CAN reliability

[jhersh]

I'd like to address the implications of the lessons learned for the upcoming season...

Originally Posted by kamocat

• CAN messages take a long time over serial due to the current implementation. (messages wait for errors on the CAN bus before completing). If there is an error, the function takes longer still. There is a driver update expected to help alleviate the issue. I have no data on the 2CAN module.

NI and TI are each working to improve performance of the parts of the system they are responsible for.

As for the timeout, the default timeout for a single device transaction has been reduced from 100ms to a much more reasonable 10ms.

The 2CAN plugin is another place where performance needs to be considered (but has not yet been addressed... support from CTRE is needed).

Originally Posted by kamocat

• There are multiple issues with the Jaguar firmware:
  • Speed is dealt with in RPM (the documentation states revolutions per second). Although only the encoder can be used to calculate speed, the "speed reference" configuration is required. The "Speed" status is reported as zero until the Jaguar has been enabled in speed mode. The speed status reports positive regardless of the direction the encoder is turning.

This was an issue with the library implementation and has been fixed for 2011.

Originally Posted by kamocat

• • The "Position" status is reported as zero until the Jaguar has been enabled in position mode.

Same issue, also fixed for 2011.

Originally Posted by kamocat

• • There is no status message to tell if the Jaguar is enabled or disabled.

This is sort of implied... if you can talk to it and you told it to enable, it's enabled. If it's not enabled, but you told it to be, then you probably can't talk to it to ask it if it's enabled.

Originally Posted by kamocat

• • The "control mode" status is not implemented.

It is for 2011.

Originally Posted by kamocat

• • "Device Query" takes half a second to execute, but returns nothing.

I'm not sure what the utility of this message is... I've never tried it. Are you implementing this yourself?

Originally Posted by kamocat

• The current sensor is only accurate within 1 amp. This makes current control unsuitable for all FRC motors smaller than the CIM.

This is a known feature request at TI. No change in this respect for 2011.

Originally Posted by kamocat

• There are occasional reliability issues on startup. Sometimes only some of the motor controllers will function. When my auto-configuration utility is running, the quickest way to fix this is to cycle power to the nonfunctioning devices.

I haven't experienced this behavior. Any information that would help reproduce the issue would allow me to investigate.

We are working hard to make using CAN with Jaguar a competitive advantage and not a liability. We need the help of people like you to identify issues and bring them to our attention.

Thanks for all of your investigation and feedback!

-Joe