Read shared variable using D/3 DCS

This is a rather odd question.. I think it can be done, but I have not yet figured how.
A client has a DCS System (I believe from NovaTech), which communicates with a database.
They use a different PC to get data from a cFP using Shared Variables.
There is mention of data being sent over a Modbus Interface.
They want to know if it is possible to read the Shared Variables directly using their DCS System. If the DCS was from NI, it would probably be easier to accomplish. However, I am not at all acquainted with the NovaTech product, but I believe there must be a way to innterface to it. Probably using Data Sockets and/or PSP Protocol.
I realize the above is rather obscure... I have sent an email requesting more info and I am preparing the next email. I figured that I'd better do some background investigation and ask proper questions.
Has anyone attempted such a thing or similar? How about reading Shared Variables from Non-NI software? I did find some threads discussing reading/Writing (to/from) Shared Variables using LabWindows-CVI, but I suspect this will be quite different. Maybe I'm wrong..

Thanks Christian.
I will continue in this thread after I find out more details from the client.
RayR

Similar Messages

How to read shared variables inside event structure ?

Hi,
I have a problem that my shared variables do not update inside event structure. The program(s) I am trying to get working is seen in the attached screenshot. It works as follows:
0. I start the vi that is unsquared.
1. I write a string to a shared variable using vi in red square. I make sure that its updated using write-wait-read.
2. I run the other vi (blue square), this changes the boolean shared variable.
The unsquared vi has been running the whole time, it has event structure bind to boolean shared variable change (the one in blue vi). After I have runned the blue vi, the unsquared vi should change the indicator values to match the ones in red vi. However I have to start the blue vi multiple times to get it to change, sometimes even 6 times.
Also, when I change the value in red vi to a third value and start blue vi multiple times, the unsquared vi shows all the variables. I.e. I put "cat" to red then start red, put "mouse" to red then start red,... and then start clicking blue... Unsqured shows cat, mouse,..., dog (dog is the default).
How can I force the shared variable to update inside event sructure. I want the current value of the variable, not some historical values.
Attachments:
Screenshot-5.png ‏108 KB

Found the buffering... disabling it solved the problem... thanks.
FYI, there is another solution that I just found out... attached. Adding timeout to the event structure and the variable read outside the event structure... This makes the shared variable strings (one that is read outside and the otherone that is read inside) different.
Could someone explain why the variables are in different state even if they are used in the same place and looped with 10ms intervals?
Juha
Attachments:
Screenshot-6.png ‏110 KB

Weird delay reading shared variables

Hello,
I'm working on a project were I'm monitoring some prodution lines. I'm using DSC module's OPC server to connect to PLCs on the production line and I've created bound variables on my labview project of the PLC's tags.
On my project I have one main VI were I show information about the production lines and were I can access several subVIs were I show other information about those lines. Then I have a VI that is running in background were I'm reading about 50 shared variables from the PLC and where I'm registering some data in a MySQL database, datalogging data on the Citadel database and registering alarms.
The problem I'm having is that on the VI that runs in background I noticed a delay reading the variables that are reading containers weights from the production line. It seems that all the other shared variables don't suffer any delay, only the weight variables start having some delay when the values are increasing. It also seems like that, when I'm only running that VI alone, without running the main VI, there isn't any kind of delay. I'm reading the shared variables as shared variable nodes.
Can anybody help me understand what's happening and how can I fix this delay? The VI that runs in background is time critical and a weird delay like that messes up my data.
Solved!
Go to Solution.

