Programmatically redirect shared variables

I can programmatically change the data binding for a shared variable from (from on RT target to another) using method 1 as described here:
http://digital.ni.com/public.nsf/allkb/2E8BAD0EA218A7558625712E0003F044
However the change is only associated locally with the current VI, if I restart the VI or access the shared variable from a different VI it returns to the initial data binding as defined in the variable library. I have to change the binding each time a start a VI.
Is there a way to programmatically change the data binding in such a way that the change is persistent and shared between vi's?

Hi PESobol,
when you want to store changes you actually need to store them!
You can access shared variables programmatically using functions like "Open Variable connection". So you could load a text file with descriptions of your shared variables and connect to such a variable based on information of the text file. For me that seems like a better way of configuration than having to change and save VIs all the time…
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Similar Messages

Data Logging a programmatically created shared variable of cluster or array datatype into citadel DB

Hi,
Is there a way to log a programmatically created shared variable of cluster or array datatype into citadel DB?
I have attempted to programmatically create a shared variable of type 'double' and was able to successfully log the same into Citadel DB. In the attachment, Please refer to the attached project SV_TC.lvproj and specifically to SV_W.vi for the code that i have used (W.png file shows the dB in MAX and shared variable in NI Distributed System Manager)
However when i tried the same approach to create a shared variable 'array of double', i noticed that traces are not getting created and hence data logging isn't happening into the Citadel DB. I was however able to write and read the shared variable array without issues. The same is true with cluster datatype also. Please refer to SN_NW.vi for the code that i have used - only difference from SV_W.vi is that i have tried to create a shared variable of type 'array of double'
One observation is that if i create an 'array of double' or cluster in a shared variable library using the project explorer and deploy, i could see that these being logged into Citadel DB.
Hence i want to understand what could be done to achieve the same programmatically? Could you please advice?
Regards,
Sridhar
Attachments:
SV_TC.zip ‏3925 KB

Why is the transaction happening over remote?
Because we need the information to be on our database immediately when they submit it.
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The web database is run by the company that hosts our web site. We use PL/SQL to show the pages and output the html. It fetches the data the customer is requesting from our database, but I'm struggling to get the best way to insert into our database from there.

Programmatically deploying WSN node shared variables

I'm working on a WSN network composed by one WSN9791 gateway, eight WSN3202 programmable remote nodes and one PC with LabView.2013. The nodes are programmed to get some voltage readings and store them in shared variables. My main application is running on a PC, it basically reads the global variables values and performs other processing.
Before running the main application I give the command "Deploy All" by right-clicking on the gateway name. I can do the same by right-clicking on each node and selecting "Deploy".
Some weeks ago, due to a thunderstorm, the power to the entire system was lost and, after automatic restart, my application was no longer able to contact the shared variables and I had to manually repeat the "Deploy" sequence.
My question is: "is there any way to programmatically deploy/undeploy shared variables"?
Note that in my application I access the nodes shared variables by opening a connection to the variable and then reading its value (see attachment 1) instead of using explicit connections to variables (see attachment 2).

Hi,
this is done on your block diagram using an Invoke Node. Go to your functions palette on your block diagram and go to Programming>>Application>>Invoke Node. Then left-click the Method of the Invoke Node and go to Library and select the desired command. It is important to note that you cannot deploy single variables at a time, you can only deploy variable libraries at a time.
I also think that the following article will help you understand better the process of using shared variables in LabVIEW. I referenced it while I was researching your questions.
Using the LabVIEW Shared Variable: http://www.ni.com/white-paper/4679/en

Why should you explicitly open and close shared variable connections?

