Stopping output tasks properly before exiting a For-loop

Hi,
I've been having some trouble exiting a For-loop conditionally. The problem is that when the loop is stopped conditionally (a button is pressed) the DAQ (NI USB 6353) outputs get stuck to whatever value they were in. I tried stopping the DAQ Assistant output task (1 sample on demand) before exiting the loop but that didn't solve the problem. Should this perhaps be done one iteration before exiting the loop or can it be done in the same iteration round?
What would be the "right" way to exit a for loop with output tasks so that the output signals would be 0V after exiting? I know that I could "force" feed the DAQ Assistant with 0V control before exiting but in this case that would be quite difficult...
Any ideas? Help is appriciated.

Yes, I get it... However at this point I don't think that's an option.
Would this kind of solution work? ( I am not able to test all possible solutions in the real system which is why I would like to get a confirmation first)
The idea is to connect the output of the "Or" port to the "Stop" -ports of the DAQ Assistants in the loop.
Edit. Will the output automatically go to 0V if I just stop the task? I am not really sure about this.
Thank you.
Attachments:
exit-loop.jpg ‏8 KB

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Please remember to mark the replies as answers if they help and unmark them if they provide no help

Can I exit a FOR loop before it has completed its iterations?

Or is there a way to easily slave a while loop to an array input? I essentially need to search an array for a specific entry. Non of the built in VI's will search the array the way I need to do it. I tried wiring the array to a while loop and searching each element, but if the match is never found, the while loop never returns. Is there a setting on a while loop to force it to return if an input array completes?
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Hello –
I am attaching a very simple example program to show what Alberto and Dennis explained (or at least what I understood their approach would be, please apologize if I misunderstood).
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Attachments:
Example.vi ‏29 KB

How to output last 4 arrays from a For Loop?

Hi People,
I am almost at the end of my tether. I really hope someone could please help me.
Any input would be welcome. VI attached.
VI explanation:
I initialize an array.
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Attachments:
Help Understanding Arrays and file paths (10).vi ‏26 KB

Thanks so much Lennard!!
Hi JKSH,
I've been busy trying to complete the dang code, but for completeness so that other users can learn too, I shall answer your queries. Thanks for looking in.
First, what do you mean by "add"? Your code in your case strcuture sums your input values, so your array size doesn't change. However, you also said "Putting it outside the main For Loop with auto-indexing on gives me one file with all previous data. (This is not feasible as my number of shots should number in the thousands)" -- it sounds like you are expecting an array with thousands of elements. So, what should "Output Array N" look like?
Ans: Output Array N should be a 4x4 array of the summation of all the numbers generated during every 4th iteration.
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(Note: Most of your arrays are 4x4, but in Case #2 you created 128x128. I prersume this is a typo?)
Ans: Kind of, I'm using a 4x4 array of randomly generated numbers as an example but my actual data will be the 128x128 pixel output of a camera. And during actual experimentation, 'No of Iterations' will number in the thousands.
Second, why do you add your "simulated camera input" to the "Initialized Array"? You can add it direcly to the previous output inside your case structure.
Ans: See answer to question 3
Third, have a look at shift registers: http://www.ni.com/gettingstarted/labviewbasics/shiftregisters.htm. Use them instead of Feedback Nodes to make your code tidier.
Ans: I did try.. But I can't seem to add shift registers to the case structure, only the for loops outside. Are you sure it can be done..?
jaslyn wrote:
1) I would like to output only the last 4 sets of data from the Averaged Output 1, 2, 3 and 4 to 4 different files (i.e. save as .csv what is displayed onscreen in indicators 'Averaged Output 1', 2, 3 and 4 at the end of all iterations.
Where should I place my file save diagram disable so that it does this?
For the sake of fast camera capture, I would like these 4 files to only output once all the image captures are complete.
You will need to call "Write to Text File.vi" 4 times to write 4 files. So, you should finish your loop, then call this VI 4 times.
Ans: How do I get it to extract the data from each of the 4 cases in my case structure?
jaslyn wrote:
2) Would preferably like to name the file once and for the programme to append '(1)', '(2)', '(3)' and '(4)' to filename of the appropriate 'Averaged Output' Arrays but file path controls are another big headache for me.
You can create strings first, then convert them into paths: http://zone.ni.com/reference/en-XX/help/371361G-01/glang/string_to_path/
Thanks
jaslyn wrote:
3) P.s. is initializing one array enough to avoid using Memory Manager? Or should I initialize 4 arrays?
I'm not sure what you're asking; can you please clarify what you mean by "avoid using Memory Manager"? But anyway, you've actually initialized FIVE arrays: 1 outside the loop, and 1 inside each case.
I've read that to avoid fluctuations in memory usage, it is a good idea to initialize arrays to their expected size before the start of data collection. That was just what I was trying to do.

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altenbach wrote:
ceilingwalker wrote:
You are autoindexing way too many thing between the two FOR loops I was doing this to create a data dependency, at least that was my thought process behind it. As far as the physical channels and VISA refnums, I did it this way so I didn't create more controls for the front panel. Being my first project, I am very certain my logic is flawed, this is why I like posting here and getting feedback from
You have many visa sessions that (hopefully) never change during the execution of the loops, so why woold you turn them into an array of 11 identical elements just to autoidex them out again at the next loop. Change the tunnels to no autoindexing and things would look cleaner. Why are these session controls inside the loop? Are you expect them to be changeable during loop execution or would that screw up the results?
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Then show us what you tried! That should be trivial to implement. Why would a case structure affect performance? Makes no sense!
Why would a case structure affect performance? Makes no sense! I used a boolean operator to change the state. When I used a false, it worked for that problem but shut down my Vi before the second For Loop.
Wounld't it be easier to simply create an up&down ramp once and use a single FOR loop, autoindexing on the ramp? You have way too much duplicate code!!! I tried using one For Loop to begin with but because I had to ramp up, then ramp down, I couldn't figure out how to use just one. I needed an Add function for the ramp up and a Subtract function for the ramp down.
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RC4 Encryption beta.vi ‏78 KB

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Jim,
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James Morrison/Joan Lester wrote:
>
> Also remember you can make while loops auto index. Right pop on the tunnel
> and enable this and the loop will then act more like a for loop.
>
> Jim
>
> "Kevin B. Kent" wrote:
>
> > Mike Scirocco wrote:
> >
> > > I would like to know if it is possible to exit a For loop. I know
> > > I can use a while loop but it would be nice to be able to
> > > increment the loop counter in a for loop. Is this possible?
> > >
> > > Thanks,
> > > Mike
> >
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op.
> > Be aware that the loop will always run at least ONCE.
> >
> > A for loop will run X number of times. This is determined either
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> >
> > Kevin Kent

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Guided cal for loop.vi ‏27 KB

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Guided cal for loop.vi ‏28 KB

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Stopping output tasks properly before exiting a For-loop

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