FRC > Electrical

CAN Bus/Network

Contributors:

Nate Johnson

Introduction

A brief summary of how the CAN Bus on an FRC robot works, alongside how to wire the main CAN bus and connect a device

Introduction

Section 1: What is CAN

CAN Networks

BUS Topology

Section 2: How to wire it in

RIO to PDH wiring

Tapping off

Section 1: What is CAN

CAN Networks

CAN (Controller Area Network) runs off a system of low and high voltages, which are electrical waves. This is then interpreted by all of the devices on the network as a 1 (when the wave is high) and a 0 (when the wave is low)

BUS Topology

Our CAN system uses a bus topology. This means that the CAN Network starts from one termination (the RIO or CANivore in our case) and moves to another termination (the PDH in our case). Then every device that needs to access the network taps off the main bus, making the network as robust as it can be.

Section 2: How to wire it in

RIO to PDH wiring

Twist two 22 AWG green and yellow wires and then ferrule them to put into the highlighted section of the RIO to start off the CAN Bus

To terminate the bus, first, make sure that the switch on the PDH for the terminating resistor is ON, then strip off a little bit of the ends of both CAN bus wires, and put them into the highlighted section of the PDH

Tapping off

First, use a posi-tap to tap into the CAN bus by unscrewing the bottom and putting it onto one of the two main bus wires. Then, screw down the actual body of the posi-tap to puncture the bus.

To connect a device, like a motor or sensor, strip and then twist the two green and yellow wires together, pairing yellow with yellow and green with green. Then take off the top of the posi-tap and shove it past the insulation of both pairs. Finally, in one motion, both twist and push the tap and wires into the posi-lock to secure the wires in and connect the device into the bus

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