FRC 2018

Team 254's 2018 FRC robot code for Lockdown. Lockdown's code is written in Java and is based off of 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

Clone this repo
Run ./gradlew to download gradle and needed FRC libraries
Run ./gradlew tasks to see available build options
Enjoy!

Eclipse

Run ./gradlew eclipse
Open Eclipse and go to "File > Open Projects" from "File System..."
Set the import source to the FRC-2018-Public folder then click finish

IntelliJ

Run ./gradlew idea
Open the FRC-2018-Public.ipr file with IntelliJ

Building/Deploying to the Robot

Run ./gradlew build to build the code. Use the --info flag for more details
Run ./gradlew deploy to deploy to the robot in Terminal (Mac) or Powershell (Windows)

Code Highlights

Building with Gradle

Instead of working with Ant, we used GradleRIO, which is a powerful Gradle plugin that allows us to build and deploy our code for FRC. It automatically fetches WPILib, CTRE Toolsuite, and other libraries, and is easier to use across different IDEs.
Path following with a nonlinear feedback controller and splines

To control autonomous driving, the robot utilizes a nonlinear feedback controller and drives paths constructed of quintic Hermite splines.
Path generation and visualization via Java app

Cheesy Path, a Java webapp, allows a user to quickly and easily create and visualize autonomous paths. It is located in the src/main/webapp directory and the com.team254.path package. Run with ./gradlew tomcatRunWar and open http://localhost:8080. To stop the server, run ./gradlew tomcatStop.
Self-test modes for each subsystem

Each subsystem contains a checkSystem() method that tests motor output currents and RPMs. These self tests allow us to quickly verify that all motors are working properly.
Scale detection

Cheesy Vision 2.0 is a Python app that uses OpenCV to track the angle of the scale. The app is meant to be run on the driver station computer and uses an external USB webcam pointed through the driver station glass at the scale. This allows us to set our elevator to the right height during autonomous and prevent wasting time by raising it higher than necessary, which we found was needed to complete a 4 cube auto within the time limit.
Lidar Processing

Even though this was not used on the final iteration of our robot code, we are still releasing our lidar processing code. This consisted of ICP algorithms to detect the scale within the points detected and sent by the Slamtec RPLIDAR A2 and can be found in the com.team254.frc2018.lidar package. Our RPLIDAR driver can be found here.

Package Functions

com.team254.frc2018

Contains the robot's central functions and holds a file with all numerical constants used throughout the code. For example, the Robot class controls all routines depending on the robot state.
com.team254.frc2018.auto

Handles the execution of autonomous routines and contains the actions, creators, and modes packages.
com.team254.frc2018.auto.actions

Contains all actions used during the autonomous period, which all share a common interface, Action (also in this package). Examples include shooting cubes, driving a trajectory, or moving the elevator. Routines interact with the Subsystems, which interact with the hardware.
com.team254.frc2018.auto.creators

Contains all the auto mode creators, which select the correct auto mode to run based on user input and FMS data.
com.team254.frc2018.auto.modes

Contains all autonomous modes. Autonomous modes consist of a list of autonomous actions executed in a certain order.
com.team254.frc2018.controlboard

Contains all the code for the different control boards. This allows any combination of driver station joysticks, button board, and Xbox Controllers to be used for both driving and operating. These are controlled by booleans in Constants.java.
com.team254.frc2018.lidar

Contains classes that are used to communicate with the Slamtec RPLIDAR A2 and to store and process points sent by the lidar.
com.team254.frc2018.lidar.icp

Contains the algorithms for processing points sent by the lidar.
com.team254.frc2018.loops

Loops are routines that run periodically on the robot, such as 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 200 Hz. The Robot class has one main looper, mEnabledLooper, that runs all loops when the robot is enabled.
com.team254.frc2018.paths

Contains the generator for all of the trajectories that the robot drives during autonomous period.
com.team254.frc2018.planners

Loops are routines that run periodically on the robot, such as 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 200 Hz. The Robot class has one main looper, mEnabledLooper, that runs all loops when the robot is enabled.
com.team254.frc2018.statemachines

Contains the state machines for the intake and overall superstructure.
com.team254.frc2018.states

Contains states and other classes used in the subsystem and state machine classes.
com.team254.frc2018.subsystems

Subsystems are consolidated into one central class per subsystem, all of which extend the Subsystem abstract class. Each subsystem uses state machines for control. Each subsystem is also a singleton, meaning that there is only one instance of each. To modify a subsystem, one would get the instance of the subsystem and change its state. The Subsystem class will work on setting the desired state.
com.team254.lib.drivers

Contains a set of custom classes for TalonSRXs.
com.team254.lib.geometry

Contains a set of classes that represent various geometric entities.
com.team254.lib.physics

Contains classes that model DC motor transmissions and differential drive characterization.
com.team254.lib.spline

Contains the code for generating and optimizing splines.
com.team254.lib.trajectory

Contains classes for following and storing trajectories.
com.team254.lib.trajectory.timing

Contains classes for fitting trajectories with time profiles.
com.team254.lib.util

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

Variable Naming Conventions

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