Hi Mateus23,
The shared variable has various buffering capabilites, including integration with the Real-Time FIFO feature in LabVIEW Real-Time.
I guess that the buffering settings are causing the unexpected behavior.
Check these resources:
Buffered Network-Published Shared Variables (whitepaper)
Shared Variables Properties Dialog
- Network Page
- Real-Time FIFO Page
~~

Unable to read shared variable in signal express

Dear all,
I am trying to read a shared variable with data type 'Array of Double Waveform' and the signal express gives a network variable error stating
"The data type of specified shared variable xxxxxx is not supported".
could any one explain why is this not supported or suggest a work around.
Munir.
Attachments:
Untitled-1.jpg ‏66 KB

Hi Munir,
the datatype you want to use is not supported in Signal Express. So if you choose this datatype you always get this error massage. As a work around I can recomment you to take the Double Waveform datatype this is supported, create a shared variable for each array element (waveform) and read this variable in Signal Express. This should help you out.
If you got any questions feel free to ask me.
Regards
TomBaum

Can not read shared variable on cRIO, error -1950678968 nitaglv

Hardware setup:
Laptop
Laptop connected via USB to a frammer garber.
Laptop IP: 192.168.0.2
NI vision calculating a diameter and setting a network varaible
cRIO
cRIO connected to the laptop
cRIO IP: 192.168.0.1
Project has the shared variable in the cRIO library
NI vision writes to the variable on the cRIO. I can see the variable properly updating in system manager on the cRIO. I can also run a VI in my computer that shows the variable properly updating. But...... When I read the variable with a VI running on the cRIO, I get the folowing error and the variable never updates:
Error -1950678968 occurred at Shared Variable in Main.vi
Possible reason(s):
LabVIEW: Failed to load nitaglv, which is required for Network-Published Shared Variables.
This error or warning occurred while reading the following Shared Variable:
\\NI-cRIO-OASIS\cRIOVariableLib\BubbleDiameterFromVision
\\192.168.0.1\cRIOVariableLib\BubbleDiameterFromVision
(I do not get any errors at deloyment)
So everything (NI Vision, a VI deployed on the laptop, NI Distributed System Manager) can see the variable on the cRIO being updated by the NI Vision.... Except for a VI running on the cRIO.
I have verified that I have Network Variable Engine and Variable Client Support for RT installed on the cRIO. I have tried reinstalling all s/w on the cRIO. Tried rebooting all. And talked in a nice, positive, reassuring voice to the chassis.

Hi!
I just had the same issue with my cRIO 9073 using NI RIO 3.6.0.
The problem is not caused by a corrupted project, but the improper installation of the OS on the target. There is nothing you can do using the SW installation wizard in MAX, as it does not matter if you intall a full RIO SW, minimal or custom.
You have to install the full install or a custom one with Shared Variable support. Then you have to FTP to the cRIO, and manually edit the "ni-rt.ini" file located in the root of the controller.
Make sure you have a line in the "[MODULE VERSIONS]" section which shows the version of the nitaglv.out file. (The problem is caused because this dll is not loaded when you try to access a SV) Mine looks like nitaglv.out=6.3
Then you have to insert "nitaglv.out;" without quotes to the [LVRT] section's StartupDLLs key's value. I did it after the taggerrt.out name. So my key entry now looks like this:
[LVRT]
StartupDLLs=nisysapirpc.out;NiViSrvr.out;NiRioRpc.out;taggerrt.out;nitaglv.out;sysstatepublisher.out;
memoryChecking=False
LABVIEWRTDir=/c/ni-rt/system
PATH=/c/ni-rt/system/;/c/ni-rt/;
CDIntervalTicks=55
WebServer.Enabled=FALSE
RTTarget.VIPath=/c/ni-rt/startup
RTTarget.IPAccess=+*
RTEnetRcvMode=2
RTCPULoadMonitoringEnabled=True
RTTarget.ApplicationPath=/c/ni-rt/startup/startup.rtexe
server.tcp.access="+*"
RTTarget.LaunchAppAtBoot=True
RTTarget.EnableFileSharing=True
server.tcp.serviceName="Main Application Instance/VI Server"
After you are done with the editing, you have to save the file, and overwrite the original one. You have to reboot the controller for the modification to take effect.
After this you will be able to host your variables on the cRIO and also read/write them from the application running on that same target.
I hope this will help for you too.
Regards,
Peter

