FRC 2020

Team 254's 2020 FRC robot code for Dreadnought. Dreadnought's code is written in Java and is based off WPILib's Java control system.

The code is divided into several packages, each responsible for a different aspect of the robot function. This README explains setup instructions, the function of each package, and some of the variable naming conventions used. Additional information about each specific class can be found in that class' Java file.

Setup Instructions

General

1. Clone this repo
2. Run ./gradlew to download Gradle and needed FRC/Vendor libraries (make sure you're using Java 11 or greater)
3. Run ./gradlew downloadAll to download FRC tools (ShuffleBoard, etc.)
4. Run ./gradlew tasks to see available options
5. Enjoy!

Visual Studio Code (Official IDE)

1. Get the WPILib extension from the release page on this repository
2. In .vscode/settings.json, set the User Setting, java.home, to the correct directory pointing to your JDK 11 directory

IntelliJ

1. Run ./gradlew idea
2. Open the FRC-2020.ipr file with IntelliJ
3. When prompted, select import Gradle build

Eclipse

1. Run ./gradlew eclipse
2. Open Eclipse and go to File > Open Projects from File System...
3. Set the import source to the FRC-2020 folder then click finish

Basic Gradle Commands

• Run ./gradlew deploy to deploy to the robot in Terminal (*nix) or Powershell (Windows)
• Run ./gradlew build to build the code. Use the --info flag for more details
• Run ./gradlew test to run all of the JUnit tests

Code Highlights

• Path following with a RAMSETE nonlinear feedback controller and splines

  To control autonomous driving, a nonlinear feedback controller is utilized to follow paths constructed of quintic Hermite splines.

• Image undistortion with OpenCV

  To correct lens distortion, OpenCV is used to map distorted or "raw" pixel coordinates to undistorted or "real" coordinates. These maps are precomputed for each individual Limelight and deployed with the rest of the code to reduce in-game computation time.

• Camera characterization with OpenCV

  To determine each camera's distortion constants, this script is used. Essentially, pictures of a checkerboard are taken at various distances and angles with each Limelight camera, then their cameras are characterized by the OpenCV script (this guide goes into more detail). Derived constants are then copied into LimelightConstantsFactory and used to generate each UndistortMap.

• Climbing with PTO drive gearbox

  The PTO climbing mechanism is controlled by a state machine which handles transitioning between climbing stages.

• Automatic Power Cell serializer

  To prevent jams when intaking, a serializer controlled by a state machine automatically sweeps Power Cells away from the intake area. It also feeds balls one by one up a ramp into the shooter.

Package Functions

• com.team254.frc2020

  Contains the robot's central functions and holds a class with all numerical constants used throughout the code.

• com.team254.frc2020.auto

  Handles the execution of autonomous routines and contains the actions and modes packages

• com.team254.frc2020.auto.actions

  Contains all actions used during the autonomous period, which all share a common interface, Action (also in this package). Examples include driving paths, auto aiming the turret and scoring. Actions interact with the subsystems, which in turn interact with the hardware.

• com.team254.frc2020.auto.modes

  Contains all autonomous modes. Autonomous modes consist of a list of autonomous actions executed in a specific order.

• com.team254.frc2020.controlboard

  Contains code for the driver to use either joysticks or gamepad and the operator to use a gamepad. Also contains a wrapper class specifically for Xbox controllers (see XboxController.java).

• com.team254.frc2020.limelight

  Handles interactions with Limelight.

• com.team254.frc2020.limelight.constants

  Contains various constants for Limelights, including physical constants and pipeline information.

• com.team254.frc2020.limelight.undistort

  Contains code for undistorting images, including undistortion maps which implement the UndistortMaps interface and essentially map "distorted" (raw) pixels to their "undistorted" equivalents.

• com.team254.frc2020.loops

  Contains codes for loops, which are routines that run periodically on the robot, such as for calculating robot pose, processing vision feedback, or updating subsystems. All loops implement the Loop interface and are handled (started, stopped, added) by the Looper class, which runs at 100 Hz. The Robot class has one main looper, mEnabledLooper, that runs all loops when the robot is enabled.

• com.team254.frc2020.paths

  Contains the generator for all the trajectories that the robot can drive during the autonomous period.

• com.team254.frc2020.planners

  Contains planners for various types of motion.

• com.team254.frc2020.statemachines

  Contains the state machines for various subsystems.

• com.team254.frc2020.states

  Contains states and other classes used in various subsystem and state machine classes.

• com.team254.frc2020.subsystems

  Contains code for subsystems, which are consolidated into one central class per subsystem, all of which extend the Subsystem abstract class. Each subsystem uses state machines for control and is a singleton, meaning that there is only one instance of each. Subsystems also contain an enabled loop, a read periodic inputs method, and a write periodic outputs method, which are controlled by the SubystemManager class.

• com.team254.lib.drivers

  Contains a set of custom classes for motor controllers (TalonSRX's and Talon FX's) that include classes for creating motor controllers with factory default settings, handling errors, reducing CAN Bus usage, and checking motors.

• com.team254.lib.geometry

  Contains a set of classes that represent various geometric entities.

• com.team254.lib.motion

  Contains all motion profiling code used for autonomous driving. Trapezoidal motion profiles are used for smooth acceleration and minimal slip.

• com.team254.lib.physics

  Contains classes that model physical systems and their low level behavior (as opposed to high level subsystems).

• com.team254.lib.spline

  Contains code for generating and optimizing splines.

• com.team254.lib.trajectory

  Contains code for following and storing trajectories.

• com.team254.lib.util

  Contains a collection of assorted utilities classes used in the robot code. Check each file for more information.

• com.team254.lib.vision

  Contains various classes that help with tracking and storing information about vision targets.

• com.team254.lib.wpilib

  Contains parent classes of the main Robot class that get rid of loop overrun and watchdog print messages that clutter the console.

Style Conventions

• k*** (i.e. kDriveWheelTrackWidthInches): Final constants, especially those found in the Constants.java file
• m*** (i.e. mPathFollower): Private instance variables