I'm looking into switching over from the old Datasocket API to the new Shared Variable API for programmatic access to shared variables, and I noticed that LV doesn't seem to have any problems executing Shared Variable Reads & Writes without first opening the connection explicitly. That is, I can just drop in a shared varaible Read VI, wire a constant to the refnum input, and it will work. I'm wondering, then, what benefits are offered by explicitly opening the conenction ahead of time...?
I guess I could see some cases where you want to open all necessary connections in an initialization state of a top-level state machine, particularly if you want to use the "Open & Verify Connection"---so you could jump straight to an error case if any connections fail. But other than that, why else might one want to explicitly open the connections.
And, along those lines, are there any problems with implicitly opening the connections? One reason why I am hesitant to open them explicitly is because for one of our applications, we need to be able to dynamically switch from one variable to another at runtime. It would be nice to just switch the variable refnum (wired to the input of the Read function), without having to manually close out the old connection and open a new one. A quick prototype of this seems to work. But am I shooting myself in the foot by doing so?
Thanks in advance.

I'd expect there's a very small number of people at NI that would know the answer to the detail you're asking for. But, let's try to extrapolate from this rather old post to see if we can understand what they're forming their impression on.
The shared variable has to have some sort of reference going on in the background. It looks like they're calling this a connection. It's how LabVIEW knows where to find this variable on the network. We can also see this reference certainly exists if we're opening/closing the reference in the explicit method. You see the connection as just a string referencing the variable by URL. This "reference" has to be stored somewhere. No matter how we're looking at this, we're aware there's a reference of some sort stored.
Now, we'd want to look at what would cause this reference to go away. If you open/close explicitly, it's easy to see it goes away at the close. If it's implicit, when would it make sense to close it out? The VI can't be expected to guess where it's done being referenced and close it out. This puts us into a situation where the soonest it could close is when the VI ends. From my experience, references tend to be wiped when you close out LabVIEW. It's this kind of idea that makes the FGV possible. I wouldn't be surprised by Morgan's claim here.
If we look at scalability, you're talking about two different topics. You're talking about adding an extra open, close, read, etc rather than just a few wires. That certainly would look a mess. In terms of the dynamic swap that was being discussed, we wouldn't be adding all of those. The concern would be if enough connections were opened it'd start to behave similar to a memory leak. This could be something that works with a smaller number of variables. If you continue to scale, it becomes problematic. This is why they suggest it's not scalable.
To your questions:
Does LV allocate some kind of session in memory using that string as a lookup?
It would HAVE to allocate some memory to hold that string. Otherwise, it'd be pointless to even have the reference.
Does it reuse that session if other parts of the application reference the same variable, or does it create a unique session for each referencing call to "Read Variable.vi"?
I would expect this to be "it depends." With the implicit method, I would expect it to open a new reference in each point it isn't wired. This is similar to int x,y = 5; x and y share the same value but are their own unique memory location. If you wire the reference to the other points, it should use the same reference. This would make more sense to me than the program seeking out any other potential usage of the variable in the application to see if there's already a reference open. I could be wrong, though.
And what resources does this "connection" actually represent?
At best, this is just the string. At worst, it's the string and the TCP socket. I'd lean towards the first. Opening and closing sockets should be relatively easy in most applications. But, it also wouldn't surprise me if it holds the socket.
I'm sure others have a better understanding than I do. But, that's what I'd expect for anything you've asked.

Binding shared variable in executable across network

I can't seem to get a shared variable to bind from an executable on another computer back to a source variable on the main machine.
I can get the remote variable to change with programmatic access. Is it possible to have shared variables in an executable bind to a PSP URL on another computer? This is labview 2011.
I can see everything with NI Distributed System Manager, and the programmatic access changes the remote variable, so it's not a network issue.
Thanks for any insights. This just doesn't seem to work the way NI's online white papers say it shoud.

What I don't understand is why after binding to a specific URL, the "Shared Variable Deployment" screen of the application builder makes the target "my computer".
I probably could get this to work if I changed the network address of "my computer" in the ini file created in Application Builder?
This seem a strange way for this binding process to work. If the absolute target (for shared variable bound to another variable and referencing "absolute") was retained when the VI goes through the application builder, it would make for sense.
I can't get this to work any way with using bound variables. The only way this works is using programmatic access to shared variables in the built app, and I don't consider this the same thing.
My conclusion is that shared variable binding and appropriate absolute references to deployed variable libraries do not survive passing through the application builder with their absolute references intact.

