Shared variable, bind to source

I have two projects, one on a computer the other on a FieldPoint. The computer is the client.
If I bind a shared variable on the computer to a shared variable on the
FieldPoint (Bind to source), what protocol does the communication use?
NI-PSP?

Hi,
Every Shared Variable is transported via the NI-PSP protocol. The NI-PSP protocol is based on the UDP. More information about the NI-PSP you can find at http://zone.ni.com/devzone/cda/tut/p/id/4679.
hth
Joachim

Similar Messages

Touch Panel Shared variable binding does not work.

Hi,
Is there any reason why shared variable binding is not working under Touch Panel Target?
Is there any plan for implementing or there is some trick I should know?
Andras

RebeccaFo wrote:
Hello Andras,
which version of LabVIEW are you using? As yu can see in:
http://digital.ni.com/public.nsf/websearch/04AAA6903A9456F08625715A0026BC57?OpenDocument
it should work. So what for problems do you have?
Thanks,
Just FYI, the KnowledgeBase article linked above has been revised and moved to a new location. See the new KnowledgeBase 58JFBGD2: Are Shared Variables Available For LabVIEW Mobile Module (Formerly PDA Modul...

Error -1950679007 when I try to create shared variable binding automatically

Hi All,
I'm using LV 8.5 with DSC.
My aim is build shared variable library automatically. A program read variable name, data type and network binding address from .CSV file. Program works well untill I add this "bind to source" property. I don't know what goes wrong. Does anyone else have found this same issue?
Picture about problem is in attachment.
The error codes are found here:
http://zone.ni.com/reference/en-XX/help/371361D-01/lverror/shared_variable_error_codes/
Other useful information:
http://digital.ni.com/public.nsf/websearch/2E8BAD0EA218A7558625712E0003F044?OpenDocument
Thanks,
Attachments:
error_19506790071.jpg ‏88 KB

Hi,
Now i able to attach the file, While creating Shared Variable,Enable the options which i given in the image by same order. So i think it will solve this problem. If it cont., i will give some more suggestion.
With Regards,
vijay_Conz
Attachments:
Creating SV lib.JPG ‏28 KB

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.

Bind shared variable to multi-channel item

How do i bind a shared variable (array) to a Fieldpoint multi-channel item?
When i configure the shared variable, and click browse to select the network item to bind to, i can select individual channels but there's no "All" tag.

Actually I suspect that the problem is in the National Instruments OPC Server.
DataSocket can read array data types from an OPC Server, but National Instruments' OPC Servers do not publish data in an array format.
Probably the easiest solution is to publish your shared variable in your network but don’t bind it trough the opc server, instead you have to use it like a standard global variable (bind to source method).
Give a look to this document may lead you to a better solution.
http://digital.ni.com/public.nsf/websearch/FA610367EC62574186257118005089F2?OpenDocument
Hope these two tips can help you
FiloP
It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.
Richard P. Feynman

Dynamically enabling/disabling opc-binding to shared variables?

Hi.
I've got some shared variables binded to my OPC server, but sometimes some variables need to "ignore" the OPC updates and and be simulated, and in some cases, all of the variables.
So, I've got an application to dynamically change the shared variables properties: Network.UseBinding and Network.URL to "connect to" or "disconnect from" the OPC server, but is there a way to "unbind" the whole library from the OPC quickly and restore it back when need it?
I tried creating and deleting the IO server programatically but the variables go "bad"...
Is this is a good practice or should I change the method?

Hi Keptat, you can bind them directly to the OPC sever but you need to add
psp: at the begining.
For example
   psp:\\localhost\IOServer\ModbusSlave1.000001
   psp:\\aebenjamin\IOServer\OPC1.Channel_0_User_Defined.Ramp.
   psp:\\ host \ library\IOservername.register
An easy way to find the complete address y bind a Variable with psp
binding to the OPC server and you will get the path.
In the example code it gets the psp address from a Library, but won't get
you the directions of the registers inside the IOserver, so you need this list
manually.
Another option is create 2 libraries one with the variables binded to the IO
Server and the other binded to the simulated info, in this case you just have
to point to the library, and get the address of all variables.
Also you have to make sure the OPC server is deploy and you can see it
in the Distributed System Manager
Best Regards
Benjamin C
Senior Systems Engineer // CLA // CLED // CTD

