[examples] Add differential drive snippets (#8927)

Shows tank, arcade, and curvature for wpilib-docs

wpilibcExamples/example_projects.bzl

@@ -58,6 +58,7 @@ SNIPPET_FOLDERS = [
     "AnalogPotentiometer",
     "AprilTagsVision",
     "CANPDP",
+    "DifferentialDrive",
     "DigitalCommunication",
     "DigitalInput",
     "DutyCycleEncoder",

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

@@ -0,0 +1,55 @@
+// 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/DifferentialDrive.hpp"
+#include "wpi/driverstation/Gamepad.hpp"
+#include "wpi/framework/TimedRobot.hpp"
+#include "wpi/hardware/motor/PWMSparkMax.hpp"
+
+/**
+ * DifferentialDrive snippets for wpilib-docs. Runs the motors with tank
+ * drive, arcade drive, and curvature drive.
+ * https://docs.wpilib.org/en/stable/docs/software/hardware-apis/motors/wpi-drive-classes.html
+ */
+class Robot : public wpi::TimedRobot {
+  wpi::PWMSparkMax leftMotor{0};
+  wpi::PWMSparkMax rightMotor{1};
+  wpi::DifferentialDrive robotDrive{
+      [&](double output) { leftMotor.SetThrottle(output); },
+      [&](double output) { rightMotor.SetThrottle(output); }};
+  wpi::Gamepad driverController{0};
+
+ public:
+  Robot() {
+    // 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.
+    rightMotor.SetInverted(true);
+  }
+
+  void TeleopPeriodic() override {
+    // Drive with split arcade style
+    // That means that the Y axis of the left stick moves forward
+    // and backward, and the X of the right stick turns left and right.
+    robotDrive.ArcadeDrive(-driverController.GetLeftY(),
+                           -driverController.GetRightX());
+    // Tank drive with a given left and right rates
+    robotDrive.TankDrive(-driverController.GetLeftY(),
+                         -driverController.GetRightY());
+    // Arcade drive with a given forward and turn rate
+    robotDrive.ArcadeDrive(-driverController.GetLeftY(),
+                           -driverController.GetLeftX());
+    // Curvature drive with a given forward and turn rate, as well as a
+    // quick-turn button
+    robotDrive.CurvatureDrive(-driverController.GetLeftY(),
+                              -driverController.GetLeftX(),
+                              driverController.GetFaceUpButton());
+  }
+};
+
+#ifndef RUNNING_WPILIB_TESTS
+int main() {
+  return wpi::StartRobot<Robot>();
+}
+#endif

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

@@ -303,5 +303,16 @@
     ],
     "foldername": "Solenoid",
     "gradlebase": "cpp"
+  },
+  {
+    "name": "Differential Drive",
+    "description": "Show differential drive control with tank, arcade, and curvature drive in teleop",
+    "tags": [
+      "Differential Drive",
+      "Gamepad"
+    ],
+    "foldername": "DifferentialDrive",
+    "gradlebase": "java",
+    "robotclass": "Robot"
   }
 ]