RT <-> Host communication

[el-diablo]

Hello,
i am facing the following problem:
I have realized the control of a process, with the help of the pid controller, which is included in the LabView Control Design & Simulation module.
A host computer is connected with the cRIO 9074 via Ethernet. At the host computer the user should be able to choose a setpoint or view the actual process value and the output value of the controller at a graph.
I’m using two loops on the RT Target, the first one for the time critical controlling and the second one for the communication with the host. The control loop needs a sampling interval of maximum 2ms. At first i tried to set the period of the communication loop to 5ms. But after that the Host VI lost the connection to the cRIO. So i reduced the period to 100ms and the communication worked again, which is enough for my application. But the problem is that i want to show all(more) measured values since the last communication at the graph and not only the measured values, when communication takes place. So i think that i need some kind of a buffer. Or is it possible to decrease the interval of communication without loosing the connection.
I’ve read already this tutorial: https://www.ni.com/en/support/documentation/supplemental/06/using-the-labview-shared-variable.html, nevertheless i don’t know how to solve the problem.

I am appreciative for any kind of help.

[SFK]

Hi el-diablo,

LabVIEW Shared Variables are not build to transfer data at rates of 100+ Hz. You will want to use LabVIEW Network Streams to send all the measured data to your host:

https://www.ni.com/en/shop/labview/lossless-communication-with-network-streams--components--archite....

Additional examples for the implementation can be found in LabVIEW's Example Finder.

Best regards,

Sebastian 

[el-diablo]

Thank you very much. I will try this solution.

At first i have to update to version 2010. At moment i am using version 2009. Because of this error, i have to update anyway.

[el-diablo]

Hello again,

i have installed LabView 2010 SP1 and the following modules: 

• Real-Time Module
• FPGA Module
• Control Design and Simulation Module
• MathScript RT Module

Now i have the problem, that i cant compile the FPGA VIs because no compilation tool is installed. I couldnt find such tool, neither on the dvds, which i got from my university, nor at the homepage, where i downloaded the modules.

I have the following dvds:

• LabView Core
• extended development
• NI Device Drivers 

I found a site with an installation instruction, which includes everything. But where can i get this platform dvd?

[SFK]

Hello el-diablo,

if you re-start the setup.exe for the LabVIEW FPGA Module, you should be able to chose wether to also install the Xilinx compiler or not. There are two versions of the Xilinx FPGA Compile Tools to chose from: version 10.5 for the older R-Series cards, and version 11.1 for the newer Virtex-5-based devices.

Are the disks that you received from your university genuine NI-manufactured DVDs, or are they burned disks with the eval downloads? I am not sure if the evaluation install of the LabVIEW FPGA Module contains the Compile Tools, so you might want to ask your university personnel for the "Academic Site License" DVDs that they should have. The Compile Tools will there surely be availabe in the FPGA Module setup as seen in the screenshots that you linked.

Best regards,

Sebastian 

[el-diablo]

Thanks for your help again.

I couldnt find the Xilinx Tools on the disks. But i downloaded and installed both tools from this link at the NI homepage. After that i can compile FPGA VIs again. 🙂

Back to my original problem from the first post: I tried to implement the network streams. But it doesnt really work. Sometimes the user interface receives some values from the rt target, at other times not.

It would be nice if someone could check the two VIs. I removed the additional stuff, so that you can get a fast overview.