CanStar for Swerve?

[Bmongar]

We are looking at ways to clean up our wiring.

I was considering attaching 1 of these Playing With Fusion CanStar-4 to each of our SDS MK4 swerve modules.

We run a Canivore for our swerve (the 8 motors, 4 encoders, and Pigeon 2). Which says stubs need to be short. I don’t think that would be a problem as we could mount fairly close.

My question is each of the 3 devices has 2 CAN pairs. So when wiring to a CANStar I assume each device attaches to one of the middle terminals with 1 pair each. The main CAN loop attach to the terminals on the sides. What do I do with the second pair from each device? Do I put terminating resisters? Close them together? Cut fairly short and tape the ends so they don’t contact anything?

[ngreen]

No, on the terminating resistors. For this you’d just have to put the single terminating resistor at the last connected can star.

For extra wire pairs, we’ve had no problems to electrical tape ends and bundle the excess in past, but clipping them short and separating them w/ tape is also acceptable. Removing the extra stub is better for the signal, but we didn’t have issues, and that let us go back if we wanted.

[Emerson1706]

You do not want terminating resistors on the ends the way I understand it. I would tape the ends of the unused pair at the end of each star branch.

[Zook]

Nice product. We’ve been using these for a bit:
http://www.mindsensors.com/frc/184-splitter-for-can-network

Costs more per CAN connection, but also have a jumpered terminating resistor built in.

[nuttle]

Since you are using CAN FD (CTRE ecosystem), you will probably want to take a look here:

[Also, page 49 of Falcon 500 User Guide and other CTRE docs.]

The take-away is that, while clean CAN wiring is great, it is important to pay attention to these details. Another option might be to directly wire one of the CAN cables (twisted pairs) from each motor to the encoder, then to wire the other CAN cables from each motor as part of the longer CAN run. Still has only two CAN cables for each swerve module, and there’s one less part in the wiring…

I think the set up you are describing can certainly work, but it’s somewhat sub-optimal, if not done very well.

[asid61]

Star CAN will not play nice with CAN FD. Stick to the slower Roborio bus if you want to mess with CAN topology.

[bdaroz]

We used the MK4s this year and made this piece to hold the associated hardware:

https://www.printables.com/model/98693-motor-controller-mount-for-sds-mk4-swerve-drive-fr

We used these on the module to connect the CAN devices together:

CAN Connector (5 Pack)

[s-neff]

Do you really gain anything by adding the canstar here?

Going falcon-encoder-falcon on each corner gets you to one wirepair in and one wirepair out, assuming soldering the falcons directly into the encoder rather than using interstitial connectors.

Sure you could use connectors, but I wouldn’t. Connectors are for planning to swap components, just bring 5 modules and swap whole modules when failures occur. That gives you time and access to solder the falcon-cancoder connections.