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urgent LED project

Hi all,


I want to change the string and update in my output while running the VI. Can any expert please help on this? Thanks.

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Message 1 of 12
  • Please use regular characters for file names. Your subVI does not open on english computers until it is renamed.
  • Why is this urgent? Is it homework due?
  • If you want to change the string during the run, the string needs to be inside the loop. Basic dataflow. Just use an event structure and use the timeout case to scroll the string and a value change event to change the boolean array according to the new string value. Do a few simple LabVIEW tutorials!
  • As a small tip, your scrolling code is extremely convoluted and inefficient. The following code does about the same things as yours. Of course there are many ways to do this. Also, your subVI only need one FOR loop. Right?


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Message 2 of 12

Hi @altenbach,

I'm a newbie and doing some self-learning on the Labview.

Thanks for your help. BTW, is it that my subVI need to be in the event structure as well?


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Message 3 of 12

yes, in the value change event for the string so you can create the new boolean array.

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Message 4 of 12

@altenbach wrote:
  • Please use regular characters for file names. Your subVI does not open on english computers until it is renamed.


     I believe that 子VI translates as "Child VI", or as we might say, "Sub-VI".  [That doesn't totally exhaust the Kanji that I recognize -- at one point, I could read at the third-grader level ...].


Bob Schor

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Message 5 of 12

Thanks, it does not really matter what it means, but if I double-click in in windows explorer (english), nothing seems to be happening. There seems to be some incompatibility.

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Message 6 of 12

OK, this was a little tricky, as I don't have LabVIEW 2017 installed anywhere except on a VM at work (installing it wrecked my two Windows 10 machines at home, but the rebuild made them "leaner and meaner", and I've been afraid to install it on my Windows 7 Work PC, hence the VM at work).  I renamed <Kanji-Child>VI to Child VI and put it in LED.


Sometimes it is helpful to explain what you are trying to accomplish, otherwise we have to guess.  It looks to me like you are trying to make a "Moving Alpha Display Using LEDs", with Child VI taking a string and returning a (vertically)-concatenated 10x11 array of Booleans for a few Roman letters (specifically the letters N, I, R, O, C, K, and S).  As Altenbach notes, this is done using two For Loops, one to get a letter at a time, the other to encode one letter -- both can (and probably should) be done in the same loop.


The array that comes out is not easily read, as it goes down.  If you output the transpose of the array, you get a more-expected horizontal string of letters (the encoding array has the pixels of the letters "on their side", so transposing things puts the top row of letter pixels in Row 1 (where it belongs) instead of in column 1.


I'm not certain I understand the intent of the main LED routine.  Here is where an explanation would be handy.


As LED is written, it calls Child VI once with a specific String, Child VI returns the LED Pixel array, then you "do something" with the returned array.  Did you want to be able to start and stop the display?  Did you want to be able to display arbitrary text?  How did you want to change (or start) the Display?  What causes the program to stop?


It is often a good idea to think about what you want your program to do, and to write 3-5 sentences that "tell the story" (no code yet).  Once you know what you want to do, you can begin to think "How can I do that in LabVIEW?" , or "in C++", or "in Matlab", or whatever.  For example, if you wanted to enter a String and have that be the "new" displayed String, you might think "Ah, how about a Producer/Consumer loop, with the Producer being an Event Structure that "fires" when I enter a String?".


Bob Schor

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Message 7 of 12

can you post the VI in labVIEW 2015 format pls ?

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Message 8 of 12

But I still cant change the string while running the VICapture.PNG

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Message 9 of 12

It's still not working, VI as belowCapture.PNG

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Message 10 of 12