Datasocket read stop but shared variable can update

Hello ,
I program with datasocket open/read, sometimes the read stops and after some time,maybe 10s, it go on reading, I compare this with shared variable (DSC) and found
the shared variable can update ,I don't know what happen to my program.
( the reason I'd like to use datasocket is that I need to change the ULR dynamically , I have many OPC tags to read ( 100 PLCs time 80 tags per PLC ) )
thanks for your help!
Solved!
Go to Solution.
Attachments:
shared variable VS datasocket.jpg ‏23 KB
shared variable VS datasocket.vi ‏17 KB

Hi~
The read function waits for items to be updated, and 10ms is the default time for this waiting. Setting wait for updated value to false will probably solve this issue.
PS: URLs of variables could be changed programmatically, see this document if you like.
Good day

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Datasocket Server vs. Shared Variables

Does anyone have any thoughts on what is better - Datasocket Server vs. Shared variables? I have a table on my application that has text indicating application status, information, warning and debug messages and would like to view it remotley over a network. The old way was to use the datasocket server and bind it to the other control. Is the new shared variable engine more efficient? These machines are at different sites.
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Hi John,
It definitely seems as if you want to gauge user experience on this issue, but since you've had no response I'll chime in and give the "National Instruments view" on the DataSocket/Shared Variable debate.
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| Michael K | Project Manager | LabVIEW R&D | National Instruments |

Shared variables not updating in exe

Hi,
I've created a project with 2 vi's, they share data via Networked Shared Variables, one vi writes while the other reads.
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Hey Gary,
I've just created a project to replicate the issue you are having and indeed when I built the application, the Shared Variables were no longer working. This is because I hadn't deployed the Shared Variables in code; which I think may be the problem that you're having at the moment. When create a Network Published Shared Variable library in LabVIEW, it auto-deploys itself for the development environment; but this is definitely not the case for when you build an executable. Instead, you must deploy the library yourself in code.
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Open up the project.
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You should see that this will give you a working Shared Variable setup. The Machine Name input for the Open Application Reference is blank because you only want to communicate with the localhost i.e. Your computer. Therefore by explicitly deploying all libraries you require, your VIs should be able to communicate effectively.
Does this solve your problem?
Alex Thomas, University of Manchester School of EEE LabVIEW Ambassador (CLAD)
Attachments:
GlobalVariableProject Folder LabVIEW 9_0SP1.zip ‏26 KB

Modbus I/O Server Shared Variable Not Updating Immediately After Flush

Hi everyone,
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Couple of points.
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This has caused me so many problems in the past (my own race conditions are bad enough without NI throwing in extra ones with this unexpected behaviour) that I try to avoid network shared variables now.
Change yours to single process and you should be fine (or do they need to be NS?)

Problems reading from bound shared variable

I have a shared variable that is bound to another shared variable. When I go to read it's value in a VI by wiring the variable to the "value" property of a digital numeric object it displays zero. When i look at the two shared variable in the variable manager they show the correct values. Does anyone have a clue what's going on?

Welcome to the forums!
Let's narrow down the possibilities here. Try wiring the shared
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National Instruments

Problema di polimorfismo con Read/Write delle Shared variable

Salve,
Cercando di modificare l'esempio di progetto "Shared Variable Client/Server" in un progetto dove sono i diversi client a mandare dati al Server ( ovvero l'esatto contrario di quello che fa )
mi sono inbattuto nel problema illustrato nelle due figure che seguono.
Ovvero, sostituendo "Writable PSP Variable" ad "Readable" nella scheda "Connect"(FIGURA 1) mi da un errore nella scheda "Read/Write" (FIGURA 2), ovviamente anche qui ho sostituito a "Read Variable" un "Write Variable".
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Qual'è la strada migliore tra Shared Variable e Data Socket per creare un sistema Client/Server così costituito, ovvero con un cospicuo numero di client da servire ( destinato a crescere )che mandano simultaneamente un discreto quantitativo di dati ( circa quelli di una seriale a 115200bps ) ad un server
FIGURA 1
IMMAGINE 2

