[examples] Add mecanum drive snippets (#8931)

shows both polar, and cartesian

wpilibcExamples/example_projects.bzl

@@ -72,6 +72,7 @@ SNIPPET_FOLDERS = [
     "I2CCommunication",
     "IntermediateVision",
     "LimitSwitch",
+    "MecanumDrive",
     "MotorControl",
     "OnboardIMU",
     "ProfiledPIDFeedforward",

wpilibcExamples/src/main/cpp/snippets/MecanumDrive/cpp/Robot.cpp

@@ -0,0 +1,78 @@
+// 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.
+
+#include "wpi/drive/MecanumDrive.hpp"
+#include "wpi/driverstation/Joystick.hpp"
+#include "wpi/framework/TimedRobot.hpp"
+#include "wpi/hardware/imu/OnboardIMU.hpp"
+#include "wpi/hardware/motor/PWMSparkMax.hpp"
+
+/**
+ * This is a sample program that uses mecanum drive with a gyro sensor to
+ * maintain rotation vectors in relation to the starting orientation of the
+ * robot (field-oriented controls).
+ *
+ * Finally, short code snippets show how to use cartesian and polar drive
+ * methods for wpilib-docs.
+ * https://docs.wpilib.org/en/stable/docs/software/hardware-apis/motors/wpi-drive-classes.html
+ */
+class Robot : public wpi::TimedRobot {
+ public:
+  Robot() {
+    wpi::util::SendableRegistry::AddChild(&robotDrive, &frontLeft);
+    wpi::util::SendableRegistry::AddChild(&robotDrive, &rearLeft);
+    wpi::util::SendableRegistry::AddChild(&robotDrive, &frontRight);
+    wpi::util::SendableRegistry::AddChild(&robotDrive, &rearRight);
+
+    // Invert the right side motors. You may need to change or remove this to
+    // match your robot.
+    frontRight.SetInverted(true);
+    rearRight.SetInverted(true);
+  }
+
+  /**
+   * Mecanum drive is used with the gyro angle as an input.
+   */
+  void TeleopPeriodic() override {
+    /* Use the joystick Y axis for forward movement, X axis for lateral
+     * movement, and Z axis for rotation, field oriented.
+     */
+    robotDrive.DriveCartesian(-joystick.GetY(), -joystick.GetX(),
+                              -joystick.GetZ(), imu.GetRotation2d());
+    // Drive using the X, Y, and Z axes of the joystick.
+    robotDrive.DriveCartesian(-joystick.GetY(), -joystick.GetX(),
+                              -joystick.GetZ());
+    // Drive at 45 degrees relative to the robot, at the speed given by the Y
+    // axis of the joystick, with no rotation.
+    robotDrive.DrivePolar(-joystick.GetY(), 45_deg, 0);
+  }
+
+ private:
+  static constexpr int kFrontLeftMotorPort = 0;
+  static constexpr int kRearLeftMotorPort = 1;
+  static constexpr int kFrontRightMotorPort = 2;
+  static constexpr int kRearRightMotorPort = 3;
+  static constexpr wpi::OnboardIMU::MountOrientation kIMUMountOrientation =
+      wpi::OnboardIMU::FLAT;
+  static constexpr int kJoystickPort = 0;
+
+  wpi::PWMSparkMax frontLeft{kFrontLeftMotorPort};
+  wpi::PWMSparkMax rearLeft{kRearLeftMotorPort};
+  wpi::PWMSparkMax frontRight{kFrontRightMotorPort};
+  wpi::PWMSparkMax rearRight{kRearRightMotorPort};
+  wpi::MecanumDrive robotDrive{
+      [&](double output) { frontLeft.SetThrottle(output); },
+      [&](double output) { rearLeft.SetThrottle(output); },
+      [&](double output) { frontRight.SetThrottle(output); },
+      [&](double output) { rearRight.SetThrottle(output); }};
+
+  wpi::OnboardIMU imu{kIMUMountOrientation};
+  wpi::Joystick joystick{kJoystickPort};
+};
+
+#ifndef RUNNING_WPILIB_TESTS
+int main() {
+  return wpi::StartRobot<Robot>();
+}
+#endif

wpilibcExamples/src/main/cpp/snippets/snippets.json

@@ -304,6 +304,17 @@
     "foldername": "Solenoid",
     "gradlebase": "cpp"
   },
+  {
+    "name": "Mecanum Drive",
+    "description": "Show mecanum drive control with cartesian and polar drive in teleop.",
+    "tags": [
+      "Mecanum Drive",
+      "Gyro",
+      "Joystick"
+    ],
+    "foldername": "MecanumDrive",
+    "gradlebase": "cpp"
+  },
   {
     "name": "Differential Drive",
     "description": "Show differential drive control with tank, arcade, and curvature drive in teleop",