Does a network published shared variable drop the waveform attributes?

I have the analog input source for a waveform on one NI chassis. The trigger to begin the trend is on another NI chassis. Both of them feed data to a remote Windoze host. I would like to know how I can pass the waveform attributes, ie. Plot Names from the source machine to the Windoze host using a network published shared variable. I am using LV8.0. My two remote chassis are both running RTOS.
I can see that when I set up the DAQ assistant and named my aquired signals, that these names are passed to a waveform chart on the same block diagram. I can use them to update the Plot Names on my front panel. However, when I create an "Array of Double Waveform based" network published shared variable, and then read that variable from the Windoze host there are no attributes attached. The waveform shows up just fine.
I would like to be able to have the attributes update the plot name when I change the plot. I will have about 20 plots and I only want to display them a few at a time. I also want the user to be able to select which one they want to look at.

Hello,
I think you posted the same question to another thread, received an answer, and have now moved on. Anyway, the workaround to the problem is to peform flatten to string and unflatten from string operations on the waveform before and after sending it to the shared variable respectively. See the attached screenshot for the specifics.
I hope this helps!
Best Regards,
JLS
Best,
JLS
Sixclear
Attachments:
Workaround Screenshots.JPG ‏206 KB

Similar Messages

Network-Published Shared variable access

How can I deny the writing access to a network-published shared variable from all the network machines, except the machine where the vaiable was deploied??

Hi Idilio,
Which version of LabVIEW do you use? Do you use DSC? Where precisely do you specify your security options?
Cordially,
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Mathieu R.
  CTD - Certified TestStand Developer / Développeur TestStand Certifié
  CLAD - Certified LabVIEW Associate Developer

Programatic Access to network published shared variable - Knowlege Nugget

Wanted to Share a coding problem I have just resolved:
I have been trying to debug the code above.
It worked for one device and not the other (Identical devices: DevA,DevB)
It has been throwing an error, unable to access variable.
I resolved the problem by changing by changing the timeout to something > zero
Hope this helps future travellers
This seems onlt yo be a problem during the first connection to the variable,
Subsequent reads don't seem to need it.
It is almost as though it needs time to troll through the project shared variable database to finde the reference the first time through.
iTm - Senior Systems Engineer
uses: LABVIEW 2012 SP1 x86 on Windows 7 x64. cFP, cRIO, PXI-RT

Ben wrote:
Since I don't use shared varibales I have to ask...
Is there a timestamp returned that reveals the state of the variable?
Ben
The timestamp is only available on the reads. It returns the timestamp of when the variable was written to.
One more thing to watch out for (we recently got bit by this). The NPSV is actually written to a buffer (8kB?). The variable is published either when the buffer is filled or 10ms has passed. There is a command to flush the buffer to avoid this 10ms delay.
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Problems writing to network published shared variable hosted on rt (set as modbus slave for crio)

Hello Ni Forums
This is my first post on this forum and I have been using labview for about 8 months now
I have a problem regarding writing data to modbus registers through an i/o server set as a modbus slave for my 9074 hardware.After I have completed building project and deploying the variables and following instructions from here , it yields no result but a line zeros. I have the Ni DSM open and modbus master setup to see whether the data is actually being read/written from the respective sides which both yield the same line of zeros as well. What I am actually trying to write to is an array of single precision floating data. The registers are structured from ranges F40000-F46534 for 10 elements or have them for range AF40001L1-AF46534L1 of item AF40001L10 where it is an array of length 10. (Referenced ranges here)
I know 1 thing for sure, the modbus connection works and is ready for data requests, I tested this through NI DSM and manually set data for and my master received them .
System and Project specifications
Windows 7 OS
Labview Full Development System 2011
No Labview DSC module but I am using the real time module as referenced by one of the documents
This project is a real time application with fpga mode (not scan interface mode)
The master and slave are the same subnet and network
Modbus Connection Type: TCP
9074 compact rio 8 slots
9234 module x3
9221 module x1
9472 module x1
Shared Variable Engine service running on windows os and rtos system
Used this guide to learn about the modbus protocol as I searched all over the internet to learn about modbus
I already having Modbus IO Server software installed on the crio through ni max version 1.8 for NI RIO 4.0
attached file(s)
Image of Crio software specifications
Image of the Data being written into variable in rt block diagram
Short Version of the problem: Why is the io variable not being written into with properly converted data?

