[wpilib] Add EventLoop (#4104)

This is a generic expansion of the command-based Trigger framework.

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

@@ -0,0 +1,26 @@
+// 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.eventloop;
+
+import edu.wpi.first.wpilibj.RobotBase;
+import edu.wpi.first.wpilibj.examples.encoder.Robot;
+
+/**
+ * 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/eventloop/Robot.java

@@ -0,0 +1,91 @@
+// 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.eventloop;
+
+import edu.wpi.first.math.controller.PIDController;
+import edu.wpi.first.math.controller.SimpleMotorFeedforward;
+import edu.wpi.first.wpilibj.Encoder;
+import edu.wpi.first.wpilibj.Joystick;
+import edu.wpi.first.wpilibj.TimedRobot;
+import edu.wpi.first.wpilibj.Ultrasonic;
+import edu.wpi.first.wpilibj.event.BooleanEvent;
+import edu.wpi.first.wpilibj.event.EventLoop;
+import edu.wpi.first.wpilibj.motorcontrol.MotorController;
+import edu.wpi.first.wpilibj.motorcontrol.PWMSparkMax;
+
+public class Robot extends TimedRobot {
+  public static final int SHOT_VELOCITY = 200; // rpm
+  public static final int TOLERANCE = 8; // rpm
+  public static final int KICKER_THRESHOLD = 15; // mm
+
+  private final MotorController m_shooter = new PWMSparkMax(0);
+  private final Encoder m_shooterEncoder = new Encoder(0, 1);
+  private final PIDController m_controller = new PIDController(0.3, 0, 0);
+  private final SimpleMotorFeedforward m_ff = new SimpleMotorFeedforward(0.1, 0.065);
+
+  private final MotorController m_kicker = new PWMSparkMax(1);
+  private final Ultrasonic m_kickerSensor = new Ultrasonic(2, 3);
+
+  private final MotorController m_intake = new PWMSparkMax(2);
+
+  private final EventLoop m_loop = new EventLoop();
+  private final Joystick m_joystick = new Joystick(0);
+
+  @Override
+  public void robotInit() {
+    m_controller.setTolerance(TOLERANCE);
+
+    BooleanEvent isBallAtKicker =
+        new BooleanEvent(m_loop, () -> m_kickerSensor.getRangeMM() < KICKER_THRESHOLD);
+    BooleanEvent intakeButton = new BooleanEvent(m_loop, () -> m_joystick.getRawButton(2));
+
+    // if the thumb button is held
+    intakeButton
+        // and there is not a ball at the kicker
+        .and(isBallAtKicker.negate())
+        // activate the intake
+        .ifHigh(() -> m_intake.set(0.5));
+
+    // if the thumb button is not held
+    intakeButton
+        // or there is a ball in the kicker
+        .or(isBallAtKicker)
+        // stop the intake
+        .ifHigh(m_intake::stopMotor);
+
+    BooleanEvent shootTrigger = new BooleanEvent(m_loop, m_joystick::getTrigger);
+
+    // if the trigger is held
+    shootTrigger
+        // accelerate the shooter wheel
+        .ifHigh(
+        () ->
+            m_shooter.setVoltage(
+                m_controller.calculate(m_shooterEncoder.getRate(), SHOT_VELOCITY)
+                    + m_ff.calculate(SHOT_VELOCITY)));
+    // if not, stop
+    shootTrigger.ifHigh(m_shooter::stopMotor);
+
+    BooleanEvent atTargetVelocity =
+        new BooleanEvent(m_loop, m_controller::atSetpoint)
+            // debounce for more stability
+            .debounce(0.2);
+
+    // if we're at the target velocity, kick the ball into the shooter wheel
+    atTargetVelocity.ifHigh(() -> m_kicker.set(0.7));
+
+    // when we stop being at the target velocity, it means the ball was shot
+    atTargetVelocity
+        .falling()
+        // so stop the kicker
+        .ifHigh(m_kicker::stopMotor);
+  }
+
+  @Override
+  public void robotPeriodic() {
+    // poll all the bindings
+    m_loop.poll();
+  }
+}

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

@@ -89,6 +89,17 @@
     "mainclass": "Main",
     "commandversion": 2
   },
+  {
+    "name": "EventLoop",
+    "description": "Demonstrate managing a ball system using EventLoop and BooleanEvent.",
+    "tags": [
+      "EventLoop"
+    ],
+    "foldername": "eventloop",
+    "gradlebase": "java",
+    "mainclass": "Main",
+    "commandversion": 2
+  },
   {
     "name": "Relay",
     "description": "Demonstrate controlling a Relay from Joystick buttons.",