Error connecting to shared variable OPC item

I have a DSC application that has a bunch of shared variables. Some of those variables are bound to an OPC server(Eurotherm). When I place controls or indicators in a VI and bind them to the shared variable, some of them get the "green light" and some of them get the "red light". If I hover over the red light, there is a message about an error connecting to the shared variable. However, all the values update and appear to be working correctly. Why would I get this error?

Hi Brian,
Which version of the DSC Module is this? Is the OPC Server that you are trying to connect to on your local machine or on a remote machine?
Have you tried deleting the front panel object and redragging it from the project explorer? What type of value is this (boolean, double, etc?)
What are you referring to when you mean an "identical instrument" - are you connection to two different OPC I/O servers in your projects?
Would you be able to post a screenshot of this error please?
Best regards,
-Sam F, DAQ Marketing Manager
Learn about measuring temperature
Learn how to take voltage measurements
Learn how to measure current

Similar Messages

DSC VI won't connect to shared variable outside of project

My main VI will start up and connect to shared variable if I first have my project open. It will not connect to them if I try to run it by itself. I am deploying the library programmatically, but that doesn't seem to help.
Also, I can't get the main VI to run on startup.
Thanks

Hi Brian,
Thank you for the additional information. Let's put aside the run when opened issue and try to work on having your variables deploy and connect successfully.
When you run the VI within the project, are the variables successfully deployed as well?
Where are you seeing that the path to the library is blank? Where do you see that the data binding path for the variable in the working VI gets changed?
It would be quite useful for you to post a small example project, with one library, and we can tackle these questions individually, as with so many configurations (in project, not in project, running when opened, deploying successfully), I am having a little trouble keeping them straight.
Trying my best to help,
-Sam F, DAQ Marketing Manager
Learn about measuring temperature
Learn how to take voltage measurements
Learn how to measure current

Error Reading a Shared Variable Array

Hi,
I am having a problem reading an array of 20 unsigned integers from an Allen Bradley ControlLogix PLC with Labview.
I have set up a shared variable for this purpose. I have set the Data Type of the shared variable to ArrayOf Unit16. The Variable Type is Network-Published, and I have check the Bind To Source checkbox. I think my problem is in the shared variable path. I have tried the following with no success:
MyComputer\ControlLogixTags.lvlib\RsLinx\ProjectX\Online\Faults\Faults
MyComputer\ControlLogixTags.lvlib\RsLinx\ProjectX\Online\Faults\Faults[0]
MyComputer\ControlLogixTags.lvlib\RsLinx\ProjectX\Online\Faults\Faults[]
MyComputer\ControlLogixTags.lvlib\RsLinx\ProjectX\Online\Faults\
MyComputer\ControlLogixTags.lvlib\RsLinx\ProjectX\Online\Faults
I have created a simple vi for testing. I have wired the shared variable to an indicator which is an array of UInt16 items. When I run the vi, I get an error which says "Error 91 occurred at Variant to Data in Text.vi. Possbile Reason: The data type of the variant is not compatible with the data type of the input."
Does anyone have a suggestion as to what I am doing wrong?
Thanks in advance for your help,
Phil

Phil,
In order to determine that you can correctly communicate with your OPC server, I would suggest creating a shared variable bound to a single tag. It sounds as if you already have an RSLinx I/O Server in your project library. Now you can create a new shared variable and use the browse option to browse the items of your I/O server. Be sure to select a tag that has a known value such that you can verify successful communication.
Also, does your VI utilize a dynamic data conversion? The error code mentioned (error 91) is normally associated with this data type. Our next step will be to look at this VI once we can establish successful communication. I hope this was useful for you. Please let me know if I can be of further assistance.
Mike
National Instruments
Applications Engineer

I am trying to connect Dashboard shared variables to a server on a different subnet. Any ideas?

My goal is to control a device that is connected to our wired network using an Android tablet via Dashboard. I have created a vi with shared variables that controls the device as expected when it runs on a computer that is connected to the same wired network. The problem is that my Android tablet running the Dashboard app cannot connect to the shared variables on the PC running the vi on the wired network.
Our wireless network is on a separate subnet from our wired network. I am able to ping my Android tablet from the PC on the wired network but when I try to connect a variable in Dashboard, the PC running the SVE cannot be found. I tried listing it in the alternative server settings window and it still did not work. The only way I have been able to get around this is to run the vi which launches the server on a laptop that is connected to the wireless network and the wired network at the same time. My tablet can then find the server and my VI can connect to the instrument that is connected to the wired network. The laptop is somehow acting as a bridge between the subnets. I need to find a way for the Dashboard app to connect directly to the PC on the wired network. My PC IP address is 192.168.0.105. My Android IP address is 192.168.10.93.

