CAN Jaguar Wiring with RoboRIO

[Joe Wilson]

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?

Thanks
-J

[Mark McLeod]

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

[Joe Wilson]

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

[Mark McLeod]

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.

[Al Skierkiewicz]

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.

[blu28]

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

Brian Utterback

[ozrien]

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.

[Al Skierkiewicz]

Blu,
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.