About the performance of using shared variables

Hi
My system has almost 200 I/O points,I want to the host communicates with PLC using OPC(I had create a OPC I/O Server).
If I use shared variables bind to OPC data items, there must be almost 200 shared variables.
And my puzzle is that what's the performance of using these shared variables,will they eat up memory and processor?
Another question is that if an shared variable will be time-lapse(i.e.,if an OPC data item value change feedback to program block with 0 delay or not),if so ,then how many millseconds it will delaies?

here is a paper about the performance of shared variables.
Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com
Blog for (mostly LabVIEW) programmers: Tips And Tricks

Deploying cRIO as Shared Variable Engine

I am finishing up a project where a crio will be continuously recording data and the computer is running a program that will download the data once daily as well as comunicate with the program running on crio device over shared variables. Since the crio will be using a cellular modem to connect to the internet, connection loss is expected. For this reason we have made the crio serve the shared variables so that if connection is lost to the PC, the crio will continue to record data normally without problems when it writes to or reads from the shared variables.
The crio will be running headless. I built a real-time application and deployed it as startup successfully on the crio device without warnings or errors. I connected to it via font panel to confirm it started up and is working properly. I will eventually use the application builder to build an installer that will install everything needed to run the program on the PC side. However, when I open the 'Belle Glade System PC' and run it, it attempts to deploy the shared variables on the crio device. It warns me that it will close any applications running on the crio device. This is not what I want. The shared variable engine is already deployed on the crio device and the program is running. All the PC program (Belle Glade System PC) needs to do is run and connect to the shared variable engine already deployed. I am obviously doing something really fundamentally wrong here and I could use some help.
[will work for kudos]

I apologize for not posting the solution to the problem.
Basically what you end up having to do is create two nearly identical shared variable libraries, one on the pc and one on the crio. The library on the PC has each of its shared variables binded to the corrosponding variable in the cRIO Shared Variable library by PSP URL (ip address and variable location). To do this, open the PC shared variable library and go to the properties of a specific variable. Check "Enable Aliasing" and under the bind to drop down menu select PSP URL. Then hit browse and find the variable on the crio. Do this for each of the variables on the pc.
This option does not seem to be 100% reliable as it has trouble detecting connection problems between host PC and crio device. This is because shared variables look for a connection to the shared variable engine. However, both the pc and the crio have their own shared variable engine running as a host so there is always a connection as far as it knows, lol. This solution worked ok for me since I could not find a more relable option.
There is a better explaination on this post: http://forums.ni.com/t5/LabVIEW/cRIO-Shared-Variables-amp-stand-alone-application/m-p/797139?query.i...
[will work for kudos]

Shared variable among PXI consoles

I am having trouble using shared varibles via binding with two PXI-RT consoles. When I host a network variable on one PXI console and bind an object to that variable on the other PXI console, I am getting no connection. However, when I use a regular PC and bind to the shared variable, I get a valid connection...
Does anybody know why I am unable to get a connection between PXI to PXI, but it works when I do PC to PXI?
Thanks
altran

Hi Altran,
Have you ensured that the Shared Variable Engine is installed on both PXI systems? Also make sure that you don't have the shared variable binded to anything from the PXI that is hosting the variables.
Do you receive an error code when trying to connect?
Sappster