Binding Shared Variable to Source

Dear all,
I'm currently working on a project that requires the use of shared variables. The shared variables will be network published and programmatically created using properties nodes. However I encounter one error and one problem in the process of doing so.
1) I programmatically bind the shared variable directly to the fieldpoint channel (data item) by writing the URL \\10.0.0.1\FP\1AIO\00 when i create the shared variable. The shared variable can be created successfully but when i deploy it, it generates an error which seems to tell me "it is out of range". Can anyone help me to rectify this problem?
2) The 2nd question will be, as my fieldpoint is connected to a DHCP server. At the start when i create the shared variable programmatically, i could bind the shared variable directly to the data item by writing the URL to its property. However, during the process of deployment, the dynamic IP address assigned to my fieldpoint may change . How can I ensure that the shared variable continue to bind to the right fieldpoint channels respectively? even though the IP address changes?
- Or is there any method that I could view all the network data items in a table? a list? or an array? so that I can link them to the URL.
I tried using the data socket URL.vi, I can only select the data item one by one.. this will be tedious for 100 or 200 I/O points..
Will greatly appreciate for any advice and help. Thanks in advance.

Try this.
Give your fieldpoint controller a computer name through MAX. Then instead of referencing it by 10.0.0.1 in the URL's of the shared variables reference it by computer name. So \\MyFPmachine\FP\1AIO\00 instead of \\10.0.0.1\FP\1AIO\00.
Dynamic IP's can definitely cause headaches, and it would be best to use static IP's if possible, but doing this method should help. It seemed to work for me. I found when you browse for the channel in LV, it wants to give it the IP address by default, but it was possible to edit the string and paste in the computer name.
Message Edited by Ravens Fan on 01-10-2007 11:01 AM

Enable shared variable buffer

Dear all,
I'm writing on a program to create shared variables programmatically. I use the examples available in labview and DSC 8.0 as reference. I'm able to create and set the different properties such as scaling, alarms, inital value etc for the shared variable(s). However, when i wire a boolean "true" to " enable buffering", it doesnt seems to work. I checked the shared variable created in the shared variable engine, the variable is created but the buffering cant be enabled programmatically. Can anyone guide me what's the fault? thanks.

Hi,
The VI worked without any problem though I had to change the shared variable name. One thing to note about changing the properties of shared variables programmatically using the shared variable I/O is that it only affects the deployed shared variables and not the actual library file. In essence, these changes are not saved in the library. So the shared variable properties window will not reflect the current status of the "Network.UseBuffering" option. To verify that the "use buffering" is enabled, place another "Network.UseBuffering" property node on the block diagram and read the current state from it.
Attached is a modified version of the VI with the current status of the "Network.UseBuffering" property for the deployed shared variable.
Tunde
Message Edited by Tunde A on 03-05-2007 12:34 PM
Attachments:
Modified_buffering_error.vi ‏10 KB

How to add a new Shared Variable programmatically to an existing and deployed library?

Hi there!
I am trying to accomplish this on both LabVIEW 8.6 and LabVIEW 2010 and seems like it's not any different in this situation.
My case: A project has a library with 4 Shared Variables (SVs). The library and the variables are deployed (visible in Distributed System Manager 8.6/2010). I want to add 2 more variables into this library. It is possible to do this manually from Project Explorer window's options menu. But while running an application it has to be done programmatically. Can I provide the library reference to the one currently existing without creating a new one?
"Create Or Add Library To Project" function in the Datalogging and Supervisory Control (DSC) toolkit does not help in this case. That function, as the name suggests, just tries to create a new library in the project.
Two possible methods:
The function "Add Shared Variable To Library" (DSC>EngineControl>Libraries & Processes) needs a library reference, which could be provided via "CreateOrAddLibraryToProject" function, but this function tries to create a new library, and if I provide the path of the existing library it throws an exception that the library already exists in the project (yes, as I wrote above, I need to add new variables to an existing and deployed library).
OR
The function "Create Shared Variable" (DSC>EngineControl>Variables & I/O Servers) will add Shared Variable in a process, and not physically in a library file, and the problem (limitation) with this approach is that it doesn't allow to add complex data type Shared Variables (for example in LabVIEW 8.6 it has only 4 datatype options in input parameter, and even in LV2010 it does not have "Image" datatype that I need).
The scond method is my preferred method as it allows to work on Online Shared Variables and doesn't create them physically in libraries (and this is good as the variables' scope remains only till the Variable Engine is running). But it doesn't support advanced data types, and the first method is powerful in terms that it supports to virtually any datatype, it just seems tricky to get that reference to the library.
Any tips?
Thanks ahead!
Vaibhav

