I want to Host my Shared Variables on a cRIO, but use DSC for Logging/Alarming/SCADA

Hi everyone,
What I'm trying to do is this:
-Host shared variables on my RT targets (cRIO-9022) for reliability
-Use the DSC module to log to database, track Alarms, develop distributed HMI
The problem I'm running into is that the DSC engine (it seems) needs the shared variables it is monitoring to be hosted on that computer. The DSC engine can not run on a real-time target.
My end goal is to create a plant-wide network of cRIO's that are all linked back to a central server/PC that runs DSC to collect and stores data in a database. The plant HMI would also connect to the central server and get their information from there (not directly connected to the cRIO process). Is this possible/does any one have ideas on how to do this efficiently?
Thanks for the help.
--CLD--
LV 6.1, 8.6.1, 2011 SP1, 2012 SP1
Solved!
Go to Solution.

Sachsm,
Thanks for the input. I tried to create a test project for this type of architecture (bound NSV's) but am running into some errors.
I have attached a screenshot of the project and front panel showing the binding status of each variable **see attached picture**
Hosted on PC:
-Clone (Variable1) ---- This is bound to Variable1 on cRIo using the "Create Bound Variables" option in the Library
-Variable3
Hosted on cRIO
-Variable1
As you can see, when I drag variable 1 directly onto the PC front panel, the variable connects (indicator is green). Likewise, when I host Variable3 on the PC and drag it to the front panel, it connects. However, when I drag the Clone (variable bound to Variable1 on cRIO) onto the front panel, it cannot connect. Any thoughts?
--CLD--
LV 6.1, 8.6.1, 2011 SP1, 2012 SP1
Attachments:
Binding Error.jpg ‏127 KB

Similar Messages

Do I need to set host side shared variables to RT FIFO?

Hello there,
in my application a LV host application communicates with compact RIO through shared variables. On cRIO i have some shared vars with RT FIFO enabled. On host side for those vars which are bound to cRIO i did the same. Is that neccessary?
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Dear Thomas,
thank you so much for your post. The shared variable with RT FIFO enabled works the same as the RT FIFO functions on the RT functions palette. The RT FIFO is for communication between the higher priority loop and the normal priority loop. You can see it like this; if the shared variable with RT Fifo enabled is network published there is a communication loop (hidden) which publishes the shared variable to the network port of the cRIO system. The RT FIFO option is only for the communication between your high priority loop and this hidden loop. The hidden loop is executed when the higher priority loop is idle. Again I speak about hidden loop just to create a clear picture.
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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.
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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.
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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.
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Shared variables update in QuickClient but not in Variable Manager

Greetings,
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To answer your questions...
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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.
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Attachments:
a793_appcompat.txt ‏133 KB
screen.JPG ‏105 KB
OPC I-O Server Diagnostic Information.txt ‏69 KB

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Where can I find the "Shared Variable Properties" VI to be used in my program for configuring SV remotely?

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Here is a VI I re-created and posted for all. I'm not sure why NI doesn't provide their VI to the developer. The only thing I can't figure out is that when reading in the "Ack Type" into a variable, it generates an error. It will work if you go into "project explorer" and right click on the library with the shared variable and "deploy" but eventually stops working. I have tried using the "undeploy library" and "deploy library" to see if this would be a work around but had no success.
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Shared variable, missing data, the same timestamp for two consecutively data

