Creating Project Files#

Lets get started

Overview#

Before we can start programing a robot, we must create a new project in Visual Studio Code (VSCode).

See table of contents for a breakdown of this section.

Creating a New Project#

Default Project Contents#

Newly created projects have many files within them. We only care about the contents within the src/main/java/frc/robot/ folder. Everything else can be ignored at this point in the tutorial.

Files in the robot folder:

• ExampleCommand.java
  • An example Command
• ExampleSubsystem.java
  • An example SubSystem
• Constants.java (new in 2020, replaces RobotMap.java)
  • Used to map physical ports (digital if using the CAN bus) of sensors or devices connected to the robot and assign them a variable name to be used in other parts of the code.
    • This provides flexibility for changing wiring, makes checking the wiring easier, and significantly reduces the number of magic numbers floating around.
  • Can also be used to store generic constant values as variables in the code
• Main.java
  • Used for advanced programming
  • Will be ignored/left as is for this tutorial
• RobotContainer.java (new in 2020, replaces OI.java)
  • Used to declare our subsystem
  • Used to create a connection between commands and Operator Interfaces (OI) such as Joysticks or buttons
• Robot.java
  • The main class of the robot which is run when a robot boots up.
  • Used to run special methods in the init and period phases of the auto, teleop, and disabled states

Creating a New Subsystem#

Adding the Subsystem to RobotContainer.java#

Now when we use this subsystem in commands, we must call RobotContainer.m_desiredSubsystemName. to get access to it and its methods. (i.e. RobotContainer.m_drivetrain.someMethod())

Default Subsystem Contents#

Newly created subsystems are empty with the exception of the periodic.

• Currently there is no constructor, we will create a constructor ourselves later.
• periodic - a method that will be called periodically (once per robot scheduler run)
  • Useful for adding/updating data to Driverstation dashboard
  • Useful updating variables that need to always up to date

package frc.robot.subsystems;

import edu.wpi.first.wpilibj2.command.SubsystemBase;

public class Drivetrain extends SubsystemBase {
  /**
   * Creates a new Drivetrain.
   */
  public Drivetrain() {

  }

  @Override
  public void periodic() {
    // This method will be called once per scheduler run
  }
}

Creating a New Command#

Default Command Contents#

Newly created commands have some predefined methods in them specific for a command based robot.

• Constructor - Called when the robot program is FIRST loaded.
  • Subsystem dependencies are declared here.
• initialize() - Called ONCE just before this Command runs the first time.
• execute() - Called REPEATEDLY when this Command is scheduled to run
• end() - Called ONCE after isFinished returns true or when another command which requires one or more of the same subsystems is scheduled to run
• isFinished() - Make this return TRUE when this Command no longer needs to run execute() (initialize always runs once regardless).

package frc.robot.commands;

import edu.wpi.first.wpilibj2.command.CommandBase;

public class DriveArcade extends CommandBase {
  /**
   * Creates a new DriveArcade.
   */
  public DriveArcade() {
    // Use addRequirements() here to declare subsystem dependencies.
  }

  // Called when the command is initially scheduled.
  @Override
  public void initialize() {
  }

  // Called every time the scheduler runs while the command is scheduled.
  @Override
  public void execute() {
  }

  // Called once the command ends or is interrupted.
  @Override
  public void end(boolean interrupted) {
  }

  // Returns true when the command should end.
  @Override
  public boolean isFinished() {
    return false;
  }
}