<<<<>>>>
As the above two images show, while a library does not exist, it is easy to use the "CreateOrAddLibraryToProject.vi" which will add a new library to the project (if it doesn't exist on file system, a new library will be created) and that way, using the reference (the green wire going out from the function and the Case Structure, can be used to add Shared Variables to the library. The problem was what to do when a library already exists in the project, how to add more variables to it. I was looking for a way to get a library reference, and somehow I could not see it inside a Project's property (VI Server functions). Hence I posted the question. And upon continuing my search, I found it on the Application's property list.
I hope it was useful for someone else as well. And thanks for the replies. Please share a better idea if you have.
Vaibhav

Error programmatically deploying shared variable lvlib from an installed app

I'm using shared variables in my app. According to what I've read, I need to deploy the lib programmatically using the app invoke node deploy library. I do this and it works fine for the app exe on my machine. But then I created an installer and tried it on a "virgin" machine and I get a "error 1 at invoke node" saying "an input parameter is invalid." I added an indicator that shows the lib file path I'm using and it's fine. I had left the target IP addr unwired but I also tried 127.0.0.1 just in case. Any ideas what's going wrong here?

Hi:
If including the SVE installer didn't resolve the issue then it looks like there are some other possibilities that are discussed in the following forum threads. Not sure if you've seen these yet, but hopefully they will help.
http://forums.ni.com/ni/board/message?board.id=170&message.id=240865
http://forums.ni.com/ni/board/message?board.id=170&message.id=230033
http://forums.ni.com/ni/board/message?board.id=170&message.id=249345
Message Edited by A Person on 03-23-2009 02:40 PM
Message Edited by A Person on 03-23-2009 02:40 PM
Alex Person
NI-RIO Product Support Engineer
National Instruments

Shared Variable Alias vs Programmatic Assignment, which is better?

Hello,
I am programming an application for a cRIO platform using the scan engine in LV2009SP1. I'd like to use the cRIO as a standalone controller, and only connect a computer to it occasionally to download data. I decided to do this using shared variables. So far I've been successful at doing this in two ways, both involved creating nearly identical sets of shared variables on the cRIO and on the PC, which I think (correct me if I'm wrong) I understand is the way it should be done. The differences are the following:
The first method was to create a parallel loop on the RT VI which would assign the values passed through the shared variables to the individual I/O channels.
The second method was to Enable Aliasing on each shared variable and bind it to the appropriate I/O channel.
After deploying the RT code to the cRIO for each case and running the UI on the PC, I noticed that both worked, however, the second method showed a short lag between command and feedback (~200ms or so). The test I ran was to wire an analog output to an analog input, command the AO, and read back the value on the AI. I can deal with the delay on the UI since it's only for reference - what I'm really interested in is the data that's logged on the cRIO controller. My question is: Is one of the two methods better or more appropriate than the other? Is there something even better?
Thanks,
-NS

No Substitute wrote:
I decided to do this using shared variables. So far I've been successful at doing this in two ways, both involved creating nearly identical sets of shared variables on the cRIO and on the PC, which I think (correct me if I'm wrong) I understand is the way it should be done.
Hi NS,
No correction necessary. These are both valid ways of sharing data between your Real-Time controller and your PC. Here's a forum that discusses some similar options to accomplish the same task (
Shared variable architecture for distributed crio system)
Regarding the latency issue with method 2, take a look at KnowledgeBase: Why Is Accessing IO Variables Through The Shared Variable Interface So Slow?
I hope this helps!
- Greg J
Why Is Accessing IO Variables Through The Shared Variable Interface So Slow?