hello
I have a problem with missing data when I read from a network published shared variable.
Host VI:
In a host VI on my Laptop (HP with WinXP Prof.) i'm writing data to the shared Variable "data". Between two consecutively write operations is a minimum of Milliseconds waiting time. I use that because I want to be sure that the timestamp for each new data value is different then the preview one (resolution shared variables is 1 ms)
Target VI:
the Target VI on a cRIO-9012 realtime device is reading only new data in the way that it compares the timestamp of a new value with the timestamp from the last value.
Problem:
rarely, I'm missing a datapoint (sometimes everything works fine for several hours, transferring thousands of data correctly before suddenly the failure happens). With some workaround I'm able to catch the missing data. I've discovered that the missing data has the exactly same timestamp then the last readed datapoint, therefore is ignored in my "legal" data.
To sum up, the missed value is written to the shared variable in the host, but the target ignores him because his timestamp is wrong, respectively the same as the last value has, despite the host waits every time for a minimum of 10 milliseconds before writing a new value.
Note:
The shared Variable is hosted on the Laptop and configured using buffering.
The example is simplified only to show the principle function, in real I use also a handshaking and I secure that there is no over- and underflow.
Simplified Example:
Question:
Has someone an idea why two consecutively data can have the same timestamp ?
Where is the (wrong) timestamp finally coming from (system?) ?
What would be a possible solution (at the moment with shared Variables) ?
-> I tried a workaround with clusters where each data gets a unique ID. It works but it is slower than comparing timestamps and I could get performance problems.
Would it change something when I host the shared Variable on the RT-System ?
Thanks for your help
Regards
Reto
Solved!
Go to Solution.

Hi Reto,
I had a look on your modified Example.
Because the Shared Variables didn`t work like Queues or Notifiers (No Event or Interrupt when a new value has been written. And for sure the´re not possible over a network) you will see the issue, that the code is reading the values more often with the same timestamp (Polling Problematic) if the reader is faster then the writer. And because the timestamp is written with the value you´re able to program like you do. Filter out whats duplicated when you have the same timestamp.
Everything is described in here:
http://zone.ni.com/devzone/cda/tut/p/id/4679#toc1
Laurent talked about a second depth of buffer. Please have also a look at the link. Somewhere in the middle of the tutorial you see the explanations of Buffer and RT-Buffer.
Regarding your question: Would it change something when I host the shared Variable on the RT-System? --> No
In my experiences, you should consider to place the Shared Variable Engine after asking some questions regarding the application.
You will find the Answers to this 3 Questions also in the link:
Does the application require datalogging and supervisory functionality?
Does the computing device have adequate processor and memory resources?
Which system is always online?
And you`re right the smalles time interval you can see in the timestamp is 1ms.!
What you also can do is working with an enabled "timed out". This might be more performance efficient than reading the timestamp.
What I don`t know and not find up to now, is if LabVIEW or the OS adds the timestamp. It´s taken from the system time, this looks like LabVIEW is taking the value and adds it.
I hope this helps
Alex
NI Switzerland

Using a Meter control in LV Touch Panel, and using shared variables that are custom controls.

I Just started using LV touch Panel module with an NI TPC-2106.
I have two differenct problems:
1) I was planning on using the "Meter" control quite a bit. I can set up the meter exactly how I like on the host PC, but on the touch Panel computer it seems to ignore my adjustments, mainly the start and end of the scale - i.e. I would like control to run from 0 to 360 with 0 straight up, using the entire circle. However, on the Touch panel computer it always puts 0 at about 7 o'clock and 360 at about 5 o'clock. I have also tried adding markers to no avail.
2) I am communicating with a compact fieldpoint controller. I can creat a shared variable that is a simple double with no problems. However, I have some shared variables that use a custom control for the variable type - bascially a cluster with a couble doubles, a time stamp, and an enumeration. It lets me drag the shared variable into my diagram, but it seems to ignore it when I run it.

Ipshita_C,
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- I have attached a simplified VI that shows how I want to use the meter. Notice that the placement of the endpoitns does not work correctly on the touch panel, and that it ignores the arbitrary markers that I placed.
- I also have included an XY graph control that displays on the TPC with margins around the graph area that I removed from the graph control.
- For the shared variable, it appears to be an issue related to the touch panel, not fieldpoint. I found another thread in this forum that mentioned that clusters containing Enumerations do not work in shared variables on the touch panel. I changed the enumeration to an integer and it now works fine.
In general, there seem to be a disappointing number of limitations in the touch panel implementation. My biggest concern is that I have not found any documentation from NI that lists these limitations. I seem to have to try things out and see what works and what does not work. Can you point me to a comprehensive list of touch panel modules limitations?
Attachments:
test 2.vi ‏10 KB

