Open and close visa inside a while loop

Hi,
I need to read a position from a control unit device continuously or even by click a button, for this I have to put "visa configure serial port" and" "visa close" inside a while loop. Dose it make any problem?

You shouldn't need the VISA Event nodes. Get rid of those.
Why are you using Concatinate String just to build up a constant. Just create a single string constant. It is a lot cleaner.
Is the antenna constantly sending data to you or only when you request it?
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Visa Open and Close on every iteration of loop

I have noticed that when you open the front panel of the Instrument I/O Assistant, the diagram starts with a visa session open, sets timeout property, writes, reads, parses data and ends with a visa session closed. If I were to place this into a while loop the visa session would open and close on each iteration of the loop.
Is it common practice to open and close the visa session on each iteration?

No you would not want to open and close that often. If you want to use the Instrument I/O assistant what I would do is configure it the way you want and then save it under another name so you can open the block diagram. Pull the VISA open and close outside of your loop.
Using LabVIEW 2010SP1 and TestStand 4.5

How do I open and close VIs from within a VI?

Ladies and gentlemen,
I would like to use a VI to open and close other VIs based on user input. Example: The first VI will have text that reads: "Does the car have heated mirrors?" There will be two buttons: one for "YES" and the other for "NO."
If the user hits the "NO" button, the current VI will close and a similar VI will open that asks the user the next question, "Are the mirrors lighted?" "YES" or "NO..."
If the user hits the "YES" button, the current VI will close and another will open that will tell the user to "Activate the heated mirrors" and press a button that will say "NEXT." At that point, that VI will close, and in two minutes another VI will open and ask the user "Is the driver's side mirror hot?" with another set of "Yes" or "No" buttons. If the user presses "YES" we will have verified that the heated driver's side mirror is working properly and store that information somewhere . If the user presses "NO", the VI will close and another VI will open with some kind of repair instruction and a button that says "RETEST" that will rerun the heated mirror test when repairs are completed.
During the two minutes we are waiting for the mirrors to heat up the program should move on to the next question: "Are the mirrors lighted?" "YES" or "NO..."
Does anyone know how to manipulate VIs in this way? Please help!
Drew

Instead of opening and closing vi's, just create one main vi with a state machine architecture. Search for examples on state machines to get a basic understanding of them. This is pretty complex so I have written an example of how this could be accomplished. The trick part was the 2 minute timer (my vi is set for 5 seconds for quick testing). Each state produces a question, and depending on the answer, the next state is inserted into a queue. You can add more states for more questions and answers. Notice that the boolean buttons can be hidden if you just want to show one button (like Next) instead of two buttons (Yes and No). Study the vi and let me know if you have questions.
- tbob
Inventor of the WORM Global
Attachments:
Q&A.vi ‏166 KB

How do I open and close vis programmatically?

I want to open and close a vi with a switch control. What is the best way to do this?

Probably the easiest way is to utilize vi server operations. Vi server will allow you to open a vi and close a vi programmatically. This is a great example that is built into LV. THis should give you some ideas. Hope this helps.
BJD1613
Lead Test Tools Development Engineer
Philips Respironics
Certified LV Architect / Instructor
Attachments:
VI_Server_-_Changing_Another_VI's_Properties.llb ‏625 KB

It's better or necessary open and close communication with instrument every loop?

I must communicate with my instrument, but I must change its value, for example temperature, every loop. See the Figure to understand:
I think that it is better if I open communication with my instrument out of while loop so I many operation: if I put Open VISA in While loop I open VISA session every loop, instead I think it is not intelligent. Can I open VISA SESSION out of the while loop or it is an error for EXCELLENT LABVIEW VI and I must open and close VISA SESSION every times I must talk (and set) with instrument? What is the better way?
Message Edited by Michelle1892773 on 02-22-2010 02:00 PM

Something like this?
I do have to say, i don't know what is happening in the false case of yours, but if nothing happens with the 100 that is wired to the shift register, once you enter the true case, the value in the shift register will always be great than "i". You might as well do what I have done then. However, if something does happen with that number in your false case, then keep it the way you have it.
That being said, why is the condition there to see if it has looped 100 times before doing the visa write??
Message Edited by for(imstuck) on 02-22-2010 04:45 PM
Message Edited by for(imstuck) on 02-22-2010 04:46 PM
CLA, LabVIEW Versions 2010-2013
Attachments:
visa.PNG ‏13 KB

My macbook is going to sleep while I'm working or viewing something. I will sometimes have to open and close it several times to get it to "wake up" again. Any suggestions?

my macbook is going to sleep while I'm working or viewing something. I will sometimes have to open and close it several times to get it to "wake up" again. Also, no sound comes out of my Macbook. I only hear with earbuds or headphones. Any suggestions?

