Problems with opening file with while loop

Greetings everyone,
This is probably a quick question, but I am familiarizing myself how to open data files in Labview. The attached code works if you enter a file from the folder button on the front panel. However, if the path is blank and you hit the run (arrow) button, a dialog box comes up and asks for the file.
I select the file, but the dialog box keeps coming up. I think this has something to do with my while loop. Can anyone tell me where I am going wrong?
Thanks!
TheLT
Solved!
Go to Solution.
Attachments:
ReadingfromData.vi ‏27 KB

TheLT,
1. crossrulz was right. The Read FromSpreadsheet File.vi opens and closes the file each time it is called. If no file path is present at the input when it is called, it will pop up a file dialog.
2. LabVIEW uses a dataflow paradigm. In your program the effect of this is that the File path control is read almost immediately when the program is started and never again after that. So, if the program is already running when the file is selected in that control, the new value is never read and the value (empty) in the control when the rpogram started is used.
3. The fix is to use an event structure with a file path Value Changed event to detect when the control has a value entered and then read the file.
4. Sequence structures obscure code, make it difficult to modify and extend code, and can almost always be eliminated by effective use of dataflow. Local variables should not be used just to pass data around. Wire is always the best way when possible. In your program adding a few wires allows elimination of the sequence structure and the local variables.
5. Your graph loop should have some kind of delay or wait. No need for it to run as fast as the processor will allow - and to hog all the CPU time - to repeatedly put the same data onto the graph. This is another place where an event structure is appropriate. Only update the graph when the X-Axis or Y-Axis selections have changed. Note: Accepted best practice is to use only one event structure in a program, although there are a few advanced cases where multiple event structures are appropriate. You only need one.
6. If the slected file does not contain the "endheader" string, the program will never stop. Add a test for EOF to stop the program if the End of File is reached without finding the flag.
Lynn
Attachments:
ReadingfromData.2.vi ‏27 KB

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Time not stopping with while loop

Hello,
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Attachments:
timing.vi ‏15 KB

One of the problems is that your VI is not able to "breathe" because it is sometimes trapped inside inner loops that consume all CPU and step on each others toes. All you need is an single outer loop and a few shift registers.
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LabVIEW Champion . Do more with less code and in less time .
Attachments:
timingMODCA.vi ‏15 KB

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Message Edited by altenbach on 04-26-2006 01:25 PM
LabVIEW Champion . Do more with less code and in less time .
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Timing with while loop

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while- loop.GIF ‏6 KB

nichts wrote:
Hello,
How can I do a time with while loop?. I want to read a data in the While- Loop for 1 sec and then go to B .. I added a pic,
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Solved!
Go to Solution.
Attachments:
Control Interface.zip ‏61 KB

Hi NitzZ,
Thank you for your reply.
I tried to save the VIs in LV10, please tell me if you can open them now.
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Maybe "refnum", but I don't really understand how to use them...
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Attachments:
Control Interface.zip ‏104 KB

Noob Help with While Loop

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Problem with one loop in another one

When I drag and move cursor, X scale position will be show below. And then I click “add data in array”, the data should be put into array. I can move cursor again to add the second , the third ….into array.
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Attachments:
yxxx.vi ‏29 KB

Hey, no need to make it so complicated. Just add an indicator on the CursLoc.X wire in the "0 To 5 MHz": Cursor Move case.
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Message Edited by jasonhill on 04-07-2006 12:40 PM
Attachments:
cursor position indicator.PNG ‏7 KB

Help needed with while loops please :)

I'm beginning to study java at School.
My assignment using while loops, to ask user to input 2 numbers.
I have to output all odd number between the two.
I have to output the sum of all even numbers between the two.
Output all the numbers and their squares between 1-10.
Output the squares of the odd numbers between the 2 numbers the user entered.
Output all uppercase letters.
If anyone can give me any help, I would appreciate it greatly.
Thank you.
Kelly.

It would help if you put aside your code, and wrote out some pseudo-code first so that you understand the steps you will need to take. for example
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Problems with opening file with while loop

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