Target VI stops before being commanded using shared variable

All,
I decided to post this in general since it deals mostly with shared variables however I am working with a RT target so feel free to move it to another forum.
I originally posted a problem I was having with the RT Module Getting Started example, regarding the 1950679023 error, and trouble shooting led me to create the simplest test project I could think of. (I know you all want a link to the VIs but my company does not allow me to access internet file sharing sites to upload data so bare with me.)
NOTE: This is NOT an RT project. Just deployed on an RT target.
In Project Explorer I have Host.vi under " My Computer " and Target.VI and 3 networked-published shared variables (call them A,B,C here for simplicity) with RT-FIFO checked, under my RT target.
Host.vi is a single while loop with a 0.5sec time delay express VI. The loop contains (along w/ the time delay) 1 numeric control wired to SV A, 1 numeric indicator wired to SV B, and finally a Stop button wired to SV C plus the conditional term (stop if True). SV A is configured as write, SV B as read, and SV C as write.
Target.vi is a single while loop with a 0.5sec time delay express VI. The loop contains (along w/ the time delay) a numeric add function wired to a constant double and SV A configured as read. Also, SV C is wired to the conditional term configured as read (stop if True). The VI adds the two numbers, one of which is controlled by the Host.vi using SV A, and sends the results to Host.vi using SV B until the Stop button is pressed on Host.vi and sent back to Target.vi using SV C.
I successfully ran this project (which included my always present 1950679023 error). Then changing no code but merely redeploying/running it again right after or through out the course of many other project deployments I get incorrect data on Host.vi. Basically sometimes it would work, sometimes it wouldn't; having changed NO code. First discovery was that Target.vi would automatically stop after running ~ 1sec since deploying/running on the target and before I could disconnect and open/run Host.vi. I then deployed/ran Target.vi with a probe on the wire between SV C and the conditional term and highlight execution running. After an average of 3 runs through the loop the SV C would automatically send out a True signal even though I never open/run Host.vi. How can shared variable C, which is write controlled by Host.vi, automatically change it's state like that when I never even open/run Host.vi?
Another interesting observation is, If I first open/run Host.vi and then deploy/run Target.vi, the program ALWAYS works. But those steps go against my limit understanding of running VIs with shared variables on a target, which I got from NI's RT Module Getting Started Guide? I am going to have a hard time developing anything useful with these shared variables if I can not get the LV RT Guide example and this simple VI working. Any help would be great.
Thanks
JD
P.S. I've noticed this error message a few times during deploying/running either the Host.vi or Target.vi. The error is not consistent; sometimes I see sometimes I don;t.:
error-2147220727 (Hex 0x80040309)
The client process cannot communicate with the configuration server process. If this problem persists please note the steps you performed that led to this error and contact technical support.
PXI-1045,PXI-8196 RT,PXI-4220 (slot 2),(2) PXI-6259 (slot 3 and 4),PXI-5152 (slot 5),PXI-2585 (slot 6),PXI-5404 (slot 7)
LV 8.2.1, RT 8.2, DAQmx 8.5, MAX 4.2, VISA 4.1,
Pharlap OS ver.12.0, PH_EXEC ver. 8.2