Translation
Hi,
Trying
to modify the sample project "Shared Variable Client / Server" in a
project where different clients to send data to the server (ie the
exact opposite of what it does)
I untapped in the problem illustrated in the two figures that follow.
That
is, replacing "Writable PSP Variable" to "readable" in "Connect"
(Figure 1) gives me an error in "Read / Write" (FIGURE 2), and of
course here I replaced "Read Variable" a "Write Variable.
While using the Data Socket works, but I have clear advantages and disadvantages of using this approach.
What
is the best route between Shared Variable and Data Socket to create a
client / server system so constituted, or with a large number of
customers to serve (to grow) that simultaneously sends a fair amount of
data (approximately those of a serial to 115200bps) to a server
The images points to a gmail location. It is not properly attached.

Labview is reading zero from shared variable

Hello everyone
-I have a problem in labview shared variable cause it reads only zero value for all inputs and outputs and timers in S-1200 ...etc
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My project writes accelerometer data to usb drive but shared variables do not communicate with modbus

Hi there,
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Solved!
Go to Solution.
Attachments:
logger 2plusmodbus2.zip ‏679 KB

Hi Jasonh,
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@naga5speed ,
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Thank you again for posting and have a great day.
Please click the "Thumbs Up" on the bottom right of this post to say thank you if you appreciate the support I provide!
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D5GR
I work on behalf of HP

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
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I hope this will help for you too.
Regards,
Peter

How fast can shared variable update?

Hi,
     According to online documents shared variable engine update at 10ms or forced by flushing command. But I tested the following two program and can not get the shared variable updated:
      Thanks fo rhelp!
      Tom
Attachments:
test_program1.png ‏20 KB
test_program2.png ‏20 KB

Hi,
     I don' use NSV to transfer large amount of data between RT and host. The actual application is as follows:
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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

Datasocket and Shared Variables

I am curious if there is any advantage to using Datasocket to read/write shared variables (as opposed to a direct read/write). I'm specifically talking networked shared variables here.
Is there any speed advantage to accessing shared variables thru the Datasocket functions? Since both a direct read/write and a Datasocket PSP read/write talk to the same variable engine I assume they are equally efficient but I'm looking for confirmation here. I've seen benchmarks for shared variable performance but none of them use DS/PSP to access the variables.
Normally I would not even think of using Datasocket to access shared var's but where I currently work we have a large app that does this and it works great. I suspect that this functionality only exists in LV8.x for backward compatibility and non-Windows OS compatibility and is not really meant to be used for new, Windows-based apps? Am I off base on this?
I am working in LV 8.5, BTW.....

Hello Jared,
Thank you for the reply with clarification.
Based on your comment, I changed the buffer parameters and also tried the programs with two different data types, previously StringArray and now String.
In the attached LV8.6 project, you have all the programs, and shared variable library to review my tests.
There are two sets of two files - each set has a Write Shared Variable and Read Shared Variable file. One set is for StringArray type Shared Variable (named StrArr in the library), and the other set is for String type Shared Variable (named Str in the library).
String Array example:
MultipleDS-Write-SharedV-StrArr.vi / MultipleDS-Read-SharedV-StrArr.vi
In my String Array shared variable, I use only 4 element array, each having 4 character strings - meaning 16 bytes per String Array data. I have two loops in the write file, writing to the same variable, an array of 4 strings, each loop continues until the loop index is >0. This means, sometimes, depending on the processor speed, the variable will be written 3 times or 4 times (the variable could have a new value before the loop condition is checked).
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I am putting 2048 bytes in buffer, which is much more than sufficient in my case.
The writer loops run with 200 ms to wait for each iteration. The reader loop runs with 100 ms in DS timeout and 100 ms in wait timer. This gives results without any loss. However, if I run the reader loop with 1000 ms to wait for each iteration, the data is lost. The buffer is not maintained for 2048 bytes.
In the read program, just to make sure if all data is read or not, I am showing data in two different string indicators, showing data of each loop.
String example:
MultipleDS-Write-SharedV-Str.vi / MultipleDS-Read-SharedV-Str.vi
The String Array shared variable didn't show values in the Distributed System Manager. Hence, I created another simple variable with String datatype.
The writer program writes strings of 4 characters, one-by-one, in two loops. Meaning, total 8 strings of 4 characters each are written in the "Str" Shared variable.
The reader program, however, doesn't always display all the 8 strings. Although the wait timer is not high (slow) it still misses some data usually. Data is overwritten even before the buffer is filled (in buffer, I have defined 50 strings with 4 elements in each).
In both of the Read programs, I read using datasocket. I think thought datasocket has more ability to buffer. Earlier I had "BufferedRead" in DataSocket, which I have changed to just Read, because BufferedRead didn't give any special buffer advantage in the Shared Variable reading.
---- This is an update on the issue.
Ok, just while typing the last paragraph above, regarding datasocket, something clicked in my mind, and I changed the DataSocket functions to simple Shared variables (completely eliminating datasocket functions) in the read programs as well. And bingo, the buffer works as expected, even if I have reading loops very very slow, there is no data loss in any of the program sets.
The two changed Read programs are also included in the attached project - MultipleSV-Read-SharedV-Str.vi and MultipleSV-Read-SharedV-StrArr.vi
So this means, I can completely eliminate DataSockets (not even using PSP URLs in DataSocket Open/Read functions) from my programs.
One question here, what will be an advantage of this (or any side effects that I should be keeping in mind)?
Vaibhav
Attachments:
DataSocket.zip ‏71 KB

