Unexplained intermittent CAN / 2CAN Jaguar problems at GSR

[Mike Copioli]

We have also experienced the -44087 error along with the same host of symptoms, It happened once during a practice match and never during an actual match. We of course are using a 2CAN and have only seen the issue when it is used in FRC (cRIO, FRC JAG firmware 92). We have not seen the issue when the 2CAN is being used in the Crosslink Control System. It does seem to be a race condition based on the observed behavior and difficulty reproducing the failure. I have reported the problem to Omar and he has been unable to reproduce the issue. The fact that a soft reboot of the cRIO fixes the issue, and the problem has been seen in both the serial and Ethernet gateways, leads me to believe the problem is above the gateway level. We will continue to test using the 2CAN and advise if there are any bugs found on the side of the 2CAN.

[Hugh Meyer]

Last year we experienced several issues using CAN and lag was one of them.

We connected an oscilloscope to two digital outputs. One scope channel was controlled by software code that turned on at the start and off at the end of our periodic loop. The other channel was driven by a toggle function at the beginning of our code. This helped to define the state and made a good trigger signal.

We found that our code was taking longer than our periodic time. Not a good situation. The problem occurred because of the CAN communications. We were driving 8 Jaguars and polling for just about all the data we could, so we could log the data.

As a result we multiplexed the data out over 4 periods. This reduced our code run time down to about 55 milliseconds. We run our periodic loop at 100 milliseconds.

This arrangement has been institutionalized this year with a special cable that connects directly to the break out board and scope. We regularly verify that the code is running under the period.

A change we made from last year was ground loop isolation. Remove the ground wire in the CAN cable. This is a direct ground loop mess. If you are using one encoder to drive two Jaguars you will need optical isolation to remove the ground loop.

Another change is that we added filtering on the Jaguar at the encoder connector. We were seeing resets on the Jaguars and the filter seems to be the solution. Resets will cause all kinds of problems.

I have posts regarding these issues on other threads.

We are using a 2CAN and C++. The serial port baud rate of 115k was just not fast enough to transfer all the data we wanted to transfer.

We don’t have all of the issues fixed, but I wanted to share these in hopes that it will help others using CAN Jaguar.

Good luck!

-Hugh