Labview 8.2 can't write shared variable

Hi!
I developed LV 8.2 program using shared variable (network published) variant type. After extension of variable the vi charased after writing value in shared variable. If i changed shared variable from network published to single proces type the vi working OK.
Attachments:
problem.jpg ‏23 KB

Hello,
I have created a network published shared variable of type variant, and successfully written to and read from it. Can you also post a snipet of your code which reproduces the problem?
General things to try in case include:
1. undeploy and redeploy the shared variable.
2. repair your LabVIEW installation - this will repair the variable engine, and I know of at least one case where this helped after it was corrupted.
I hope this helps!
Best Regards,
JLS
Best,
JLS
Sixclear

Similar Messages

Slow performance to read/write shared variables programatically

We are using datasocket read and write functions to read and write shared variables programatically (in the same machine) but we only achieve a performance of aprox. 200 reads/writes per second. We are using Labview 8.6 with DSC.
Is possible to get better results? That performance is normal?
Any help would be appreciated. Thank you in advance.

Hi MMCDAT,
I think this value can
be normal as you can see in this link:
http://zone.ni.com/devzone/cda/tut/p/id/5037
As you can see, the
limit for datasocket depends on your Ethernet limitations, even if you as using
it just in one PC:
http://digital.ni.com/public.nsf/websearch/6AC9E65734E53F9A8625672400637ECC?OpenDocument
You can improve the
performance changing the update mode or Vis configurations:
http://digital.ni.com/public.nsf/allkb/F8F7DE98856B50588625672400648045?OpenDocument
http://digital.ni.com/public.nsf/allkb/2D9C6D73A160537986256B290076456E?OpenDocument

LabVIEW 8.0 Run-Time engine & shared variables

Has LabVIEW 8.0 Run-Time Engine the shared variable's support, I wonder?
The thing is that .exe with globals/locals runs alright, but beeing replaced with shared variables it refuses to run.
What's wrong? May be need in library(s) absend?
Thanks.

You can use the Shared Variable in the Run-Time Engine (you do not need DSC).
Can you be more specific about what happens when it refuses to run? Are you seeing an error message?
If you are using Network-Published shared variables, they need to be deployed before you run the application. You can either deploy them manually with the project, or your application can programmatically deploy them. You can find some more information about this in the LabVIEW Help under "Shared Variables and Stand-Alone Applications or Shared Libraries" (follow this link and scroll down to the bottom):
http://zone.ni.com/reference/en-XX/help/371361A-01/lvconcepts/project_variables/
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Communicating Between Multiple LabVIEW Executables on different computer using Shared Variables

hi,
I need to develop some executables which will be launched on different computer of a LAN. Some DATA are common. I need to share the data using shared variables.
I usually used LabVIEW so I 'm familiar with shared variables but in this case, the RT target is a part of my
project.
I do I need to procceed in my case?
thanks

Ok but it's not my configuration and I haven't found my answer in the tutorial.
You speak of a case where there is a computer and a RT target under the same LabView project. As I said earlier, I often use labview RT and shared variable between computer and RT target. But I assume here it's different.
My question is : how do you acces to the SVE from 3 computers (without any RT target)?
1. If I create 3 labview projects using the same Shared Variable, do I need to use the same .lvlib on each project?
2. Is it possible?
3. How can I configure where the SVE should be? When I use a RT target, It only depends where I put my Lvlib. But here there is 3 projects.
James
Attachments:
Sans titre.JPG ‏9 KB

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

Can we use shared variable in main report's crosstab

Post Author: sangi
CA Forum: General
Hi,
I have a main report with subreport (in Group footer), crosstab (in Group header).
For cross tab calculation, I need a value from subreport to be passed to main report's crosstab.
I could pass the value using shared variable.. but since the crosstab is in group header , I am not able to get the values .. .it is all 0....
Please help me

Post Author: wapper
CA Forum: General
To my best knowledge, what you ask for is impossible. The subreport in group footer is going to be evaluated during the last pass, so you are too late to get values into the group header. I could suggest creating a copy of your subreport and placing it (possibly hidden) into the group header just to get the values you need... But this would be the last measure if you really can't do anything else to achieve same goal. Wapper

Can i fire Shared Variables' "Bad Status" alarm artificially?

