cRio communication problems

[Nunners]

We have suddenly faced a very weird problem with the programming aspect of our robot. Before I continue, let me state that ALL motor controllers were functioning perfectly as of this morning (~9 AM).

We are still able to communicate with our cRio via ethernet/wireless. We are also able to upload code. However, after our code (which was working perfectly earlier) has been deployed, NONE of our talons receive any input from the sidecar/cRio -- all 9 of them display flashing yellow lights. Spikes are solid yellow.

Any ideas as to how we could troubleshoot this issue? We've reimaged multiple times and even switched out old modules. We are really stuck here.

The only possible cause of this problem that comes to mind is a short or something similar that fried something downstream. A student dragged a PWM cable across the positive and negative ends of a talon while it was powered causing a small spark -- but I highly doubt that would have caused the problems we are currently seeing.

[Mark McLeod]

Nobody touched the PWM cables since 9am?

It's pretty standard troubleshooting to follow the command trail:
Is the Driver Station (DS) showing any errors?
Is the DS Enabled?
If using LabVIEW switch to Test mode on the DS and test a single controller using the Test controls.
Check the three power status lights on the Power Distribution Panel.
Check the three power status lights on the Digital Sidecar (DSC).
Check the status lights on the cRIO (power and status, Ethernet port lights)
Check the 37-pin cable connection that both ends are tight.
Check the orientation of the PWM cables running from the DSC (black to the outside) to the motor controllers (black to the inside).
Test the PWM output at the DSC with a digital multimeter.
Test the motor controller end of the PWM cable with a multimeter.

[Nunners]

Thanks for the response. We have done all of the troubleshooting steps except the ones involving the multimeter. What sort of readings should we expect?

And to answer your question, the PWM cables were disconnected and then reconnected a short time later in the same configuration after we tidied up some of our wiring.

[Alan Anderson]

..A student dragged a PWM cable across the positive and negative ends of a talon while it was powered causing a small spark...

If the black wire on a PWM cable touched battery voltage on a Talon, you might have fried the reverse voltage protection circuit on the Digital Sidecar.