Data Dashboard doesn't care about subnets, but it has to be able to access the server using the right ports. There is probably a firewall blocking the shared variable ports. This document explains how to configure a firewall to allow shared variables to be accessed. Your challenge will probably be to figure out where the firewall is and how to configure it.
It is also possible that the router that your Android device is connected to doesn't know how to route to the other network. Again, that is an issue with your router that you need to resolve.

CRIO and ni 9234 modules not working or communicating through fpga with accelerometers, fpga connected to real time application which is also connected to shared variables linked to modbus slave

Hi,
I have a compact rio which has a 4 way chassis attached to that chassis is three ni9234 modules they are linked using fpga to a real time application then using shared variables in the low speed loop that are linked to a modbus slave to communicate with dcs, the ni 9234's have accelerometers connected to them with iepe ac coupled option on the c modules, my problem is the real time application seems to be running okay even when power loss occurs it restarts with no problem and the fpga writes to the portable hard drive bin files fine but without a accelerometer connected I get low noise readings as soon as I connect a accelerometer to any one of the 10 outputs it just goes to a fixed number (0.03125) as soon as disconnect it again it reverts back to reading noise, I have run a scan on the modules and only get a spike when I connect or disconnect the accelerometer, I have tested the voltage at the pins of the module and I get 22 volts dc which makes it more likely that the hardware is not the problem but a software is maybe causing this to hang-up, I attach project and files for your perusal. I also carried out a new project which in scan mode directly linked the module input to shared variable and the same scenerio again. Help would be much appretiated.
Many thanks
Jason
Solved!
Go to Solution.
Attachments:
logger 2plusmodbus2.zip ‏679 KB

Whren using waveform acquisition with the 9234s we recommend the following FPGA and RT template.
http://sine.ni.com/nips/cds/view/p/lang/en/nid/209114
it can be extended as a data logger with:
http://zone.ni.com/devzone/cda/epd/p/id/6388
or using shared variables combined with scan engine
http://zone.ni.com/devzone/cda/tut/p/id/9851
The FPGA in all of these, as well as the RT framework have been used successfully by 1000s of users. I would recommend giving these a try.
Preston Johnson
Principal Sales Engineer
Condition Monitoring Systems
Vibration Analyst III - www.vibinst.org, www.mobiusinstitute.com
National Instruments
[email protected]
www.ni.com/mcm
www.ni.com/soundandvibration
www.ni.com/biganalogdata
512-683-5444

Executable won't re-connect to shared variable engine when it breifly goes offline

Hi,
I have shared variables that are hosted on a field-point controller. I read these variables from executables that run on a PC. When the shared variable engine on the field point controller goes offline and then comes back online (for instance, if I cycle the power to the controller), the executables on the PC don't automatically reconnect. I need to restart the executables in order for them to re-connect and read the shared variables.
Any ideas on how to have the executables automatically re-connect? I don't want to have to restart the execuables when the power cycles on the controller,
Thanks, Derek.

Hi Derek,
It is my understanding that the variables should reconnect, even after your FieldPoint has been power cycled. I found a few articles that could be helpful; read through these and let me know if you are still having issues.
http://digital.ni.com/public.nsf/allkb/7BA64956A475405F862570ED007B2A88?OpenDocument
http://digital.ni.com/public.nsf/allkb/04D9A85B6967EE87862571140065EEC6?OpenDocument
http://digital.ni.com/public.nsf/allkb/AA97FF29D0B3C748862572F600055B22?OpenDocument
Cheers,
Marti C
Applications Engineer
National Instruments
NI Medical

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

Error codes for shared variables in Labview 8.5?