Read LabVIEW shared variables ( network variables?) with VB6

Hi, i need to read some LabVIEW shared variables (network variables?) using a VB6 program.
Is it possible?
I think that yes, using Measurement Studio for VB6 but I don't know how and I haven't found information in the Measurement Studio for VB6 help file
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Hello quintella,
To be able to interface with LabVIEW
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and write to shared variables in ANSI C, Visual Basic .NET or Visual C#. (http://zone.ni.com/devzone/cda/tut/p/id/4679)
Here you have two links where you can
find more information about how to use the datasocket option. In addition, there
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http://forums.ni.com/ni/board/message?board.id=230&message.id=2945&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=230&message.id=3324&requireLogin=False
Regards,

Slow update of shared variables on RT (cRIO) after building exe

Hi,
I've been struggling with this for the past few days. I am having a problem with slow updating of shared variables on my RT project....but only after building the application into exe's.
The application consists of an RT target (cRIO 9073) sampling inputs at a rate of 1sec. I have a host PC running the front panel that updates with the new acquired values from the cRIO. These values are communicated via shared variables.
Once the cRIO samples the inputs, it writes the values to the shared variables, and then flags the data as 'ready to be read' using a boolean shared variable flag. The hostPC polls this boolean shared variable and updates the indicators on the front panel accordingly.
Now, this worked fine during development, but as soon as I built the RT exe and host exe's, it stopped working properly and the shared variables ended up being updated very slowly, roughly 2-3sec update time.
To give you some more background:
I am running the Labview 2010 v10.0.
I am deploying the shared variable library on the RT device (as the system must work even without the hostPC). I have checked that its deploying using Distributed System Manager, as well as deploying it into the support directory on the cRIO and not the exe itself.
I have also disabled all firewalls and my antivirus, plus made sure that the IP's and subnets are correct and its DNS Server address is set to 0.0.0.0.
There are 25 shared variables all in all, but over half of those are config values only used once or twice at startup. Some are arrays, plus I dont have any buffering and none of them are configured as RT FIFO's either.
The available memory on the cRIO is about 15MB minimum.
What strikes me is that it works fine before building exe's and its not like the cRIO code is processor intensive, its idleing 95% of the time.

Thats exactly what I'm saying, it takes 2-3seconds to update the values.
I have tried taking out the polling on the PC side, and registered an event on the changing of that shared variable and that doesn't do anything to change the slow update time. Even if I stop the PC, and just monitor the shared variables in DSM it updates slowly.
I also tried utilising the "flush shared variables" vi to try to force the update....that does nothing.
I wire all the error nodes religously. Still no luck.
Its very strange, I'm not too sure whats happening here. These things should be able to update in 10ms.

Datasocket read stop but shared variable can update

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