Thanks for the responses, (sorry this is going to be long)
- First question is how do you initialize a shared variable (SV)? I don't have the DSC module, which I know has an initial value parameter. The SV is configured as a read and doesn't have any inputs, so am I missing something on the way to initialize it? I know the boolean defaults to False, which is good for my application. Also, right clicking on the SV doesn't bring up any obvious solution? Help if I am lost. Also, all my code is inside the loop (both the RT.vi and Host.vi), nothing is outside the loop.
- I think I learned something through some trial and error. I made this test VI project even simpler by just having an incremental counter using shift registers inside the RT.vi while loop. The results of that counter are sent out, by way of a network-published SV, to the Host.vi. This network-published SV is located under the target within the Project Explorer. I temporarily got rid of the boolean SV, which was used to stop both the RT.vi and Host.vi. It was that boolean SV that gave me all the problems.
This new test VI works consistently (also as a stand alone application, which was a first for me). My thoughts are that the issues had something to do with not "completely" removing all previous run instances of the VI and associated SVs/library from the RTs memory. I think I was getting old buffer data or SV corruption when, on my first test VI, would re-run the RT.vi and have the boolean SV inexplicitly switch states from False to True, even though the write controlled instance on Host.vi wasn't even running. I now undeploy everything (and check the Variable Manager) to make sure I have a clean sheet when re-running the VI. Now that brings up a question, is undeploying the only, or proper, way to clear the RT's memory?
Anywho, I reintroduced the boolean SV into this new edition of the test project (read instance on RT.vi and write instance on Host.vi, while "hosted?" under the target in the Project Explorer) and everything works (although I still get that 1950679023 error once in a while when running for the first time). Meaning, I deploy the RT.vi then disconnect, then run the Host.vi and get valid data, then I press stop and both VI's stop. I then clear out the RT memory (I think all of it?) using undeploy and then repeat. Doing this I get consistent, valid results. If this seems like a learning experience for me please let me know, I don't want something to "work" just by accident.
- To answer the second reply: 1) all the SVs where created under the target in the Project Explorer. Also, I have not unchecked auto-deploy or tried deploying manually, but will give it a try. That brings up a great point, most of NI's data on SVs is "technical specification" like and not very in depth for something so complex. I have not been able to find any "tips/tricks" or "best practices", like trying to deploy manually. Is it because SVs are still new?? Also, a frustrating thing is that NI's step by step tutorials treat SVs like they are simple and fool proof, but following their instructions to the T I get errors. They leave out all the little nuances of correctly working with SVs and so it creates a steeper learning curve. Enough of my rant.
Thanks again for the responses and any more help to come.
JD
PXI-1045,PXI-8196 RT,PXI-4220 (slot 2),(2) PXI-6259 (slot 3 and 4),PXI-5152 (slot 5),PXI-2585 (slot 6),PXI-5404 (slot 7)
LV 8.2.1, RT 8.2, DAQmx 8.5, MAX 4.2, VISA 4.1,
Pharlap OS ver.12.0, PH_EXEC ver. 8.2

What is the best way to create shared variable for multiple PXI(Real-Time) to GUI PC?

What is the best way to create shared variable for multiple Real time (PXI) to GUI PC? I have 16 Nos of PXI system in network and 1 nos of GUI PC. I want to send command to all the PXI system with using single variable from GUI PC(Like Start Data acquisition, Stop data Acquisition) and I also want data from each PXI system to GUI PC display purpose. Can anybody suggest me best performance system configuration. Where to create variable?(Host PC or at individual PXI system).

Dear Ravens,
I want to control real-time application from host(Command from GUI PC to PXI).Host PC should have access to all 16 sets PXI's variable. During communication failure with PXI, Host will stop data display for particular station.
Ravens Fan wrote:
Either. For the best performance, you need to determine what that means. Is it more important for each PXI machine to have access to the shared variable, or for the host PC to have access to all 16 sets of variables? If you have slowdown or issue with the network communication, what kinds of problems would it cause for each machine?
You want to located the shared variable library on whatever machine is more critical. That is probably each PXI machine, but only you know your application.
Ravens Fan wrote:
Either. For the best performance, you need to determine what that means. Is it more important for each PXI machine to have access to the shared variable, or for the host PC to have access to all 16 sets of variables? If you have slowdown or issue with the network communication, what kinds of problems would it cause for each machine?
You want to located the shared variable library on whatever machine is more critical. That is probably each PXI machine, but only you know your application.