The data can have zeros but not all of them will be zeros and I have another program (on local computer for database storage)that is recieving the same data through TCP and they are not zeros.
If a machine is running and is active then the data that will be collected should not be zero , it should infact be some analog value > 0.
I will look into the function you described
How do you view the errors in the IO server subfolders ?
Is it the modbus register called error status that returns an error code if so that value is currently 0
Regards mzamstl

Test network published shared variable

Hi,
I want to share data from a main VI to other VI´s on network (different PC´s) however i want to test it using a single PC. Is possible to make that test using a main VI and trying to share variables "on network" to receiver VI...?

Absolutely!
When in doubt, try it out.
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Problems with communication across a network using shared variables

I have two programs(projects) running on two different computers connected with a LAN. I am using LabVIEW 8.0, and the DSC-module. The program on one of the computers have measurements that I want to collect and show on the program running on the other computer on the network. I choose the indicator where I want to show the data, select ''Properties'', ''Data binding'', ''Shared Variable Engine (NI-PSP)'', ''Network Items'' and then browse for a Network...but the problem is that in my ''Network Neighborhood'' There is only one computer...and that is the one I am one...not the computer on my Network that I want to communicate with....
Have anyone any suggestions on how to solve this?
Kind regards Mari

Mari,
Check this link regarding trouble shooting network-published shared variables:
http://digital.ni.com/public.nsf/websearch/6E37AC5435E44F9F862570D2005FEF25?OpenDocument
This might be a firewall issue, so I would check that first.
Frode

Can I use the timestamp of a Network published global variable to reduce network traffic?

I would like to use a couple of network-published global variables that will contain large clusters of data. I want to host them on one device but read them from several - consider a distributed control system. The data will update very infrequently, but, when it does, I want all my HMIs to know quickly. I can have all the HMIs just read the data 4x/second (that would be fast enough) but I was wondering if there is a more elegant solution (still using global variables). If I read only the timestamp 4x/second from each of the HMIs, compare it to the last read, and then poll the whole variable only if the timestamps are different, will that require less resources than just grabbing the whole variable every time? In other words, does reading the timestamp use the same amount of resources as reading the whole variable?
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Solved!
Go to Solution.

mark3545 wrote:
So that means they are already doing what I want anyway, right? If the reader only gets updated when the writer changes it, I can poll it as often as I want without increasing traffic, correct?
That is correct.
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Shared Variable through the internet

We have a remote site that is running LabView to record some data. Currently we can log on to the computer using VNC (remote control software), we use a static IP address with a port number that connects to a gateway that uses port forwarding to get to the machine of our choice. Doing that we have control of the whole computer, but the transfer of anything is slow and the screen refreshes about every 5 seconds or so using a low (64) color setting, using full color is almost painful.
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Bryan,
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Using network shared variables in two computers connected via a network switch

let me start by saying im a rookie to the programming environment but i have used Labview a couple of times to understand the basics, i have a computer and a laptop (both using vista), both of them with Labview Full development System (Student ed. with Mathscript) installed, so what im tryin to do is to use the built in microphone located in the laptop to aquire sound and then use a Shared Variable to transfere the sound signal from the laptop to the computer, the laptop and the computer are connected to a network via a network switch and ethernet cables, so far i nothing worked, i can manage to create the shared variable in the laptop and use it there but it doesnt appear in the computer, im not sure whats the problem i have even disabled firewalls in both systems, help from anyone wil be appreciated.....