Shared Variables using Two Computers and Crossover Cable

I'm just trying to put together a simple bench test tying two computers together by a crossover cable. They ping correctly to each other. I used the LabVIEW examples for TCP connections and they talk correctly that way too. I try to build and deploy shared variables on one computer, but the other computer will not identify the SV's on the first computer and vice versa.
Can someone give me some details on how to build, deploy, and effectively use SV's? I've read all the NI documentation, but I'm not getting the step-by-step approach very well.
Thanks.
Nathan - Certified LabVIEW Developer
Solved!
Go to Solution.

Are you making them network published shared variables and binding them to each other? This doc gives a pretty good step by step:
http://digital.ni.com/public.nsf/allkb/7815BCE435DCC432862575DA006FEBF8
--Ryan

Reading shared variables

hi ,
im having problems reading a shared variable value from a vi ,
i created a project library , periodic i/o server deployed it. created the shared variables i needed . bound them , created my new vi draged the shared variable i wanted to read , just a time value , set it to a indicator , then ran the two vi s the triangle has apeared on both the main vi and the hmi vi ,and is green , no conflicts arose , but the hmi vi isnt displaying the data ,
both vi s are on the same computer , have i missed somthing ,?

Hi Vadajooz,
Good Morning and I hope your well today.
I was wondering how you got on with your application and if you still require support?
If so, I would be interested to know what version of LabVIEW you are using?
I would make two simple VIs, one to write to the variable and one to read from the variable.
1. Create the bound variable.
2. Deploy the library, make sure it appears in the Distributed System Manager (DSM - LabVIEW 8.6+) or Variable Manager (LabVIEW 8.5 - ).
3. Run the writer VI, for example, just have a switch (true/false) and when you change the switch state does the status update in the DSM or Variable Manager?
4. If so, then run the reader VI, is the status matching the writer and there DSM/Variable Manager.
*DSM/Variable Manager can be found by going to tools>>... in the VI toolbar.
If you are still having problems,
A. There is a known issue with bound variables in LabVIEW 8.6 - so I can inform you on this if you are using it.
B. I would confirm that the variable is deployed - to do this right-click the library and select Deploy All.
C. Make sure you write to the variable before reading from it.
D. Add error cluster indicators and note any errors you see.
E. Please attach your simple (test) project - so we can confirm its correct.
I hope this helps,
Kind Regards
James Hillman
Applications Engineer 2008 to 2009 National Instruments UK & Ireland
Loughborough University UK - 2006 to 2011
Remember Kudos those who help!

Reading shared variables in C.

Hello all,
How would I recognize the value of a LabVIEW shared variable within the C programming of an mbed microcontroller (LPC1768). We have created a connection between the mbed and LabVIEW, but can't tell if the shared variable we created is actually being passed to the mbed.
Thanks,
Joe Maness

If you extend your LabVIEW by the Measurement Studio option you'll get a licenced .net component called NetworkVariables, which allows to access the shared variables engines processes and it's variables.
I don't no the IDE / Compiler you use to program your controller, but if it's able to handle .net / COM you have all options to access the SVE and there's no need to involve LabVIEW.
Feel free to ask more
Christian

Shared Variable used for Subreport Record Selection

I have a couple of shared variables created in the main report. But I get an error message "Shared Variable can only be used WhilePrintingRecords" when I try to incorporate them into the subreport's record selection formula. Any suggestions?
Thanks,
Art

the report to capture the values should use
whilepritingrecords;
shared nubmervar x:= x + field;
the one to display (your sub shared variables)
whileprintingrecords;
shared numbervar x;
x

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

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

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

Is Shared Variable Engine with LV8 an OPC server ?

