The Basics
In the words of WPI: “Motor controllers come in two main flavors: CAN and PWM. A CAN controller can send more detailed status information back to the roboRIO, whereas a PWM controller can only be set to a value.” Basically, CAN controllers are two-way: information is sent to the controller, and the controller provides data back. Meanwhile, PWM controllers are one-way: information is sent to the controller. All of the code on the WPI website uses a PWM controller, including the code in the example projects. Code for CAN devices are provided by the website that produces the CAN controller you’re working with.
Our robot uses Rev SPARK MAX motor controllers. Rev provides a list of projects showing implementation of stuff like SPARK MAX motor controllers and the Power Distribution Hub1. To use this code, you need to install Rev’s vendor dependency, which allows you to import the com.revrobotics package into your code and use objects like CANSparkMax. See here for info about vendor dependencies and how to install them.
link to 2024 online vendor dependency install: https://software-metadata.revrobotics.com/REVLib-2024.json
SPARK MAX Controllers
(CANSparkMax docs)
Spark Max Controllers use CAN and function similar to the PWM motor controllers that utilize the built-in FRC class PWMMotorController. Motor controllers in general allow programmers to vary the amount of voltage delivered to a motor. Motor controllers are what we actually control in code, not the motors. Our code doesn’t care whether we use a Neo 550 or a Neo as our motor, it just cares that it’s connected to a Spark Max controller.
It’s actually pretty simple to use Spark Max controllers in a normal differential drive robot, but it gets complicated for swerve drive robots. ==So absolutely use the Spark Max Swerve Drive example project.==
The other Spark Max example projects are helpful to control various Spark Max functions in code, like reading values from its encoder or getting bus measurements.