CAN Jaguar Wiring with RoboRIO

We are looking into using our team’s old Jaguars this year, and are thinking of switching over to CAN. With the new dedicated CAN port on the RoboRIO, I’m a little confused about the wiring.

It seems that previously, a CAN bus would contain 4 wires (+, 2 CAN, and Ground) which would connect the 6P4C plugs on the Jags.

Now the CAN signal out of the RoboRIO comes on just the 2 CAN lines. Will we need to just plug these two into the 6P4C plug without any + and ground lines, or do those need to come from the PDP for the first Jag in the line?


You don’t need the positive or ground wires.
Just the two CAN H and CAN L wires.

Simple as that! I assume they will need to receive a firmware update then?

They work this way without a firmware update. It’s just how the hardware works. CAN is a 2-wire bus.
There will be an unrelated firmware update for both the Black & Gray Jaguars though.

As a caveat…
Please make a decent two wire to four wire transition for your Jag link and be sure that the bus is terminated properly, at the and of the bus.

What do you mean by " a decent two wire to four wire transition"? How do you define this?

Brian Utterback

All CTRE CAN devices are two wires for CAN. Running ground along with CAN is potentially bad. Imagine a Jag driving a load, then suddenly it loses it’s ground connection (bad Anderson or black screw terminal loose). Now you have a motor load sourcing current through the Jag’s tiny digital ground on the RJ11. Great way to fry wires.

The Jags have a four wire RJ11 jack for CAN interface. In the past, the majority of CAN related issues related to teams making this connection and the buss termination to these jacks improperly.