Hello
Is the shared variable engine with LV8 an OPC server ?
Does any OPC client can acces to Variable Engine OPC server an read shared variable ?
Can I build an installer and deploy my application with Variable Engine OPC server on other PC without LV8.
Thank you

Hi
You can communicate between an OPC serveur and LV8 and use shared variable. To deploy an LV8 exe application, you must have the run time engine installed on the PC without installing LV8. You can create a setup with LV 8 in which you can integrate the run time engine.
Kamal
NIF

Shared Variable Engine

Hi,
What happens to network variables stored in the RT machine after a restart(after calling RT restart). I am experiancing weid behaviour.
They seem to reset to a default value and I checked in the project via their propertis, Initial values is not set, and there are no callers at the start of the VI.
Anyone has any ideas for this? Or at least tell me if values should persist after restart or reset?
Thank you very much,
Mihai

Hi,
I use shared variables stored on a PXI RT embedded controller.
After a reboot, the variables are not set to the default value corresponding to their data type structure but to a "no known value" state (I don't know how it's exactly labelled in english, as I use a french version of LabVIEW).
I noticed that if you try to read a shared variable in a "no known value" state using the "read variable" VI, you just get a warning. If you use the "read variable with timeout" VI, the code waits for a modified value of the variable, but once the shared variable has been initialized (ie has a known value) no stop occurs at the first reading with the "read variable with timeout" VI (even with an infinite timeout), as the current value of the variable when the code is launched is viewed as a "new" value.
Not sure that this message will help you
I've also experienced strange behaviours in reading shared variables : I've posted here a message in the french section af the forum, but without answer ; I plan to repost it here after new tests.
Best regards,
HL

Shared Variable Crashing LabVIEW

This is just one of those projects that has a brick wall at every turn so far. Two computers running LV2009. Computer A hosts Data Write Shared Variable. Computer B hosts Data Read Shared Variable. Data Read is bound to Data Write. Everything was working fine, and then late yesterday afternoon, I don't think I had changed anything on the shared variable, I start up my VI on Computer B, and LV crashes. The VI starts to run until the first execution of Data Read, and then poof, everything open in LV dissapears. The problem is one hundred percent repeatable since then.
Here is what I know:
1. An error indicator hooked to Data Read shows -1950679034 (Shared Variable has no value) for about a second before the crash. Everything stops executing as soon as the warning appears.
2. The Data Write is single writer, but it is also occasionally read in the VI that it is written in. It is not being read when the crash happens. I can however perform the read on Computer A without incident.
3. Not sure if this is related, but if I open the VI on Computer B, and then open the project, I am not able to drag Data Read from the project onto the block diagram. I also cannot perfrom any operations on the Shared Variable (like right click, ignore timestamp). I have to close the VI and reopen it from the project. Thinking back, this problem may have started when I opened the VI without opening the project.
I am torn between abandoning Shared Variables and trying to figure this out. I would definetely prefer to use the Shared Variable, especially because I need some buffering. I'm guessing I can buffer things some other way. Not sure if I can remotely access a queue, or ... ?
Solved!
Go to Solution.

I looked at STM, but I think the Data Socket VI's may be a better fit for me. It seems like Data Socket and shared variables are sort of intertwined, but I'm hoping DS doesn't suck as much as the SV seems to so far.
I think NIC means network interface card? Anyway, I don't really know how many I have. The Data Writer is on a PXI8108 with Windows, the reader is an old crappy Dell that I inherited with the desk.
I'm also not sure about the logos.ini file you referred to.
My intention is to transmit an array of double waveform that is about 15 - 20 channels acquired at 100 - 1000 Hz. I think the Data Socket looks like the simplest way to do this, and I could live with 100 Hz if speed is a problem, but I sort of don't think it will be. I'll try tomorrow unless somebody has a better suggestion.
By the way, I saw in another post a similar problem with Shared Variables that is supposedly fixed with the new patch for 2009, but I'm not sure I trust SV's because this will, for about thirty seconds of its lifetime, be one of the most critcal applications I've written, so I want confidence that it will work for those thirty seconds.

Read shared variable using D/3 DCS

Similar Messages

Maybe you are looking for