I am trying to use Shared Variables in Labview 8.5 to enable real-time loops (similar to some of the examples in "Using the LabVIEW Shared Variable", published Aug 28, 2007). I created it to hold the result of a 16-channel A/D converter (so a 16-element I16 array). To avoid losing samples, I used buffering, with a buffer of 5. To test this, I made a pair of VIs, one a producer that stuffs a 16-element I16 array into the shared variable "every so often" (controlled by a timed loop), and a consumer loop that reads the shared variable and does something with the data.
If I think of the buffered shared variable as a Real Time FIFO (as the article suggests it is), I was curious how I would know (a) when the queue was empty, and (b) if the queue had overflowed. Both are necessary if this is to be a practical means of exchanging data -- you want the producer and consumer to run more-or-less at the same rate, but only the producer is deterministic. The consumer needs to be able to run "faster" if it falls behind (for example, because it is writing data to disk), but you don't want it to read data from the shared variable if there's nothing there. [One can always read a shared variable, after all -- as the article states, it simply "holds" the last value written to it].
Snooping around, I discovered that there are "error codes" associated with the shared variable. In particular, a code of -2220 (FFFFF754) seems to signify an empty queue (or a shared variable that has not yet been written to), while a code of -1950678981 (8BBB003B) appears to be "buffer overflow".
Is this documented anywhere? Are there other "error codes" that would be helpful to know? Is there some rationale to these seemingly-random numbers? [It would help to develop code to utilize shared variables if there was a bit less "magic" and "mystery" involved].
For what it is worth, with a buffer of size 40, I could generate 16 I16 values at 1 KHz (simulating sampling from a 16-channel A/D at 1 KHz) and pass it to a consumer node that (a) read from the shared variable until it was empty, then (b) "went to sleep" for 20 msec (simulating "doing something else non-deterministically"), and not miss any data (because I could then empty the Shared Variable RT-FIFO, which should have been half full, before it overflowed on me). Not bad throughput -- I bet I could push it even higher.
Bob Schor

Hey Bob,
The errors are documented in the LabVIEW help:
Shared Variable Error Codes
Real-Time Shared Variable Error Codes
There are several error messages for buffer underflow/overflow depending on the settings of the network or RT FIFO buffers. In particular the -2220 and -2221 are useful for the producer/consumer use case. For example (as you probably know) the consumer can flush a variable using the error code (see the attached image).
Gerardo
Attachments:
variable1.png ‏3 KB

How you connect a shared variable between internet?

Hello;
I have a aplicarían which use the shared variables, and other one which is the slave. both work rightly, in a local lan, but now I need connect the slave aplication between Internet.
what is the procedure?????
thanks in advance

Hola Joju,
La tecnología de variables compartidas sólo es válida dentro de una red local. Si necesitas acceder a una variable desde Internet, tendrías que hacer uso de DataSocket y de servidores DNS.
Servidores DNS para que tu PC tenga asociado un dominio en Internet y, de esta forma, se pueda acceder a él a través de su nombre. El problema es que tendrías que dar de alta dicho dominio. Después, seguir las instrucciones de este link, cambiando direcciones IP por nombres de equipo:
How to Use Shared Variables and DataSockets to Pass Data Between Two Networked PCs
Esto no es trivial y dependiendo de la configuración de la red del operador, es posible que haya problemas. Para comunicación a través de la red, siempre es más recomendable utilizar funciones básicas de TCP/IP o servicios web.
Un saludo,

Error with the Shared Variable Engine

Hi,
I have a problem with the Shared Variable Engine,
A .doc File is attached to this message, decribing the problem with pictures.
I will be glad if anyone can help me.
Sincerely yours
Amitai Abramson
Attachments:
Question.doc ‏819 KB

Hi Amitai,
Good afternoon and I hope your well.
A member of the team from NI Israel contacted me regarding this post.
I want to provide you with extra details on how to resolve your issue - i.e. Repair (Or Re-install) the Shared Variable Engine.
If you use the MsiBlast Tool it will populate a list of all MSI NI Installers. One of these will be NI Variable Engine. On the right-hand side you can the click 'Repair'. I would also Repair the engine support for the versions of LabVIEW you have installed. Please see attachments for MsiBlast and a screenshoot of the MSIBlast screen.
If this doesn't work I would recommend re-installing LabVIEW using the following guide, which I posted on this forum. (second post by me).
Please let me know how you get on,
Kind Regards,
James.
Message Edited by Hillman on 12-03-2008 12:19 PM
Message Edited by Hillman on 12-03-2008 12:19 PM
Kind Regards
James Hillman
Applications Engineer 2008 to 2009 National Instruments UK & Ireland
Loughborough University UK - 2006 to 2011
Remember Kudos those who help!
Attachments:
Repair Shared Variable Engine.JPG ‏97 KB
msiBlast.zip ‏110 KB

Error -1950678965 Shared Variable

I have a VI that reads a SV array. If I just plop this down on a blank vi and hit the run key it works fine with no errors. But when I put it inside of a loop it runs once then gives me this error. It doesn't matter how long of a wait I put into the loop. I've tested it as long as 5 seconds and it always errors after the 1st iteration. If I just run it manually I can hit the run button as fast as I can it does not error.
PaulG.
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind except that you happen to be insane." -- George Orwell

There is bug fix 130186 for this error

Shared Variable Engine Error Handling

I have a HMI system that connects through shared variables to an OPC Server. I have encountered problems with Variable Engine, and a problem with tagger which I don't know anything about. I checked OPC Server to see ifit's installed properly and the items status is good, and the server's connected. I tried to restart the shared variable engine service but it doesn't reply. When I monitor variables there's no connection. I used Alarm&Event query.vi in my application and then encountering tagger error, server connection failed. How could I handle these errors?
I appreciate any help.

