SwitchControl.h

/** @file
 *  Definition of the SWitchControl class. This file contains the definition of
 *  the class used to control, and detect button presses from, an illuminated
 *  push-button switch.
 *
 * @author Chris Page <chris@starforge.co.uk>
 * @copyright MIT License, 2020 Chris Page
 */
/* The MIT License (MIT)
 *
 * Copyright (c) 2020 Chris Page
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#ifndef SwitchControl_H
#define SwitchControl_H

#include <Arduino.h>

/** A class to interact with a SPST momentary illuminated switch. This class
 *  provides features to turn on or off the LED illumination in the switch,
 *  and software debounce and press/longpress detection for button pushes.
 *  This class requires one digital input pin and one digital output pin per
 *  instance, and allows the debounce and longpress timers to be configured
 *  during creation.
 */
class SwitchControl
{
public:
    /** The possible kinds of events that may be reported by update()
     */
    enum Event {
        EVENT_NONE,      //!< Nothing happened. Nothing to see here, move along.
        EVENT_PRESSED,   //!< The switch was pressed.
        EVENT_LONGPRESS, //!< The switch had been held long enough to trigger a longpress.
        EVENT_RELEASED   //!< The switch was released.
    };

    /** Create a new SwitchControl object for interacting with an illuminated
     *  push-button switch.
     *
     * @param switch_pin The digital pin the switch is connected to. This should
     *                   go high when the switch is pressed, and low when not.
     * @param led_pin    The digital pin the LED is connected to. The LED will be
     *                   initialised to be off during setup.
     * @param debounce_time Time in milliseconds to delay swith state change by to
     *                   allow for switch bounce to be ignored. Increase this if
     *                   spurious press and release events are generated.
     * @param longpress_time If the switch is held pressed for this amount of time
     *                   in milliseconds a 'long press' event will be generated.
     */
    SwitchControl(uint8_t switch_pin, uint8_t led_pin, unsigned long debounce_time = 50, unsigned long longpress_time = 3000) :
        switch_pin(switch_pin), led_pin(led_pin),
        switch_state(LOW),in_longpress(false),last_press(0),last_release(0),
        last_state(LOW),last_debounce(0),
        debounce_time(debounce_time), longpress_time(longpress_time)
    { /* fnord */ }


    /* ------------------------------------------------------------------------
     *  Setup and main loop interaction
     */

    /** Initialise the IO for the SWitchControl object.
     *  This sets the configuration of the IO pins for the switch and LED control,
     *  it should be called once from the global setup() function.
     */
    void setup();


    /** Check the status of the switch, and determine whether any events
     *  should be triggered as a result of its state. This performs switch
     *  debouncing to try to avoid spurious events, and can detect when the switch
     *  has been held down to trigger a long press event.
     *
     * @return A value indicating whether an event happened during this
     *         update, and if so what kind of event.
     */
    Event update();

    /* ------------------------------------------------------------------------
     *  Control functions
     */

    /** Set the illumination LED in the switch to either on or off.
     *
     * @param state Set to `true` to turn the LED on, `false` to turn it off.
     */
    void set_led_state(bool state);


    /* ------------------------------------------------------------------------
     *  State lookup
     */

    /** Determine whether the switch is currently pressed.
     *
     * @return `true` if the switch is currently pressed, `false` if it is not.
     */
    bool is_pressed()
    {
        return (switch_state == HIGH);
    }


    /** Obtain the time since the last press event happened. Note that this
     *  will return a value since the press event even if the switch has been
     *  released.
     *
     * @return The time in milliseconds since the last press event.
     */
    unsigned long time_since_pressed()
    {
        return (millis() - last_press);
    }


    /** Obtain the time since the last release event happened. This will return
     *  a value even if the switch has been pressed.
     *
     * @return The time in milliseconds since the last release event.
     */
    unsigned long time_since_released()
    {
        return (millis() - last_release);
    }

private:
    // Digital pin configuration
    uint8_t switch_pin;           //!< The digital pin the switch connected to
    uint8_t led_pin;              //!< The digital pin the indicator LED connected to

    // Button state information
    uint8_t switch_state;         //!< The current switch state
    bool in_longpress;            //!< Are we in a long press state?
    unsigned long last_press;     //!< The time in millis since last reset that the last press happened (after debounce)
    unsigned long last_release;   //!< The time in millis since last reset that the last release happened (after debounce)

    // Timing control
    unsigned long debounce_time;  //!< Time to delay during debounce, in milliseconds.
    unsigned long longpress_time; //!< How long the switch must be held to trigger a 'longpress' event

    // State variables needed to persist data over update()s
    uint8_t last_state;           //!< Previous reading from the switch
    unsigned long last_debounce;  //!< The time at which the last state change occurred during debounce
};

#endif