Re: shared variable: create programmatically then read/write

I programatically create and destroy Shared Variables using these subVIs (see enclose llb file for Add Variable Connection.vi and Delete Variable Connection.vi). But it seems to take a long time to run each subVI. This might be tolerable for a single Shared Variable, but it gets rather lengthy if several need to be created or destroyed. The user specifies how many depending on how they are using the application. Is there a more efficient way of doing this?
Also, after a Share Variable is "created," it can take a while before it is usable for reading and writing in another part of the application. Is there a way to determine a Share Variable is ready prior to using Search Variable Container and Open Variable Connection functions to find and use it?

Ummm, nothing attached. Also mention, when you do post, what version so that people won't waste time downloading when they don't have the appropriate version installed.
Putnam
Certified LabVIEW Developer
Senior Test Engineer
Currently using LV 6.1-LabVIEW 2012, RT8.5
LabVIEW Champion

Programmatically bind shared variable

Hi,
I'm trying to bind a control to a shared variable, if I clic on properties=>Data Binding, everything is set up correctly, but I get a red flag. Then if I add a white space after the variable path then clic OK. everything is fine and working properly.
My problem is I have to bind hundreds of shared variables so I don't want to modify every single control properties...
Anyone has any clue on what's happening?
Rodéric L
Certified LabVIEW Architect
Attachments:
properties.JPG ‏34 KB
method.JPG ‏18 KB

Looking at some similar code that I had developed to set FP bindings, I included single quotes in the url, for example:
\\My Computer\IO\'PU.Heater_Power'
Maybe the space is satisfying the need for a delimiter of some sort?

Error -1950678991 saving LV8.2 library of shared variables

I used to be able to programmatically save my library of shared variables using "ProcessToLib.vi" (set to Process mode) after changing properties of some or all variables. Now, and I don't know what has changed, I get this error:
Error -1950678991 occurred at property node (arg 1) in NI_Variable.lvlib: SetRawCluster.vi -> PRC_SVsToLib.vi -> PRC_DumpProcess.vi -> ProcessToLib.vi.
The explanation suggests that an Engineering Full Scale is the same as an Engineering Zero Scale value, but I have checked all variables that use scaling (not all do) and I can't find any such fault. Since these low-level VIs have protected diagrams, I can't trace the source of the error. I have tried the same thing on other libraries and they work fine.
I have attached my library for anyone to verify or duplicate the problem and maybe find out what is causing this error.
I have recently installed the DSC patch, but this should not be related to the problem.
Thanks,
Mike
UK
Attachments:
Krystallon Variables.lvlib ‏142 KB

Hi Mike,
I think something has become corrupted in your library. When getting the names of all the shared programatically I get multiple entries for a couple of the X-GPS variables. I deleted all the X-GPS variables and WS-116 and it saves fine. I think you might need to delete and recreate these variables.
Regards
Jon B
Applications Engineer
NI UK & Ireland

Shared Variables - Properties

Hello,
I have a couple of questions about properties of Shared Variables (SV). They can be configured either by using the dialog box (right-click on SV -> Properties), or programmatically via the "SharedVariableIO" property node. Have a look at the NI-Examples to see how SV can be created programmatically by using the DSC module.
1) The dialog box offers a property "Variable Type" which can be "Network-published", "Single-Process" or "Time-Triggered". The "SharedVariableIO" property node gives no access to this property. Does anybody know why? The same question can be rephrased: How can I create a "Single-Process" SV programmatically?
2) The "SharedVariableIO" property node has two items, "Network.OnScan" and "Network.ConnectionType", which have no direct correspondance to any of the properties available in the dialog box. What is the exact meaning of those properties? The on-line help isn't of much use here...
3) Mutliple SV can be edited by using the Multiple Variable Editor (Tools->Shared Varaible->Multiple Variable Editor). A cool feature is the import/export of CSV-files. I am interested in programmatically creating SVs from the information stored in such a CSV-file. Reading the file is no problem, but connecting the file entries to the properties of the "SharedVariableIO" property node would be quite some job. In principle NI has already solved that within the Multiple Variable Editor. I guess there is a bunch of VIs somewhere below "....Program Files/NI/.../vi.lib that do exactly this thing. Does anybody know, if these (which ones?) are available for public use?
Regards,
Dietrich