And what shall I do to experience 'Bad Status' alarm. SVE is running on Windows platform PC.
Solved!
Go to Solution.

One shared variable one heat level sensor(DS18B20).
I want use it's "Bad Status Alarm" to alarm person on duty -
the corresponding DS18B20 sensor was failure!
But what shall I do to experience 'Bad Status' alarm first?
Don't know why, don't know the solution. Is that right?
Why there is no example project about "Bad Status Alarm"?
http://forums.ni.com/t5/LabVIEW/what-s-the-meanning-of-bad-status-in-DSC-alarm-config-for-Shared/m-p...
NI call this "answer"?

Can't connect shared variable engine

HI All,
LabVIEW 2009 + DSC
We have one test laptop on our local network. Other developers read values of some variables from that laptop. Now we have a new developer and computer. When we try to browse test laptop from network it can be found but we can't see any libraries there. This is done by using distributed system manager. PING is ok, and there is "no" firewall or virusradars. Other developers can connect that laptop well and there is no problems. Does anyone have good advices to solve this issue?
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Re-installation solved this.

Shared Variable Engine on Windows PC w/o full install of LabVIEW

I have the NI Developer Suite (8.20) and need some conformation before I get too deep in a project.
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Onto the topic of this post:
I am just scratching the surface of the shared variable interface that is available in LabVIEW 8.2. My project involves two computers where both of them need to share variables back and forth from each other. I've been reading everything I can get my hands on and I am having a hard time answering my unlying question: Is it possible for both of these machines to be running compiled LabVIEW programs and still manage the shared variables between them? That is to say, can one of the machines have the Shared Variable Engine running on it as a Windows service, or compiled into my application executable.
I've read that I can access shared variables from my compiled LabVIEW application through NI-PSP. I am wondering what my limitations would be sans-LabVIEW installation other then the troubleshooting head ache you get from developing applications without direct access to the hardware.
Thank you for your time and submissions.
-Nickerbocker

I am trying to get the "Shared Variable Client - Server" project example compiled so that both the server and client vi's can be run as executables on a standalone machine.
I have created 3 build specifications:
1. "My Server" which is the compiled EXE of the server.lvib. Added that entire library to the source.
2. "My Client" which is the compiled EXE of the client.lvib. Added that entire library to the source.
3. "My Installer" which is the installation package of the vi's and NI supporting software. In the additional installers I have added:
* NI DataSocket
* NI LabVIEW Run-Time Engine 8.2
* NI Measurement & Automation Explorer 4.1
* NI Variable Engine
* NI Variable Manager
* NI-DAQmx 8.3
Some of those are added for future needs. Installed the package on my target machine and run the server executable it appears to run fine but I get various error messages from my client.exe package (which I won't go into detail here, yet). Upon stopping the server I get the message "LabVIEW: (Hex 0x8BBB0005) Unable to locate variable in he Shared Variable Engine. Deployment of this variable may have failed."
I check the services running and see that the "National Instruments PSP Server Locator" and the "National Instruments Variable Engine" are both in the list and "Started." I open up the Variable Manager that has been installed on my target machine and manually add the "waveform" and the "command" variables under a process I call "server" and start the process. After that I start my server.exe that I have compiled from the server.lvib library. The process gives no error messages until the stop button is pressed, and then I receive the message "LabVIEW: (Hex 0x8BBB0011) The connection to the server was disconnected."
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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.

