Softmotion on NI myRIO

[Herry78]

Hi,

I want to control several stepper motors (Step/Dir) with myRIO. I calculate points at constant timeintervals on the myRIO. The FPGA generates the step and direction signals.

So far, I have tested only simple straight line moves without acceleration profiles. That is very easy.
Now I have found the Softmotion module and would like to use it to generate the points. Especially because it can also work with arcs and splines. The picture shows the program code for a straigth line move.

As long as I start the VI in developer mode (click on Run), that works. However, if I create an RT application and deploye it on the myRIO, the program will not run.

I found this document, which shows the compatibility with Softmotion. But I think the way I use Softmotion is not discribed here.

http://www.ni.com/product-documentation/53594/en/

Can someone tell me how to use the softmotion with an RT build? Why does this work in developer mode?

Thank you!

[ML927]

Hey Herry,

Have you looked at this document : http://www.ni.com/pdf/manuals/371331d.pdf ?

[Herry78]

Hi ML927,

thanks for your reply!

I know this document. But I can not find a solution for this problem. Sorry, but can you give me a hint?

I know that there are better ways to use softmotion than I do. But the myRIO's FPGA is very small and the projects in the examples do not work.

So I just want to use the trajectory generator offline to calculate the setpoints. The FPGA interpolates between the points and if a threshold value is reached, a step and direction signal is set on output.

Of course, if there are better solutions, I am open to it.

[n_dakota]

Hi @Herry78,

Some set of extra questions:

Are you sure that your real-time deployed application and FPGA starts at all? Maybe some simple LED blinking test?

Could you please confirm that you set it to "Run as startup"? Here you can find how to do it.

Those would be just some quick troubleshooting I'd propose to start with.

[Herry78]

Hi n_dakota,

thank you very much for your reply!

The problem only occurs when softmotion is used in the program.

If I disable the VIs, the program will run correctly. I have tested this with the method you have described. If Softmotion functions (Nodes, ...) are used, I can not switch the LEDs on the myRIO device or the IOs via the FPGA.

I also use shared variables to communicate with a host PC. The value is also not changed if Softmotion is used. I guess the program is not running.

I already use Softmotion on another project with cRIO and AKDs. This works correctly. That's why I'm confused why it does not work in this simple application.

I am grateful for any Tip. I would realy like to solve this problem.

[Herry78]

Does anyone have an idea?