dietrich wrote:
1) The dialog box offers a property "Variable Type" which can be "Network-published", "Single-Process" or "Time-Triggered". The "SharedVariableIO" property node gives no access to this property. Does anybody know why? The same question can be rephrased: How can I create a "Single-Process" SV programmatically?
You can't. The single-process shared variable is an old style LabVIEW global placed under the shared variable abstraction. There is currently no way to create those on the fly. Time-triggered also cannot be created programmatically. I confess I don't know enough about them to know the reason why.
dietrich wrote:
2) The "SharedVariableIO" property node has two items, "Network.OnScan" and "Network.ConnectionType", which have no direct correspondance to any of the properties available in the dialog box. What is the exact meaning of those properties? The on-line help isn't of much use here...
Network.On Scan = read/write hardware? - this allows you to programmatically control when you are reading from or writing to configured hardware.
Network.ConnectionType = connect to hardware even when no one is viewing me? - this has 2 choices, UpFront & OnDemand, UpFront means that the variable will be connected to hardware even when no one is connected to the variable. This is useful when you want to reserve hardware or when logging is enabled. OnDemand means that you disconnect from hardware whenever no one is reading the variable.
dietrich wrote:
3) Mutliple SV can be edited by using the Multiple Variable Editor (Tools->Shared Varaible->Multiple Variable Editor). A cool feature is the import/export of CSV-files. I am interested in programmatically creating SVs from the information stored in such a CSV-file. Reading the file is no problem, but connecting the file entries to the properties of the "SharedVariableIO" property node would be quite some job. In principle NI has already solved that within the Multiple Variable Editor. I guess there is a bunch of VIs somewhere below "....Program Files/NI/.../vi.lib that do exactly this thing. Does anybody know, if these (which ones?) are available for public use?
I would advise against using any of these. National Instruments can change, or remove, those underlying files at any time as a result of modifications to the MVE. That could cause issues for any code using those sub-VIs.
Regards,
Robert

DSC: Importing Shared Variables results in error -1950679010

This post is more of an "FYI" rather than a question. I am using LV DSC 8.2.
ASIDE: I ran into this problem because I was trying to solve a related problem with Deploy Library.vi (I had dependant libraries that deployed manually, but not programmatically). Eventually, I found the answer in http://digital.ni.com/public.nsf/allkb/8EF71E1DDDC36C908625716900594B50 (not a very satisfactory answer however, IMHO).
During my solution search, another hint was provided with http://forums.ni.com/ni/board/message?board.id=170&message.id=177268&requireLogin=False which hints that using a "Network" defined SV, as opposed to a "Project" defined SV, could help. Then I discovered the difference between NetworkrojectPath and Network:URL in the SV property definition. Then I realized that NetworkrojectBinding is exposed in the Import fields (using the Multiple Variable Editor to do the importing of course), and this gave me the idea of being able to define a Network SV using the Import function.
Unfortunately, it does not work. In the csv file I set NetworkrojectBinding to FALSE, Network:UseBinding to TRUE and provide a valid Network SV path, but this results in error -1950679010: "Shared variable is bound but path or URL is not specified", which occurs when trying to save the LVLIB. It would be nice to know why this doesn't work, as I think it should. I think it is a problem with the SV import mechanism.
David Moerman
TruView Technology Integration Ltd.

Yes, you can do this programatically. I've attached a small chunk of example code (LV 8.5) that creates just 1 variable, as well as an image of it in case you are using an earlier version of LV. If you want to create multiple variables for the same library just put the "AddSharedVariableToLibrary" in a loop, of course.
David Moerman
Attachments:
Create Library and SV.PNG ‏48 KB
Create Library of SVs - BASIC.vi ‏24 KB

Programmat​ically redirect shared variables

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Programmatically redirect shared variables