[robotpy][examples] Split examples and snippets (#8944)

This also updates the bazel scripts to behave more like the C++ and Java
examples, and updates the copybara scripts to be able to sync up
`mostrobotpy`

robotpyExamples/examples/MecanumBot/drivetrain.py

@@ -0,0 +1,129 @@
+#
+# 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.
+#
+import math
+
+import wpilib
+import wpimath
+
+
+class Drivetrain:
+    """Represents a mecanum drive style drivetrain."""
+
+    MAX_VELOCITY = 3.0  # 3 meters per second
+    MAX_ANGULAR_VELOCITY = math.pi  # 1/2 rotation per second
+
+    def __init__(self) -> None:
+        self.frontLeftMotor = wpilib.PWMSparkMax(1)
+        self.frontRightMotor = wpilib.PWMSparkMax(2)
+        self.backLeftMotor = wpilib.PWMSparkMax(3)
+        self.backRightMotor = wpilib.PWMSparkMax(4)
+
+        self.frontLeftEncoder = wpilib.Encoder(0, 1)
+        self.frontRightEncoder = wpilib.Encoder(2, 3)
+        self.backLeftEncoder = wpilib.Encoder(4, 5)
+        self.backRightEncoder = wpilib.Encoder(6, 7)
+
+        self.frontLeftLocation = wpimath.Translation2d(0.381, 0.381)
+        self.frontRightLocation = wpimath.Translation2d(0.381, -0.381)
+        self.backLeftLocation = wpimath.Translation2d(-0.381, 0.381)
+        self.backRightLocation = wpimath.Translation2d(-0.381, -0.381)
+
+        self.frontLeftPIDController = wpimath.PIDController(1, 0, 0)
+        self.frontRightPIDController = wpimath.PIDController(1, 0, 0)
+        self.backLeftPIDController = wpimath.PIDController(1, 0, 0)
+        self.backRightPIDController = wpimath.PIDController(1, 0, 0)
+
+        self.imu = wpilib.OnboardIMU(wpilib.OnboardIMU.MountOrientation.FLAT)
+
+        self.kinematics = wpimath.MecanumDriveKinematics(
+            self.frontLeftLocation,
+            self.frontRightLocation,
+            self.backLeftLocation,
+            self.backRightLocation,
+        )
+
+        self.odometry = wpimath.MecanumDriveOdometry(
+            self.kinematics, self.imu.getRotation2d(), self.getCurrentDistances()
+        )
+
+        # Gains are for example purposes only - must be determined for your own robot!
+        self.feedforward = wpimath.SimpleMotorFeedforwardMeters(1, 3)
+
+        self.imu.resetYaw()
+
+        # 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.
+        self.frontRightMotor.setInverted(True)
+        self.backRightMotor.setInverted(True)
+
+    def getCurrentState(self) -> wpimath.MecanumDriveWheelVelocities:
+        """Returns the current state of the drivetrain."""
+        return wpimath.MecanumDriveWheelVelocities(
+            self.frontLeftEncoder.getRate(),
+            self.frontRightEncoder.getRate(),
+            self.backLeftEncoder.getRate(),
+            self.backRightEncoder.getRate(),
+        )
+
+    def getCurrentDistances(self) -> wpimath.MecanumDriveWheelPositions:
+        """Returns the current distances measured by the drivetrain."""
+        positions = wpimath.MecanumDriveWheelPositions()
+        positions.frontLeft = self.frontLeftEncoder.getDistance()
+        positions.frontRight = self.frontRightEncoder.getDistance()
+        positions.rearLeft = self.backLeftEncoder.getDistance()
+        positions.rearRight = self.backRightEncoder.getDistance()
+        return positions
+
+    def setVelocities(self, velocities: wpimath.MecanumDriveWheelVelocities) -> None:
+        """Sets the desired velocities for each wheel."""
+        frontLeftFeedforward = self.feedforward.calculate(velocities.frontLeft)
+        frontRightFeedforward = self.feedforward.calculate(velocities.frontRight)
+        backLeftFeedforward = self.feedforward.calculate(velocities.rearLeft)
+        backRightFeedforward = self.feedforward.calculate(velocities.rearRight)
+
+        frontLeftOutput = self.frontLeftPIDController.calculate(
+            self.frontLeftEncoder.getRate(), velocities.frontLeft
+        )
+        frontRightOutput = self.frontRightPIDController.calculate(
+            self.frontRightEncoder.getRate(), velocities.frontRight
+        )
+        backLeftOutput = self.frontLeftPIDController.calculate(
+            self.backLeftEncoder.getRate(), velocities.rearLeft
+        )
+        backRightOutput = self.frontRightPIDController.calculate(
+            self.backRightEncoder.getRate(), velocities.rearRight
+        )
+
+        self.frontLeftMotor.setVoltage(frontLeftOutput + frontLeftFeedforward)
+        self.frontRightMotor.setVoltage(frontRightOutput + frontRightFeedforward)
+        self.backLeftMotor.setVoltage(backLeftOutput + backLeftFeedforward)
+        self.backRightMotor.setVoltage(backRightOutput + backRightFeedforward)
+
+    def drive(
+        self,
+        xVelocity: float,
+        yVelocity: float,
+        rot: float,
+        fieldRelative: bool,
+        periodSeconds: float,
+    ) -> None:
+        """Method to drive the robot using joystick info."""
+        chassisVelocities = wpimath.ChassisVelocities(xVelocity, yVelocity, rot)
+        if fieldRelative:
+            chassisVelocities = chassisVelocities.toRobotRelative(
+                self.imu.getRotation2d()
+            )
+
+        self.setVelocities(
+            self.kinematics.toWheelVelocities(
+                chassisVelocities.discretize(periodSeconds)
+            ).desaturate(self.MAX_VELOCITY)
+        )
+
+    def updateOdometry(self) -> None:
+        """Updates the field-relative position."""
+        self.odometry.update(self.imu.getRotation2d(), self.getCurrentDistances())