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

Network shared variables lose binding

Hello,
I am developing an application in LabVIEW that uses network shared variables to transmit data between two PC's on the same subnet. The shared variables work fine when running the VI's in development mode, however, when i build the vi's into an executable I find that they no longer work. Here is what I have found so far:
I deploy the shared variable library on the publisher machine (also happens to be the development machine) through an invoke node in the executable. NI distributed system manager confirms that this does deploy and indeed updates as it should.
For the executable on the subscriber PC I created a second shared variable library (same project) with the same shared variables and bound them to the respective shared variables from the first library by selecting enable aliasing, then bind to PSP URL and browsing to the shared variable I wish to bind it to (e.g. \\hallnet-ellm2\shared variable library\serial Number). The machines listed under browse were listed by name so when I tried this initially and it did not work I manually changed the name of my machine in the URL box to the IP address of the publisher hoping that would fix it in case the subscriber could not resolve the publishers machine alias. So now my bind URL read \\192.168.0.1\shared variable library\serial Number.
As part of the executable on the subscriber I deploy this second shared variable library. NI distributed system manager confirms that this deploys but under quality for an individual variable it has a list of issues (see attached) and the bound variable is not updating. At this point the publisher shared variables are still functioning fine. By clicking on 'edit variable' I can see that the variable on the subscriber is still bound but the PSP URL is now \\localhost\shared variable library\serial number. Changing the PSP URL on the subscriber to \\192.168.0.1\shared variable library\serial number enables the variable to update as expected.However by this time my executable has already picked up the error and does not function.
I think that the issue lies with the bind URL used on the subscriber as for some reason it does not keep the binding configured in the project and instead changes to 'localhost'. Why is this? Should it not stay bound to the address specified in the project?
I have tried changing the IP addresses in the aliases file so that
[My Computer]
My Computer=localhost
becomes
[My Computer]
My Computer=ip of local machine
This did not help.
The shared variable libraries are included in the build spec to go into the support files directory and they are successfully deployed from there on both publisher and subscriber.
I am using LabVIEW 8.6 on Windows XP
Thanks for any help you may be able to offer,
Lee
Attachments:
distributed system manager.JPG ‏74 KB

Hi Lee,
I hope you are well. Thank you for your post. Your application sounds very interesting.
Looking at your issue I was wondering, have you tried lowering your firewalls, as this may be causing the problem.
Also, another option would be to setup a private network. Do you have access to any routers that you could use to link the two machines independent of your IT's infrastructure?
The other thing to try is two other computers entirely. Again, it would be ideal to take them off the network you are on, but it's something to try if my prior suggestion doesn't work. It should work on the original two machines though, and it's likely that different computers won't solve your problems because I suspect the network.
Remember that the client variables must know the location of the variables on the server, so you can't move the server exe around without changing this value.
Make sure to set the network location in the "Bind to Source" option for the client variables.
It is also possible to write a separate piece of code to install on every machine that is responsible for deploying the library and by doing so eliminate the need for programmatically deploying the variables in the original application. However, this won't really help you, because the variables you use in the application have to be the same as the ones deployed in the library, so if you change the library, they'll no longer be linked and they won't receive data. You'd have to create a separate exe for every binding source you wanted to link to, and then have a second, known library for the sake of communication locally on the computer between the ‘deployer’ and the actual application. The main application could then be assigned the responsibility of launching the correct ‘deployer’' if it sees it needs to switch to a different variable binding source. This method is not the most streamlined or effective, but it might work.
Just to let you know, you will need to use the DSC toolkit.
Please find below some knowledge base links that I think you will find helpful in your application.
Using Shared Variables in Executables
How do I Programmatically Change the Data Binding Source for Shared Variables?
I hope this information helps and if you can give these suggestions a go and let me know how you get on, that would be great.
Kind regards,
Prashant M
Applications Engineer
NI UK & Ireland

Shared variable engine network published source issue

Hello,
I am attempting to use the shared variable engine to share some simple stings over a network between a Windows 7 computer and a Windows XP computer.
I got through the shared variable example just fine and can share variables between VIs on a single computer. When I open the shared variable engine, it shows the client and server variables that are shared on the local computer. I then create a new process, and attempt to define a new variable, and the Shared Variable Property screen comes up. I attempt to "Bind to Source" and click browse, and see the computer name I am attempting to connect to. However, when I click it, it stalls and I cannot expand the computer to find the variable I am trying to bind to. What am I missing?
Thanks, Arron

Arron,
This document may be useful in helping to setup your network shared variables. Take a look at this and see if you have followed all the outlined steps in setting up a network shared variable.
http://zone.ni.com/devzone/cda/tut/p/id/4679
Let me know how this works for you.
-Nick-
Nick C | Staff LabVIEW Platform Product Support Engineer | National Instruments

Front Panel binding of shared variables very slow initialization / start

Hello @ all,
I am using a server running Windows2000 and LV 8 DSC RTS for datalogging. All shared variables are deployed on that server.
I am now facing the problem, that all front panels running on the clients using the network shared variables on the server take very long to sync on startup. First the flags on the controls bind to the shared variables turn red, after up to ten minutes they start to turn green. The panels use up to 40 controls bind to the shared variables.
All firewalls are turned off. I tried to connect the client to the same switch the server is connected to. Same problem. Does anybody have a clue?
Thx for your quick answers.
Carsten

While I can't offer any solution to your problem, I am having a similar issue running LV8.0 and shared variables on my block diagram (no DSC installed).
When using network published shared variables, it takes anywhere from 30 sec to 4 min from the vi start for any updates to be seen. Given enough time, they will all update normally, however this 4 minute time lag is somewhat troublesome.
I have confirmed the issue to be present when running the shared variable engine on windows and RT platforms, with exactly the same results.
In my case, the worst offenders are a couple of double precision arrays (4 elements each). They will normally exhibit similar "spurty" behavior on startup, and eventually work their way up to continuous and normal update rates. Interestingly enough there are no errors generated by the shared variables on the block diagram.