If you have more than one user account, you must be logged in as an administrator to carry out these instructions.
Triple-click anywhere in the line below to select it:
syslog -k Sender kernel -k Message CSeq "Previous Shutdown" | tail | open -f -a TextEdit
Copy the selected text to the Clipboard (command-C).
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window (command-V).
The command may take a noticeable amount of time to run. Wait for a new line ending in a dollar sign (“$”) to appear.
A TextEdit window will open with the output of the command. Post the contents of that window, if any — the text, please, not a screenshot. The title of the window doesn't matter, and you don't need to post that.

Safari is slow to open and close. It also slows down other apps while running. Should I reload safari and if so, how do I do so?

Safari is slow to open and close. It also slows down other apps while it is running. How can I resolve this issue?

From the Safari menu bar, select
Safari ▹ Preferences ▹ Extensions
Turn all extensions OFF and test. If the problem is resolved, turn extensions back ON and then disable them one or a few at a time until you find the culprit.
If you wish, you may be able to salvage the malfunctioning extension by uninstalling and reinstalling it. That will revert its settings to the defaults.
If there's no improvement, continue as follows.
From the Safari menu bar, select
Safari ▹ Preferences... ▹ Privacy ▹ Remove All Website Data
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Open and Close OnScreen Keyboard while focus gain on JTextField

Hi
I have a Jtextfield when ever I click on textfield I want to open OSK(On Screen Keyboard) of Windows 8 OS and windows 7.
I tried in below mentioned way to open and close in focus listener focusGained() and focusLost() but it is not working. could some body do needful.
Opening OSK:
builder = new ProcessBuilder("cmd /c " + sysroot + " /System32/osk.exe");
Closing Osk:
Runtime.getRuntime().exec("taskkill /f /im osk.exe");

You need to start() the ProcessBuilder and you need to split the command like this:
builder = new ProcessBuilder("cmd", "/c", sysroot + " /System32/osk.exe");
builder.start();
And naturally you should wrap the call in a new Thread or use an ExecutorService to avoid EDT problems.

Main VI stops fucntioning after i open and close a subvi from an event structrue.

Hi,
I am trying to open a pop up vi from an event. I have been struggling with this for a while now. When i open a pop up vi and close it, the main vi stops running properly.
I have narrowed it down to the fact that the event which calls the subvi never finishes when the subvi is closed.
The attached image is an example of what I am currently doing. When I run this, i never see the dialog box that says 'here'
maybe useful as a hint to the problem...
This does work properly if I run the vi, click to open the subvi, close the subvi, (here the main vi is not working properly, cant click anything) then stop the main vi, run the main vi again, open and close the subvi, and then i see the 'here' dialog, and my main vi functions properly.
thanks
J
Solved!
Go to Solution.

What is actually happening is you hit the Ok button and your panel closes and you set the Stop 2 to True. Ok, that is fine except for the fact that the Stop 2 terminal has already been read during that iteration of the loop. So the loop will go again. This time is has read the Stop 2 at a TRUE, but the event structure needs an event before the loop can complete. But the front panel has been closed already and you are stuck.
As Dennis said, get rid of the Stop 2 and just wire the TRUE constant straight out of the event case. Wire a FALSE for all of the other event cases.
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Can we open and close the cursor again and again

hi all,
with the help of cursor select statement i am writing some columns into the text file. while writing into the file in between i want to write something which belongs to others cursor. shall i close the first cursor and reopen it again..
is its works?

If you are using for loop the you don't need to open and close the cursor like:
SQL> set autot off
SQL> begin
2     for i in (select ename, deptno, sal from emp)
3     loop
4             for j in (select dname from dept where deptno = i.deptno)
5             loop
6             dbms_output.put_line ('Ename:' || i.Ename ||' Dept Name:'|| j.dname);
7             end loop;
8     end loop;
9 end;
10 /
PL/SQL procedure successfully completed.
SQL> set serveroutput on
SQL> /
Ename:SCOTT Dept Name:RESEARCH
Ename:first_0 Dept Name:SALES
Ename:first_1 Dept Name:SALES
Ename:first_0 Dept Name:RESEARCH
Ename:first_1 Dept Name:SALES
Ename:first_0 Dept Name:SALES
Ename:first_1 Dept Name:ACCOUNTING
Ename:first_0 Dept Name:RESEARCH
Ename:first_1 Dept Name:ACCOUNTING
Ename:first_0 Dept Name:SALES
Ename:first_1 Dept Name:RESEARCH
Ename:first_0 Dept Name:SALES
Ename:first_1 Dept Name:RESEARCH
Ename:first_0 Dept Name:ACCOUNTING
PL/SQL procedure successfully completed.
SQL> Or let us know about your requirements i.e. why you need to open/close the cursor again and again.

Would you Open and Close DAQmx tasks within a function or Globally

Hi Guys,
This should start something.
The subject is DAQmx Tasks.
If you were writing a function that is called many times, say MeasureVolts (double *Value) to obtain a reading from an Analogue Input Channel.
Would you.
1. open and start the task inside the function, do the measurement and then close the task inside the same function.
or
2. open the task globally and later do the measurement inside the function using the global task then close the task only when the application is closed.
I am mostly concerned with the overhead of task generation and closing, what do you guys and girls out there do?? and what is the general opinion?
I would appreciate your views.
Regards
Paul.

