roboRIO connection problem and PWM noise

[Jones2bones]

We are having issues connection to the roboRIO after a restart.

When we first connect and deploy the code, the deployment is successfull, but shortly after it loses the connection. We have to wait for about 2 minutes, before it will connect again and then it works fine untill next restart.

We noticed that the RSL light is turned on when we first connect, and the second time it is turned off.

Furthermore more, we are experiencing noise on the PWM signals. When the continuous servo motor is supposed to remain steady, it moves in small steps.

The signal cables is shielded from other cables, so they don’t interfere

We are running Laview 2016 with RoboRIO toolkit.

Any suggestions? 

[oscarfonseca]

Hello Jones2bones,

Thanks for writing in the NI online community!

The lack of communication after you deploy code and when the device restarts sounds to me as a combination of both LabVIEW Real-Time loading the new code, as well as a high CPU usage in the roboRIO (which makes the target disconnect, since the network interface has lower priority).

Regarding the PWM noise, I am unsure on how you have diagnosed the problem, so I can't add much. Does the servo motor work when you use a function generator instead of the roboRIO? Have you scoped the PWM line to see that, in fact, the problem is the line and not the motor controller you have attached in the other side of the roboRIO? Which function/VI are you using to generate your PWM signal (is it in the Real-Time code or the FPGA)?

I hope this information helps you move forward with your project.

All the best,