I've created Bindings to OPC items I want to read/write through an OPC Client instance, bound front panel objects to these shared variables, deployed the entire library and run the VI.
All the connections were true (green PSP-LED. through the Monitor Variables all the variables and OPC items of client instance had good quality and right value.
All the variables were configured to log data and alarms.
Configuring the library for a data base through it's DSCsettings:database, I used Historical VIs (Read trace,… ) to retrieve data from citadel and they worked properly. I used Alarm & Event Query.vi to retrieve alarms from citadel, the VI encountered this Error:
        "Some part of tagger encountered a problem and should be closed"
After that the entire connections failed (PSP-LEDs goes red) and the I/O Engine couldn't be restarted and shows this Error:
             "Could not stop the National Instruments Variable Engine Service on local computer.
              Error 1053: the service did not respond to the start or control request in a timely fashion."
And the variable monitor dosen't show any library and variables.

Shared Variable Initial value not licenced error with cRIO

Hello Everyone,
I've a project that will be deploed on cRIO. This project was created on a different machine and didn't have any error regarding the shared variables. when I transfered the project to the computer connected to the cRIO, I have this error with all shared variable. The error message says that:
1. Initial Values: Not Licenced or can't be edited outside of LabVIEW.
2. Logging: Not Licenced or can't be edited outside of LabVIEW.
attached are two images for the error i have.
Can I have help with this issue?
Thanks in advance
Attachments:
1.png ‏134 KB
2.png ‏142 KB

Good day,
Sounds like you are using the DSC module features on your code and you forgot to activate the runtime system on that machine. If you have access to the NI License Manager, please check the status of the license.
We need an active license for the second message but, for the first one you can try to program your own initial values for all of your network-published shared variables by initializing whenever the PC is started. During the initialization portion of your code, you can just write a constant value to the shared variables so the values are the same initial values every time it is run.
Regards,
Alejandro | Academic Program Engineer | National Instruments

Shared Variables Won't Update

Hello All -
I'm having a problem interacting with my OPC server, and I'm hoping some suggestions will help me out here.
I have an OPC server running on a XP SP2 machine, and it is interacting properly with my equipment (a bioreactor). When I use the NI OPC Quick Client, I can browse to the tags I want to see, and those tags update as expected. I can put my hands on the temperature sensor and watch the output change on the QuickClient screen. The only odd thing that I have to do with the Quick Client is that I have to manually set the data type (Float, Single, Double, etc.) and request an asynchronous read before it will begin updating.
When I try to connect via Shared Variables, it's a different story. I create the shared variable using the instructions at the bottom of this page:
http://digital.ni.com/public.nsf/allkb/EA15F53DB6FECCA5862567240064DF09
Next, I drag the variable to my front panel and start the VI. A summary of the behavior is this:
* As long as the variable type is read/write, the LED is green on the VI.
* I can write values to the OPC server
* The VI never shows data arriving from the OPC server, I can only write.
* No error messages are received.
This behavior doesn't change for any permutation of "read/write" status in the variable definition, switching the node from read to write, changing the control from read to write, etc.
I'm using Labview Developer Suite 8.6 with the DCS option. Fresh install of Windows and LV. No other software on the machine.
Any ideas how to troubleshoot this? I'm running out of ideas...
One other update, which may or may not be related: Whenever I try to connect using a DataSocket method via one of the example VIs such as "Monitor Multiple OPC items.vi", LabView crashes immediately.
Message Edited by wdmarner on 10-06-2008 10:56 AM
Message Edited by wdmarner on 10-06-2008 10:57 AM

Hi Wdmarner,
When you configure OPC CLient I/O Server, what server are you using? The NIOPCServers or the Varable Engine or something else? With respect to datasockets, does the system hang or does it crash and totally exit labview?
Regards,
National Instruments
RIO Embedded Hardware PSE
CompactRIO Developers Guide

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

Error connecting to shared variable OPC item

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