Shared variables update in QuickClient but not in Variable Manager

Greetings,
I am using LV 8.6 Developer with the DSC module installed. Also, I'm using WinXP Service Pack 3.
I am trying to create a VI that will interact with an OPC server connected to some equipment.
I've created shared variables to read the value of tags in my OPC server exactly according to the instructions on this page:
http://zone.ni.com/devzone/cda/tut/p/id/6346
For some reason though, the value of the shared value never updates to reflect the value on the server.
When I follow the tag on the OPC QuickClient, it updates just fine, but somehow the value of the shared variable isn't updating.
I also tried retreiving this data using the DataSocket method in the "Multiple OPC Items Monitor.vi" example, but running that VI crashes LabView every time.
Also, I can create a shared variable and write to tags using a VI, but I can't read them.
It seems like I'm *this* close to getting the shared variables to work. Any suggestions?

Hi Rob,
To answer your questions...
DataSocket: NI doesn't give me the option to investigate the error when I restart the program. I did a search for .cpp files, but none turned up. I did collect the error report that Windows generates, and I attached it. I'm not sure if that would be something useful or not.
SharedVariables: I went to use the Distributed System Manager to take a look at the variables. For both my shared variable as well as the tags on the I/O data source, the data type is listed as "advanced" and the quality is "unknown bad." I collected the logs from the I/O server and attached them. Oddly, when I look through there, I see some Quality=BAD and some VT_ILLEGAL flags. The deadband is set to zero, and the update rate is 1,000ms.
Also, I've configured the DCOM and Local Security Policy settings as described in numerous support articles, and my Windows Firewall is turned off. The OPC server and LabView reside on the same computer.
I suppose the confusing thing is why the QuickClient works fine, but the SVE doesn't.
I've tried this on three different computers with the same results in all cases. Currently, LV and the OPC server is the only software installed on any machine. The only other OPC server I have access to is the LV server, and it seems to work okay.
Thanks,
Wes
Attachments:
a793_appcompat.txt ‏133 KB
screen.JPG ‏105 KB
OPC I-O Server Diagnostic Information.txt ‏69 KB

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

Shared variable architecture for distributed crio system

I have a distributed system consisting of 20 cRIOs and one central server running Windows XP. Each cRIO is a mix and match of AI, AO, DO, DI and TC modules. There are around 200 AI and TC channels and close to 100 AO, DO and DI channels. I need to acquire data from all the AI & TC channels at 10 Samples/sec and log them in the Server. In some cRIOs I have 2 to 3 PID loops, in addition to the data acquisition or generation code. Since a cRIO chassis can have only eight modules, certain PID loops will have to use data of channels that are available in other cRIOs. cRIOs can be turned ON and will be running even without the control server, but facility and test will be started only through the control server.
We have decide to use LabVIEW DSC for this application and shared variable for data transfer, logging and alarm. We are using the following SV architecture.
1. Each cRIO will have its own RT shared variables for AI, AO, DI, DO and TC parameters
2. Each AI and AO parameter shared variable in RT will have its corresponding host shared variable which will be bound to the RT Shared variable. In host shared variable we are enabling logging and alarm option for variables corresponding AI parameters.
3. In cRIO RT, data is read from the FPGA (using FIFO every 500ms, and we get 5 Samples for each channel) in binary format and scaling is done. After scaling we are updating the corresponding AI RT shared variables using DataSocket write in a loop. In any cRIO there will be only a maximum of 32 AI or TC parameters.
4. The server has a mimic panel where we need to display the status of DIs and allow the user to turn ON and OFF DOs. For the we decided to use Front panel DataSocket binding.
I would like to know whether there is any better shared variable architecture that we can follow. Considering the number of variable that we are using, will the current architecture cause any performance issues?
Thanks!
"A VI inside a Class is worth hundreds in the bush"
യവന്‍ പുലിയാണു കേട്ടാ!!!

Hi Mike,
Looks like you are lucky as you can make use of the great feature available in 8.6. Over here I have 8.5.1 so got to do some of the things the 'hard' way But I must say, 8.5.1 is the so far the best version of LabVIEW I have worked after 7.1 as the crashes are less and less frequent.
BTW I faced some problems directly dragging and dropping an RT SV node to Windows. If the RT code is running and if you try to run the Windows code, it was asking to stop the code running in RT. That's one reason I had to duplicate some RT Shared variable in host and bind them to corresponding RT Shared variables.
This is the first time I am handling this many number of shared variables. In case I come across some issues, I will post them here.
"A VI inside a Class is worth hundreds in the bush"
യവന്‍ പുലിയാണു കേട്ടാ!!!

