PWM vs CAN Control

Two control methods#

Motor controllers can be commanded two ways, and the choice affects wiring, capability, and debugging.

PWM (Pulse Width Modulation)#

With PWM, the roboRIO sends a single pulse signal to each controller over a 3-wire cable plugged into one of the roboRIO's PWM ports (0-9). The pulse width (typically 1.0-2.0 ms) tells the controller how fast and which direction to drive.

Pros:

• Simple and easy to understand.
• Easy to troubleshoot - one controller per port.
• No device IDs to configure.

Cons:

• One wire run per controller (lots of wires).
• No feedback data comes back to the roboRIO over PWM.
• Limited to 10 controllers (the number of PWM ports).

WPILib recommends PWM as a starting point because it is less complex and easier to debug.

CAN (Controller Area Network)#

CAN is a digital network that daisy-chains many devices on just two wires (CANH and CANL). The roboRIO, the PD, and every CAN motor controller share the same bus.

Pros:

• Far less wiring - one bus serves dozens of devices.
• Rich two-way data: the controller reports velocity, position, current, temperature, and faults.
• Advanced features: closed-loop control, motion profiling, current limiting, follower mode.
• Easier configuration through vendor tools.

Cons:

• Each device needs a unique CAN ID (set with Phoenix Tuner X for CTR, REV Hardware Client for REV).
• A single broken connection can take down everything downstream on the bus.

Which to choose?#

Most competitive teams use CAN for motor controllers to unlock current limiting and telemetry, while sometimes using PWM for a simple device like an LED blinker driver. Beginners often start with PWM and migrate to CAN as they get comfortable.

Sources#

• WPILib Introduction to FRC Robot Wiring
• WPILib Hardware Component Overview