[examples] Adding XRP java and cpp examples for Timed Robot (#8599)

Adding an example (one C++ and one Java) for using TimedRobot with the
XRP.

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/examples.json

@@ -812,6 +812,22 @@
       "xrp"
     ]
   },
+  {
+    "name": "XRP Timed",
+    "description": "An very basic timed robot program that can be used with the XRP reference robot design.",
+    "tags": [
+      "XRP",
+      "Differential Drive",
+      "XboxController"
+    ],
+    "foldername": "xrptimed",
+    "gradlebase": "javaxrp",
+    "mainclass": "Main",
+    "commandversion": 2,
+    "extravendordeps": [
+      "xrp"
+    ]
+  },
   {
     "name": "Digital Communication Sample",
     "description": "Communicates with external devices (such as an Arduino) using the roboRIO's DIO.",

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/xrptimed/Main.java

@@ -0,0 +1,25 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.wpilibj.examples.xrptimed;
+
+import edu.wpi.first.wpilibj.RobotBase;
+
+/**
+ * Do NOT add any static variables to this class, or any initialization at all. Unless you know what
+ * you are doing, do not modify this file except to change the parameter class to the startRobot
+ * call.
+ */
+public final class Main {
+  private Main() {}
+
+  /**
+   * Main initialization function. Do not perform any initialization here.
+   *
+   * <p>If you change your main robot class, change the parameter type.
+   */
+  public static void main(String... args) {
+    RobotBase.startRobot(Robot::new);
+  }
+}

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/xrptimed/Robot.java

@@ -0,0 +1,73 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.wpilibj.examples.xrptimed;
+
+import edu.wpi.first.util.sendable.SendableRegistry;
+import edu.wpi.first.wpilibj.TimedRobot;
+import edu.wpi.first.wpilibj.Timer;
+import edu.wpi.first.wpilibj.XboxController;
+import edu.wpi.first.wpilibj.drive.DifferentialDrive;
+import edu.wpi.first.wpilibj.xrp.XRPMotor;
+
+/**
+ * The methods in this class are called automatically corresponding to each mode, as described in
+ * the TimedRobot documentation. If you change the name of this class or the package after creating
+ * this project, you must also update the manifest file in the resource directory.
+ */
+public class Robot extends TimedRobot {
+  private final XRPMotor m_leftDrive = new XRPMotor(0);
+  private final XRPMotor m_rightDrive = new XRPMotor(1);
+  private final DifferentialDrive m_robotDrive =
+      new DifferentialDrive(m_leftDrive::set, m_rightDrive::set);
+  private final XboxController m_controller = new XboxController(0);
+  private final Timer m_timer = new Timer();
+
+  /** Called once at the beginning of the robot program. */
+  public Robot() {
+    SendableRegistry.addChild(m_robotDrive, m_leftDrive);
+    SendableRegistry.addChild(m_robotDrive, m_rightDrive);
+
+    // We need to invert one side of the drivetrain so that positive voltages
+    // result in both sides moving forward. Depending on how your robot's
+    // gearbox is constructed, you might have to invert the left side instead.
+    m_rightDrive.setInverted(true);
+  }
+
+  /** This function is run once each time the robot enters autonomous mode. */
+  @Override
+  public void autonomousInit() {
+    m_timer.restart();
+  }
+
+  /** This function is called periodically during autonomous. */
+  @Override
+  public void autonomousPeriodic() {
+    // Drive for 2 seconds
+    if (m_timer.get() < 2.0) {
+      // Drive forwards half speed, make sure to turn input squaring off
+      m_robotDrive.arcadeDrive(0.5, 0.0, false);
+    } else {
+      m_robotDrive.stopMotor(); // stop robot
+    }
+  }
+
+  /** This function is called once each time the robot enters teleoperated mode. */
+  @Override
+  public void teleopInit() {}
+
+  /** This function is called periodically during teleoperated mode. */
+  @Override
+  public void teleopPeriodic() {
+    m_robotDrive.arcadeDrive(-m_controller.getLeftY(), -m_controller.getRightX());
+  }
+
+  /** This function is called once each time the robot enters test mode. */
+  @Override
+  public void testInit() {}
+
+  /** This function is called periodically during test mode. */
+  @Override
+  public void testPeriodic() {}
+}