops executing, not just the code inside the timed loop. So another vi running in parallel (in a daemon) that retrieves messages from a device queue stops and the device buffer overflows.
Attached is a modified vi to demonstrate that code outside the timed loop stops executing too. The bug occurs here on three different PCs, the only common thing I can think of is LabVIEW 8.5.1.
Troy
CLDEach snowflake in an avalanche pleads not guilty. - Stanislaw J. Lec
I haven't failed, I've found 10,000 ways that don't work - Thomas Edison
Beware of the man who won't be bothered with details. - William Feather
The greatest of faults is to be conscious of none. - Thomas Carlyle
Attachments:
Timed Loop minimised 2.vi ‏89 KB

Unable to click on buttons during timed loop .

Hi !
I have a timed loop with a cadence set by user . And when the loop is running, I can not push any button of my GUI to stop this....
I have to wait until error or I stop the run.
I can't put the diagram it's too big and I think I haven't the right but do you have some ideas ?
Ask me for more details .
Thanks
Solved!
Go to Solution.

bejard wrote: The Timed loop is just in an event structure and I set 10 ms or 100 ms .
The program is running correctly (with this Timed loop of 10ms/100 ms) as the beginning but I still can't push any button or change tabs during the loop .
You should not have long processes inside of an event case. What is supposed to stop your timed loop?
I think you have the "Lock front panel until event case completes" option turned on. This will not allow you to press anything until everything in that event case (including the timed loop) completes.
In my experience, using a timed loop in a Windows system is a complete waste and often adds more overhead and issues. Instead, I really think you need to change over to use a State Machine. When the button is pressed, you just tell your state machine to go into the state the runs some of the code inside of your timed loop. You can use the state with the event structure to time your loop. So you can go back and forth from your event structure state to your processing loop. Just set the timeout on the event structure to whatever loop rate you actually want.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Timed loop and CPU usage

Platform is WIN_XP Pro and machine is a P4 at 2.5Ghz with 512 Mb ram.
LV7.1 + PCI 6229
I am using 50ms Timed loop for running a state machine inside it
and also a whole lot of other things like reading / writing
DAQMx functions; file I/O functions and such. As the
project involves a main and sub-panlel set up local variables
could not be elimnated fully and there should be something like 150 of
them. But not all are accessed always - maybe about 15 of them at any
given time depending on the SM staus.
Problem :
Once started the "Finished late" indication is off and
the actual timing alternates between 49 to 52 ms. The CPU
usage is around 25%.
But as time goes by, the system gets unstable : After 15 minutes
or so, the Finished Late indication is always ON and the CPU usage is
gradually tending towards or exceeds 100%.
Obviously the machine control timing now gets affected and things slow
down badly. Closing the application ands restarting repeats the above
cycle.
I am at a loss to understand what is happening ? WIll
breaking down the single Timed Loop to multiple ones help ? WIll
that be an efficient way of parallel threading ?
I can post the code but its quite large and will do it as a last resort.
thanks
Raghunathan
Raghunathan
LV2012 to Automate Hydraulic Test rigs.

Hello,
It sounds like an interesting problem. It would be worth some experimentation to figure out what's going wrong - attempting to decouple major "pieces" of the code would be helpful. For example, you could try breaking your code into multiple loops if that makes sense in your architecture, but perhaps you could even eliminate all but one of the loops to begin with, and see if you can correlate the problem to the code in just one of your loops.
Another concern is that you mention using many local variables. Variable read operations cause new buffer allocations, so if you're passing arrays around that way, you could be hitting a problem of forcing your machine to perform many allocations and deallocations of memory. As arrays grow, this can be a bigger and bigger problem. You can use other techniques for passing data around your block diagram, such as dataflow if possible (just simple wires), or queues where dataflow can't dicatate program flow completely.
Hopefully looking into your code with the above considerations will lead you in the right direction. In your case, removing code so that you can identify which elements are causing the problem should help significantly.
Best Regards,
JLS
Best,
JLS
Sixclear

Questions about parallel and series sturcture in SCTL (single clock timed loop) in FPGA VI

I am using LV 8.2.
I have wriiten a FPGA VI, in this VI, there are 3 filters inside the SCTL (single clock timed loop) (I use the shift register to be the effect of unit delay). Would I save the resources of the FPGA used (such as slices and LUT) in the compliation report if I use 3 SCTL ( 1 SCTL contain 1 filter) and cascade them in series?
Thank you!

Sorry, I am afraid that you have misunderstood my meaning.
Here is the method you suggested before:
I mean I use the shift registers attached in the while loop, not in the SCTL. The number of shift registers used will not be decreased when we increase the number of SCTL in the second plate of the flat sequence structure. Totally , there are 6 pairs shift registers for 3 filters (1 filter needs 2 pairs). I mean I put the calculation parts, such as b0*x[n]+b1*x[n-1]+b2*x[n-2] inside the SCTL ( the operations of multiplication and add). Instead of putting 3 filters numeric operation part in one SCTL. will we reduce the resources used if we use 1 SCTL to do the operation parts of 1 filter? As the code inside each SCTL will be reduced.
Maybe you tell me if such approach will reduce the reosources used? Or there is no difference?
Thank you!

How do I break a for loop (inside) and a while loop (outside) at the same time by a control button

I have a while loop (outside) and a for loop (inside) and a control button within the for loop. I want to stop the program by click the botton without finishing the for loop. How can I do that?
Thank you in advance.

HI Please find attached snapshot Regards, Santosh
Message Edited by SanRac on 12-17-2009 05:12 AM
Message Edited by SanRac on 12-17-2009 05:13 AM
Attachments:
Snap1.png ‏4 KB

Stopping Timed Loop inside a Reentrant VI

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