Hi Lukie,
This KB should be of some assistance to you.
Trouble shooting network published shared variables
Also the following link gives some instructions on the use of shared variables.
http://zone.ni.com/reference/en-XX/help/371361B-01/lvhowto/bind_to_source/
I hope this is of some assistance, let me know if you have any more problems.
All the best,
Message Edited by mickeyw on 08-05-2008 12:29 PM
Mike W
Applications Engineer
National Instruments UK&Ireland

Custom data type causing trouble in deploying shared variable to RT target

I seem to be having some difficulty in using a network published shared variable created from a custom data type when deployed as an executable on an RT cRIO target. I'll start by describing why I believe this is where the problem lies. I created my RT VI in the LabVIEW development environment (LV 2012) and everything works fine. This VI is pretty simple because it rapidly devolved in to a debug exercise. The RT VI starts by simply blinking the User LED a couple of times and then starts a simple acquisition loop to read a few values off the hardware using the scan engine (while still blinking the User LED). After reading the hardware, the values are bundled in to a cluster and written to a network-published shared variable defined by a type def custom control. The custom control contains five dbl precision floats. If it matters, the cRIO RT system hosts the shared variable in this case.
So, I deploy this under the development environment and everything works fine. The LED blinks merrily along, telling me that the program is running properly. Running a host VI that reads the network-published shared variable yields the desired result. All is good.
Now I want the cRIO system to run this simple program autonomously at startup. I build it, set it as the startup VI, deploy it and then restart the cRIO target. The LED never starts blinking... the VI does not seem to run. I will spare you most of the debugging work and jump to the end. I basically "Diagram Disabled" various sections of code until the VI started running correctly as an executable. I kept reducing the size of the disabled code until only one thing was disabled: the write to the custom data type shared variable.
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Thanks in advance for your help!!
Solved!
Go to Solution.

Paolo,
So I thought that you meant to disconnect them in the build specification. Under the Additional Exclusions in the build specification, there is a check box for Disconnect Type Defs. I checked that box, recompiled, redeployed and it did not work. At this point I had to give and move forward, so I was going to convert the data typed from a cluster to an array. When I went in to change the data type in the shared variable pop-up from the project explorer, there was a big button under the variable definition that "Disconnect from Type Def". Clicked that button, recompiled, redeployed, restarted and everything worked great. Thank You!!
I suspect that I'll have to be careful if I change the definition of that data type (add an element, etc) since it is no longer connected to the data type. We'll cross that bridge when we need to.
Thanks again

Shared Variables for Real-TIme Robot Control

I'm really stuck in my efforts to use LV real-time in my hardware control application. I have a 6-axis industrial robot arm that I must control programmatically from my PC. To do this I've developed a dynamic link library of functions for various robot control commands that I can call using Code Interface Nodes in LV (using 8.5). This has worked great, that is, until I tried to port parts of the application to a real-time controller. As it turns out, because the robot control dll is linked with and relies so heavily upon several Windows libraries, it is not compatible with use on a RT target, as verified by the the "DLL Checker" application I downloaded from the NI site. When the robot is not actually executing movements, I am constantly reading/writing analog and digital I/O from various sensors, etc.....
This seemed to suggest that I should simply segregate my robot commands from the I/O activities, using my host PC for the former, and my deterministic RT loop on the target machine for the latter. I set up a Robot Controller Server (RCS) vi running on my host PC that is continuously looking for (in a timed loop) a flag (a boolean) to initiate a robot movement command. Because several parameters are used to specify the robot movement, I created a custom control cluster (which includes the boolean variable) that I then used to make a Network Shared Variable that can be updated by either the RT target or the host PC running the RCS. I chose NOT to use buffering, and FIFO is not available with shared variables based on custom controls.
Here's sequence of events I'd like to accomplish:
1) on my host PC I deploy the RCS, which continuously pools a boolean variable in the control cluster that would indicate the robot should move. The shared variable cluster is initialized in the RBS and the timed loop begins.
2) I deploy the RT vi, which should set the boolean flag in the control cluster, then update the shared variable cluster.
3) an instance of the control cluster node in the RCS should update, thereby initiating a sequence of events in a case structure. (this happens on some occassions, but very few)
4) robot movement commands are executed, after which the boolean in the control cluster is set back to its original value.
5) the RT vi (which is polling in a loop) should see this latest change in the boolean as a loop stop condition and continue with the RT vi execution.
With the robot controller running in a timed loop, it occassionally "sees" and responds to a change of value in members of the shared variable cluster, but most times it does not. Furthermore, when the robot controller vi tries to trigger that the movement has completed by changing a boolean in the control cluster, the RT vi never sees it and does not respond.
1) Bad or inappropriate use of network shared variables?
2) a racing issue?
3) slow network?
4) should I buffer the control cluster?
5) a limitation of a custom control?
6) too many readers/writers?
7) should I change some control cluster nodes to relative, rather than absolute?
8) why can't I "compile" my RT vi into an executable?
Any help would be greatly appreciated. Unfortunately, I'm writing this from home and cannot attach vi files or pictures, but would be happy to do so at work tomorrow. I'm counting on the collective genius in the universe of LV users and veterans to save my bacon.....
David