Deploying Shared Variables to Remote Target?

I have a 2-application server/client setup where my client(s) merely read information "published" by the server via a Network-Shared Shared Variable. If I run my server on a "clean machine" (i.e. no LabVIEW development) and I "publish" the shared variable library (via the "Library : Deploy Library" Application method) to the localhost, I have no problems whatsoever reading the data in the client (the path of the .lvlib file provided to the Invoke Method VI is an absolute path to the .lvlib file, BTW). However, I'm having a bear of a time getting the server to deploy the library to a machine running a second client on the same network - to do this I still use the same absolute path to my .lvlib file for the first input to the method (it's in the same place on the target as well as on the host, not that I know what this means for a targeted host) and I specify the IP Address of the target machine on the second input. There is no firewall on either machine (I removed it because I was getting nowhere and needed to eliminate a possible source of problems) and my router doesn't filter traffic going across the local subnet. Am I not using the programmatic publishing correctly to publish to another target (from within the server), or can anyone point out any problems in my usage?
By the way, if I publish to the local host (127.0.0.1 or the host machine's IP address) I do not get an error out of the "Invoke Node" VI. However, when I try to publish to a network target (both machines have the Variable Manager running and both machines work fine if both server and client are on the same machine) I get error code 1 and the message: "Invoke Node in MyServer.vi<APPEND> Method Name: <b>Library : Deploy Library</b>" which is anything but helpful.
Any help would be greatly appreciated!
-Danny

Hi Arun,
I hope you're doing well. I'd like to clarify the architecture that you are actually using. It sounds like you are deploying a network-published shared variable library on two seperate host PCs. You are then attempting to read data from both of these hosts from a RT target using the Datasocket VIs. The RT target seems to be reading from the shared variables from one of the hosts just fine, but you can't read from the other host. Are both hosts deploying their libraries in an executable as mentioned in previous posts, or is the deployment process done through the LabVIEW development system? Also, when you connect to the hosts using Datasocket, how are you entering in the addresses for each item? Lastly, it might help to know whether you have LabVIEW and LabVIEW Real-Time versions 8.0 or 8.0.1. If you could provide some more information on your set up, we can try to give some suggestions. Thanks!
Thaison V
Applications Engineer
National Instruments

Not able to access Network Shared Variable when deployed in PC

Initially, when we deploy a Network Published Shared Variable in PC and try to access the same (Read/Write) from RT, we get an error/warning "-1950679023". But when we access the same variable from the PC, it works fine. In the distributed system manager, we can see the variable getting deployed. Also the value changes in Distributed System Manager if we write a value from PC. The attached image "Shared variable Issue.png" will give more understanding of this issue.
The other way round it works fine i.e deploying in RT side and accessing from both RT and PC is working fine.
We also see that the network adapter settings is not loading properly in MAX, if at all we install any software in RT. With no software installed, it loads properly.
The following were the steps that we tried to solve the issue.
1.Flushing the entire NI software and Re- installing again
2.Formatting the RT(PXI).
3.Removing the EtherCAT Card and testing.
4.Checked the network properties of the RT network.
5.Checked the IP/Subnet/Gateway settings.
6.Checked Firewall Settings, If Shared Variable Engine is accessible.
Attachments:
Shared variable Issue.png ‏491 KB

First Root cause needs to be identified before any actions.
I would suggest first check if you can access the shared variable hosted in PC from RT using other ways like using SVE API (Logos and PS protocols, Datasocket etc..)
Check if antivirus or firewall is playing...
Check the same experiment with some other PC if you can.
You can also try creating another Shared Variable in RT and binding the same to the PC and try to access it...
Since you have did all the reinstallations already
Best Regards,
Vijay.

Labview 8.2 can't write shared variable

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