Debouncer.hpp

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// 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.
 
#pragma once
 
#include "wpi/units/time.hpp"
#include "wpi/util/SymbolExports.hpp"
 
namespace wpi::math {
/**
 * A simple debounce filter for boolean streams.  Requires that the boolean
 * change value from baseline for a specified period of time before the filtered
 * value changes.
 */
class WPILIB_DLLEXPORT Debouncer {
 public:
  /**
   * Type of debouncing to perform.
   */
  enum DebounceType {
    /// Rising edge.
    kRising,
    /// Falling edge.
    kFalling,
    /// Both rising and falling edges.
    kBoth
  };
 
  /**
   * Creates a new Debouncer.
   *
   * @param debounceTime The number of seconds the value must change from
   *                     baseline for the filtered value to change.
   * @param type         Which type of state change the debouncing will be
   *                     performed on.
   */
  explicit Debouncer(wpi::units::second_t debounceTime,
                     DebounceType type = DebounceType::kRising);
 
  /**
   * Applies the debouncer to the input stream.
   *
   * @param input The current value of the input stream.
   * @return The debounced value of the input stream.
   */
  bool Calculate(bool input);
 
  /**
   * Sets the time to debounce.
   *
   * @param time The number of seconds the value must change from baseline
   *             for the filtered value to change.
   */
  constexpr void SetDebounceTime(wpi::units::second_t time) {
    m_debounceTime = time;
  }
 
  /**
   * Gets the time to debounce.
   *
   * @return The number of seconds the value must change from baseline
   *             for the filtered value to change.
   */
  constexpr wpi::units::second_t GetDebounceTime() const {
    return m_debounceTime;
  }
 
  /**
   * Set the debounce type.
   *
   * @param type Which type of state change the debouncing will be performed on.
   */
  constexpr void SetDebounceType(DebounceType type) {
    m_debounceType = type;
 
    m_baseline = m_debounceType == DebounceType::kFalling;
  }
 
  /**
   * Get the debounce type.
   *
   * @return Which type of state change the debouncing will be performed on.
   */
  constexpr DebounceType GetDebounceType() const { return m_debounceType; }
 
 private:
  wpi::units::second_t m_debounceTime;
  bool m_baseline;
  DebounceType m_debounceType;
 
  wpi::units::second_t m_prevTime;
 
  void ResetTimer();
 
  bool HasElapsed() const;
};
}  // namespace wpi::math