Hi David,
I'm curious why you decided to build a CIN instead of developing the code in
LabVIEW. Is there some functionality that that LabVIEW couldn't
provide? Can you provide some more information about the LabVIEW
Real-Time target you're using? What type of IO are you using?
It is impossible to get LabVIEW Real-Time performance on a desktop PC running
an OS other than LabVIEW Real-Time. Even running a timed loop in LabVIEW
for Windows won't guarantee a jitter free application. Also, no TCP based
network communication can be deterministic. This means Network Shared
Variables are also not deterministic (they use a TCP for data transport) and I
advise against using them as a means to send time critical control data between
a Windows host and a LabVIEW Real-Time application.
In general, I would architect most LabVIEW-based control applications as
follows:
- Write all control logic and IO operations in LabVIEW Real-Time. The
LabVIEW Real-Time application would accept set points and/or commands from the
'host' (desktop PC). The Real-Time controller should be capable of
running independently or automatically shutting down safely if communication to
the PC is lost.
- Write a front-end user interface in LabVIEW that runs on the desktop
PC. Use Shared Variables with the RT-FIFO option enabled to send new set
points and/or commands to the LabVIEW Real-Time target.
Shared variable buffering and RT-FIFOs can be a little confusing. Granted
not all control applications are the same, but I generally recommend against
using buffering in control applications and in LabVIEW Real-Time applications
recommend using the RT-FIFO option. Here's why: Imagine you have a
Real-Time application with two timed loops. Time-loop 'A' calculates the
time critical control parameters that get written to hardware output in
timed-loop 'B'. Loop 'A' writes the outputs to a RT-FIFO enabled variable
with a RT-FIFO length of 50. Loop 'B' reads the outputs from the shared
variable, but for some reason, if loop 'B' gets behind then the shared variable
RT-FIFO will now contain several extra elements. Unless loop 'b' runs
extra fast to empty the RT-FIFO, loop 'B' will now start outputting values that
it should have output on previous cycles. The actual desired behavior is
that loop 'B' should output the most recent control settings, which means you
should turn off buffering and set the RT-FIFO length to 1.
There is also a clear distinction between buffering and the RT-FIFO
option. The RT-FIFO option is used to add a non-blocking layer between
network communication and time-critical code in LabVIEW Real-Time
applications. It also provides a safe mechanism to share data between two
loops running in a Real-Time application without introducing unnecessary
jitter. Network buffering is a feature that allows a client to receive
data change updates from the server even if the client is reading the variable
slower than the server is writing to it. In the example I presented above
you don't need to enable networking because the shared variable is used
entirely within the Real-Time application. However, it would be
appropriate to send control set points from a Windows PC to the Real-Time
application using network published shared variables with the RT-FIFO option
enabled. If it is critical that the Real-Time application executed all
commands in the sequence they were sent then you could enable an appropriate
buffer. If the control application only needs the latest set point
setting from the Windows host then you can safely disable network buffering
(but you should still enable the RT-FIFO option with a length of 1 element.)
Network buffering is especially good if the writer is 'bursty' and the reading
rate is relatively constant. In the robot application I can imagine buffering
would be useful if you wanted to send a sequence of timed movements to the
Real-Time controller using a cluster of timestamp and set point. In this
case, you may write the sequence values to the variable very quickly, but the
Real-Time controller would read the set points out as it proceeded through the movements.
The following document presents a good overview of shared variable
options: http://zone.ni.com/devzone/cda/tut/p/id/4679
-Nick
LabVIEW R&D
~~

Does a network published shared variable drop the waveform attributes?

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