I would definitely NOT keep configuring and clearing (I think that's what you mean by open and close) the same task over and over. I would configure once, read many times in my main app, then stop & clear once.
I typically like to package such data acq into an "Action Engine" that keeps track of its own DAQmx task id so I don't need to sling that task id wire around into multiple parallel loops / vi's. Attached is a very stripped-down example for Digital Input.
I would typically do more with error testing and would make the "Action" enum into a typedef custom control, but this gives you the basic idea. The action engine approach works very nicely when there's a small # of different kinds of input parameters and output info needed to support all the necessary action cases. When you start needing a large number of differnent kinds of inputs and outputs to support the desired actions, then you start having difficulty with (1) having enough terminals to wire and (2) remembering which inputs and outputs are meaningful for which actions.
-Kevin P.
Attachments:
DI Action Engine.vi ‏75 KB

Acquiring data from instruments and wiring it to a while loop

Hello,
I am very new to labVIEW and was thrown into a project. Essentially what I am trying to accomplish is to acquire data from my four sensors and use that data to compute drag. In order to compute the drag, an initial guess at what the drag is must be given and then calculations are carried out in a while loop that converges on a solution once the difference between the current drag output and the previous drag estimate falls below a certain percentage. I am continuously acquiring data so I need some sort of way to incoporate a timer to allow time for the while loop to converge and then output the drag value. Right now I am generating a signal since I do not have the sensors hooked up and labVIEW will not let me connect the signal generator to the while loop and gives me an error that I have connected two terminals of different types.
If I could figure out how to wire my DAQ assistants to the while loop I could figure everything else out
Thank You,
Ellen

Hi Ellen,
I might need a little more information before I can help you. How are you simulating your signals? If you're using the DAQ assistant express VI, are you simulating hardware in MAX? Or are you using the simulate signal express VI?
Alos, what VIs or functions do you have inside the while loop that you are trying to connect to?
Perhaps posting a screenshot would be useful. I'm sure we will be able to solve your problem.
Here is a help page that you might find useful.
http://zone.ni.com/devzone/cda/tut/p/id/4656
Joel G
Applications Engineer
National Instruments UK & Ireland

My apps dance open and close on their own in my IPad 2 what can be the prob? I have already restored

I got the charger flex or pin changed and now the apps dance on the screen, photos open and zoom in, then out, the other apps open and close. I have already restored the device with Itunes and prob is still there. What can be the problem? Any suggestion will be welcome. Thank you

THANKS for your prompt reply Bluetooth is off in my laptop and IPhone.. and in fact the reset is the only thing that can make it back to normal. But for a lil while. I wonder if it is the touch, or the home botton... both things are very expensive to replace, so I wouldn't like to spend $$ and continue having the prob.....

How can I enable the center mouse click to open and close tabs in Firefox and Chrome?

I have a MacBook Pro Model A1261 purchased in 2009. On my other mac at work (and my PC) I can center click to open a link in a new tab while in Chrome or FireFox, and also to close a tab by clicking on it in the tabs at the top. I am using an external USB mouse on my MacBook Pro and when I click the center scroll wheel it brings up the dashboard. I looked in the settings but wasn't able to find a way to change that setting for the center button to open and close tabs in my web browser. Is there a way? Please help!

You can restore the zoom feature by changing the values of the related prefs on the about:config page.
* browser.gesture.pinch.in -> cmd_fullZoomReduce
* browser.gesture.pinch.in.shift -> cmd_fullZoomReset
* browser.gesture.pinch.out -> cmd_fullZoomEnlarge
* browser.gesture.pinch.out.shift -> cmd_fullZoomReset
* browser.gesture.pinch.latched -> false
*http://kb.mozillazine.org/about:config
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Open and Close Front Panel of SubVI

Hi all,
Running LabVIEW 2011 on Windows 7 x64. I am trying to get a subVI front panel to open from my main FP with the press of a button and then close with a button press in the subVI. Here is the piece from my main FP that calls the VI and opens the FP
Plots is defined in another loop and all of the loops are in a flat sequence. I did it this way because I want it to start with the first press and not stop my main loop from running. I have moved the item in the left loop around a lot so I'm not sure if I can run that in the same loop as the event or not. Either way opening the VI seems to work fine.
The problem shows up when trying to close the subVI for the SECOND time. The code is here:
As I said, the first time I open and close the VI everything works as I expect it should. I am then able to open it again but now the "blank button" doesn't function and I can't close the window or even open the block diagram to probe anything. I have been trying to figure this out for awhile, any insite would be greatly appreciated!
Thanks
Solved!
Go to Solution.

Its good that you found the bug.
This code may serve as a way for you to compare notes.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Open and close visa inside a while loop

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