robotpyExamples/examples/MecanumBot/robot.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+#
+# 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.
+#
+
+import wpimath
+import wpilib
+
+from drivetrain import Drivetrain
+
+
+class MyRobot(wpilib.TimedRobot):
+    def __init__(self) -> None:
+        super().__init__()
+
+        self.controller = wpilib.NiDsXboxController(0)
+        self.mecanum = Drivetrain()
+
+        # Slew rate limiters to make joystick inputs more gentle; 1/3 sec from 0 to 1.
+        self.xvelocityLimiter = wpimath.SlewRateLimiter(3)
+        self.yvelocityLimiter = wpimath.SlewRateLimiter(3)
+        self.rotLimiter = wpimath.SlewRateLimiter(3)
+
+    def autonomousPeriodic(self) -> None:
+        self.driveWithJoystick(False)
+        self.mecanum.updateOdometry()
+
+    def teleopPeriodic(self) -> None:
+        self.driveWithJoystick(True)
+
+    def driveWithJoystick(self, fieldRelative: bool) -> None:
+        # Get the x velocity. We are inverting this because Xbox controllers return
+        # negative values when we push forward.
+        xVelocity = (
+            -self.xvelocityLimiter.calculate(self.controller.getLeftY())
+            * Drivetrain.MAX_VELOCITY
+        )
+
+        # Get the y velocity or sideways/strafe velocity. We are inverting this because
+        # we want a positive value when we pull to the left. Xbox controllers
+        # return positive values when you pull to the right by default.
+        yVelocity = (
+            -self.yvelocityLimiter.calculate(self.controller.getLeftX())
+            * Drivetrain.MAX_VELOCITY
+        )
+
+        # Get the rate of angular rotation. We are inverting this because we want a
+        # positive value when we pull to the left (remember, CCW is positive in
+        # mathematics). Xbox controllers return positive values when you pull to
+        # the right by default.
+        rot = (
+            -self.rotLimiter.calculate(self.controller.getRightX())
+            * Drivetrain.MAX_ANGULAR_VELOCITY
+        )
+
+        self.mecanum.drive(xVelocity, yVelocity, rot, fieldRelative, self.getPeriod())