[wpilib] Add EventLoop (#4104)

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

wpilibcExamples/src/main/cpp/examples/EventLoop/cpp/Robot.cpp

@@ -0,0 +1,102 @@
+// 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 <frc/Encoder.h>
+#include <frc/Joystick.h>
+#include <frc/TimedRobot.h>
+#include <frc/Ultrasonic.h>
+#include <frc/controller/PIDController.h>
+#include <frc/controller/SimpleMotorFeedforward.h>
+#include <frc/event/BooleanEvent.h>
+#include <frc/event/EventLoop.h>
+#include <frc/motorcontrol/PWMSparkMax.h>
+#include <units/angular_velocity.h>
+#include <units/length.h>
+#include <units/time.h>
+#include <units/voltage.h>
+
+static const auto SHOT_VELOCITY = 200_rpm;
+static const auto TOLERANCE = 8_rpm;
+static const auto KICKER_THRESHOLD = 15_mm;
+
+class Robot : public frc::TimedRobot {
+ public:
+  void RobotInit() override {
+    m_controller.SetTolerance(TOLERANCE.value());
+
+    frc::BooleanEvent isBallAtKicker{&m_loop, [&kickerSensor = m_kickerSensor] {
+                                       return kickerSensor.GetRange() <
+                                              KICKER_THRESHOLD;
+                                     }};
+    frc::BooleanEvent intakeButton{
+        &m_loop, [&joystick = m_joystick] { return joystick.GetRawButton(2); }};
+
+    // if the thumb button is held
+    (intakeButton
+     // and there is not a ball at the kicker
+     && !isBallAtKicker)
+        // activate the intake
+        .IfHigh([&intake = m_intake] { intake.Set(0.5); });
+
+    // if the thumb button is not held
+    (intakeButton
+     // or there is a ball in the kicker
+     || isBallAtKicker)
+        // stop the intake
+        .IfHigh([&intake = m_intake] { intake.Set(0.0); });
+
+    frc::BooleanEvent shootTrigger{
+        &m_loop, [&joystick = m_joystick] { return joystick.GetTrigger(); }};
+
+    // if the trigger is held
+    shootTrigger
+        // accelerate the shooter wheel
+        .IfHigh([&shooter = m_shooter, &controller = m_controller, &ff = m_ff,
+                 &encoder = m_shooterEncoder] {
+          shooter.SetVoltage(units::volt_t(controller.Calculate(
+                                 encoder.GetRate(), SHOT_VELOCITY.value())) +
+                             ff.Calculate(SHOT_VELOCITY));
+        });
+    // if not, stop
+    shootTrigger.IfHigh([&shooter = m_shooter] { shooter.Set(0.0); });
+
+    frc::BooleanEvent atTargetVelocity =
+        frc::BooleanEvent(
+            &m_loop,
+            [&controller = m_controller] { return controller.AtSetpoint(); })
+            // debounce for more stability
+            .Debounce(0.2_s);
+
+    // if we're at the target velocity, kick the ball into the shooter wheel
+    atTargetVelocity.IfHigh([&kicker = m_kicker] { 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([&kicker = m_kicker] { kicker.Set(0.0); });
+  }
+
+  void RobotPeriodic() override { m_loop.Poll(); }
+
+ private:
+  frc::PWMSparkMax m_shooter{0};
+  frc::Encoder m_shooterEncoder{0, 1};
+  frc::PIDController m_controller{0.3, 0, 0};
+  frc::SimpleMotorFeedforward<units::radians> m_ff{0.1_V, 0.065_V / 1_rpm};
+
+  frc::PWMSparkMax m_kicker{1};
+  frc::Ultrasonic m_kickerSensor{2, 3};
+
+  frc::PWMSparkMax m_intake{3};
+
+  frc::EventLoop m_loop{};
+  frc::Joystick m_joystick{0};
+};
+
+#ifndef RUNNING_FRC_TESTS
+int main() {
+  return frc::StartRobot<Robot>();
+}
+#endif

wpilibcExamples/src/main/cpp/examples/examples.json

@@ -84,6 +84,16 @@
     "gradlebase": "cpp",
     "commandversion": 2
   },
+  {
+    "name": "EventLoop",
+    "description": "Demonstrate managing a ball system using EventLoop and BooleanEvent.",
+    "tags": [
+      "EventLoop"
+    ],
+    "foldername": "EventLoop",
+    "gradlebase": "cpp",
+    "commandversion": 2
+  },
   {
     "name": "Arcade Drive",
     "description": "An example program which demonstrates the use of Arcade Drive with the DifferentialDrive class",