Deploying cRIO as Shared Variable Engine

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

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

Shared Variable communication (network publiched )

Hi all ,
The whole day I have been banging my head with Shared variable communication between RT Host and host computer :
I essentially attempted to pass an array from the RT host to the Host computer .For this purpose I used a Network published shared variable of type Array U64 . I utilized this link to help me understand usign shared variable communication
http://www.ni.com/white-paper/4679/en ..
I also enabled RT FIFO .Now in the mentioned link this the information given about using single element FIFO or Multi element FIFO
'' By enabling the real-time FIFO, you can select between two slightly different types of FIFO-enabled variables: the single-element and the multielement buffer. One distinction between these two types of buffers is that the single-element FIFO does not report warnings on overflow or underflow conditions. A second distinction is the value that LabVIEW returns when multiple readers read an empty buffer. Multiple readers of the single-element FIFO receive the same value, and the single-element FIFO returns the same value until a writer writes to that variable again. Multiple readers of an empty multielement FIFO each get the last value that they read from the buffer or the default value for the data type of the variable if they have not read from the variable before.''
I had read the above content a 100 times but still I am not able to get a clear picture of the difference and when to use which option .So I decided to throw away the text and attempted to try somethign out for myself .
I had a loop in the RT host that writes different 3 element arrays into the ''network published shared variable '' . Now when I use the multi element option with '' number of arrays as - 2 '' I am able to read the arrays seperates one by one in the host computer ( as we can read a general queue).
Now when I used the single element option for the RT FIFO with un editable 1 array option ,only the last written array into the ''network published shared variable '' gets read in the host computer .
This sounds absolutely silly as if this is the case then what is the purpose of setting the ''buffer''.For testing purposes I had set the buffer as 5 arrays .
In fact I have only one writer ( writing in loop in the RT Host ) and one reader ( again reading in loop in the Host computer ).So I am not even sure if I require The RT FIFO option for the network published shared variable .
I apologise for the long message but I have reached the limits of running in circles waiting to bang somewhere
I know I am doing a silly mistake somewher or I am probably missing a simple obvious trick but dont know what it is ..
I request for some clarity .. In fact I had posted a little while earlier today as well .... link - http://forums.ni.com/t5/LabVIEW/RT-Host-to-Host-computer-communication/td-p/2348130 )
any help would be appreciated
Cheers
me
Solved!
Go to Solution.

Hi,
I think the difference between both types is clearer in the LabVIEW help :
Enabling the Real-Time FIFO
You can enable the real-time FIFO of a shared variable from the Real-Time FIFO page of the Shared Variable Properties dialog box. Place a checkmark in the Enable Real-Time FIFO checkbox to deterministically share data using single element or multi-element FIFOs.
Single Element FIFO
A single-element FIFO shares the most recent data value. The shared variable overwrites the data value when it receives a new data value. Use this option when you need only the most recent value. Configure the size of the array elements or the size of the waveform for the FIFO buffer if you select an array or waveform data type.
Multi-Element FIFO
A multi-element FIFO buffers the values shared by the shared variable. You can configure the size and the elements of the FIFO buffer to match the settings from the Use Buffering section of the Variable page, or you can configure a custom size for the FIFO and the FIFO elements.
Note For both single-element and multi-element FIFOs, if the variable contains array or waveform data, you must configure the size of the FIFO elements equal to the size of the data you want to share. If both the network buffer and the RT FIFO are enabled, the network buffer must be at least as large as one FIFO element. Sharing data smaller or larger than the length you specify causes a memory allocation that affects determinism.
Note Waveforms contain variable-size variant elements that are not compatible with the Real-Time FIFO. Therefore, if you enable the Real-Time FIFO on a shared variable that contains waveform data, the variant element of the waveform data does not transfer.
http://zone.ni.com/reference/en-XX/help/370622K-01/lvrtconcepts/rt_projectvariable/#Single_Element_F...
'Hope it helps
Aurelie

I want to Host my Shared Variables on a cRIO, but use DSC for Logging/Alarming/SCADA

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