Using Shared Variables and Initialize Front Panel Binding (to PSP)

Hi,
I use LV DSC RT 8.2.1
I have a Vacuum System That includes signals from - Pumps failure, Valves status, Vacuum gauge, start Pump ...
Each signal is read by a FieldPoint.
All the relevant FieldPoint Channels are read by the Server (a computer in the Ethernet Network) and published to the network in the form of Shared Variables.
I have a client VI that is reading the Shared Variables published by the Server using Front Panel Binding.
Problem :
Some of the Bindings are in the mode 'Write &Read' and that causes some initialization problems.
For example - Valve #1 is Open, and then a User start running the Client VI, (the Valve #1 Status mode is 'Write & Read")
if in the VI the status of Valve #1 is closed (before running it) then the Valve status is changing to Closed.
I want the Client VI to first read the Physical status of the instrument and then to change the Value if the User changes it.
But that's seems to be a problem when using Front Panel Binding... (is it?)
I know I can Deploy a lvlib in the Client Side and Item Bind to the Shared Variables or Use DataSocket.
(Is DataSocket is a Reliable method when connecting to Shared Variables? What are the disadvantages when using DataSocket?)
What is recommended by those of you that are experienced or by NI ?
Sincerely Yours,
Amitai Abramson.

Amitai Abramson,
Hello and thanks for using the NI Forums.
I'm glad that you've read the Using the LabVIEW Shared Variable Tutorial on our website. Check out these other resources:
Network Variable Technical Overview
Troubleshooting Network-Published Shared Variables
Why Do I See Unexpected Value Change Events for Shared Variables Using LabVIEW DSC?
All You Need to Know About Shared Variables
Creating a Value Change Event for Shared Variables
Alternative Method for Using Shared Variables Between Systems in LabVIEW 8.x
What Is The Difference Between Using Shared Variables And DataSocket VIs To Access OPC Tags?
The issue that you are seeing by having "Write & Read" bound items on both the server and client side is essentially a race condition, you don't know which one is being read/written at what time. To resolve this issue I would take a look at some of the documents below.
Using a Local, Global, or Shared Variable in Parallel Loops Can Cause Race Conditions
Using Local and Global Variables Carefully
Tutorial: Local Variable, Global Variable, and Race Conditions
Locking a Shared Resource or Variable in LabVIEW Using Semaphores
You mentioned not wanting to have two sets of shared variables (one on each side), but this is a great method to resovle this issue, that, or you can develope some sort of hand shaking to prevent these race conditions.
I would suggest that in the future when using these forums you try to ask only one question per thread and make it more concise. It's hard to tackle multiple questions and such broad questions as "I want to know all the ways that I can connect to Shared Variables, and I want to know the advantages and disadvantages." I suggest this because we want you to get your questions answered and more concise questions will result in quicker and better answers.
Message Edited by Ben S on 10-01-2009 06:05 PM
Ben Sisney
FlexRIO V&V Engineer
National Instruments

In the shared variable properties box, when enabling aliasing, what is the difference between binding to a project variable vs. to a psp url

In the shared variable properties box, specifically with regard to a the target being an rt target, when enabling aliasing, what is the difference between binding to a project variable vs. to a psp url?

The difference is in the type of variable you are binding it to. A project variable is a variable that lives within the specific project in which it was created. A PSP URL is an address using the Publish-Subscribe Protocol (PSP). You can learn more about PSP URLs here: http://zone.ni.com/reference/en-XX/help/371361G-01/lvconcepts/using_datasocket_technology/#Specifyin...
PSP URLs will enable it to communicate between different machines and also between projects which may or may not be open. The project variable will exist within the project.
Julian R.
Applications Engineer
National Instruments

Shared variable, bind to source

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