Arduino/ESP library to simplify working with buttons.

• Author: Lennart Hennigs (https://www.lennarthennigs.de)
• Copyright (C) 2017-2024 Lennart Hennigs.
• Released under the MIT license.

This library allows you to use callback functions to track single, double, triple and long clicks. Alternatively, it provides function to use in your main loop(). The library also takes care of debouncing. Using this lib will reduce and simplify your source code significantly.

It has been tested with Arduino, ESP8266 and ESP32 devices.

To see the latest changes to the library please take a look at the Changelog.

If you find this library helpful please consider giving it a ⭐️ at GitHub and/or buy me a ☕️.

Thank you!

This library allows you to define a button and uses callback functions to detect different types of button interactions. If you don't want to use callback there are also functions available for using it in your code's main loop().

• Include the library on top

 #include "Button2.h"

• Define the button either using the constructor or the begin() function.

  void begin(byte attachTo, byte buttonMode = INPUT_PULLUP, boolean activeLow  = true);

• You can use the class for "real" buttons (pullup, pulldown, and active low).
• Per default the button pins are defined as INPUT_PULLUP. You can override this upon creation.

   #include "Button2.h"
   #define BUTTON_PIN D3

   Button2 button;

   void setup() {
     button.begin(BUTTON_PIN);
  }

• You can also the library with other types of buttons, e.g. capacitive touch or ones handled via I2C. See the section on defining custom handlers below.

• Instead of frequently checking the button state in your main loop() this class allows you to assign callback functions.

• You can define callback functions to track various types of clicks:

  • setTapHandler() will be be called when any click occurs. This is the most basic handler. It ignores all timings built-in the library for double or triple click detection.
  • setClickHandler() will be triggered after a single click occurred.
  • setChangedHandler(), setPressedHandler() and setReleasedHandler() allow to detect basic interactions.
  • setLongClickDetectedHandler() will be triggered as soon as the long click timeout has passed.
  • setLongClickHandler() will be triggered after the button has released.
  • setDoubleClickHandler() and setTripleClickHandler() detect complex interactions.

• Note: You will experience a short delay with setClickHandler() and setLongClickHandler() as need to check whether a long or multi-click is in progress. For immediate feedback use setTapHandler()or setLongClickDetectedHandler()

• You can assign callback functions for single or for multiple buttons.

• You can track individual or multiple events with a single handler.

• Please take a look at the included examples (see below) to get an overview over the different callback handlers and their usage.

• All callback functions need a Button2 reference parameter. There the reference to the triggered button is stored. This can used to call status functions, e.g. wasPressedFor().

• There are two possible callback functions: setLongClickDetectedHandler() and setLongClickHandler().
• setLongClickDetectedHandler() will be called as soon as the defined timeout has passed.
• setLongClickHandler() will only be called after the button has been released.
• setLongClickDetectedRetriggerable(bool retriggerable) allows you to define whether want to get multiple notifications for a single long click depending on the timeout.
• getLongClickCount() gets you the number of long clicks – this is useful when retriggerable is set.

• For the class to work, you need to call the button's loop() member function in your sketch's loop() function.

   #include "Button2.h"
   #define BUTTON_PIN D3

   Button2 button;

   void handleTap(Button2& b) {
    // check for really long clicks
    if (b.wasPressedFor() > 1000) {
    // do something
    }
   }

   void setup() {
     button.begin(BUTTON_PIN);
     button.setTapHandler(handleTap);
  }

  void loop() {
     button.loop();
  }

• As the loop()function needs to be called continuously, delay() and other blocking functions will interfere with the detection of clicks. Consider cleaning up your loop or call the loop() function via an interrupt.
• Please see the examples below for more details.

• Alternatively, you can call the button's loop() function via a timer interrupt.
• I haven't tried this extensively, USE THIS AT YOUR OWN RISK!
• You need make sure that the interval is quick enough that it can detect your timeouts (see below).
• There is an example for the ESP32 ESP32TimerInterrupt.ino that I tested.

• The default timeouts for events are (in ms):

  #define BTN_DEBOUNCE_MS 50
  #define BTN_LONGCLICK_MS 200
  #define BTN_DOUBLECLICK_MS 300

• You can define your own timeouts by using these setter functions:
  • void setDebounceTime(unsigned int ms)
  • void setLongClickTime(unsigned int ms)
  • void setDoubleClickTime(unsigned int ms)
• There are also getter functions available, if needed.

• Even though I suggest to use handlers for tracking events, you can also use Button2 to check button's state in the main loop
• bool wasPressed() allows you to check whether the button was pressed
• clickType read(bool keepState = false) gives you the type of click that took place
• clickType wait(bool keepState = false) combines read() and wasPressed() and halts execution until a button click was detected. Thus, it is blocking code.
• The clickType is an enum defined as...

    enum clickType {
      single_click, 
      double_click, 
      triple_click, 
      long_click,
      empty
    };

• There are also dedicated waits (waitForClick(), waitForDouble(), waitForTriple() and waitForLong()) to detect a specific type
• The read() and the wait functions will reset the state of wasPressed() unless specified otherwise (via a bool parameter)
• resetPressedState() allows you to clear value returned by wasPressed() – it is similar to passing keepState = false for read() or wait().
• Check out the ButtonLoop.ino example to see it in action

• There are several status functions available to check the status of a button:

unsigned int wasPressedFor() const;
byte getNumberOfClicks() const;
byte getType() const;
boolean isPressed() const;
boolean isPressedRaw() const;
bool wasPressed() const;

• Each button instance gets a unique (auto incremented) ID upon creation.
• You can get a buttons' ID via getID().
• Alternatively, you can use setID(int newID) to set a new one. But then you need to make sure that they are unique.

• Out of the box Button2 supports regular hardware buttons.
• If you want to add other button types you need to define your own function that tracks the state of the button.
• Use setButtonStateFunction() to assign it to your Button2 instance
• Make the button pin 'VIRTUAL', i.e. by calling button.begin(VIRTUAL_PIN);
• And don't forget to initialize the button as this cannot be handled by Button2
• See ESP32CapacitiveTouch.ino, M5StackCore2CustomHandler.ino, and CustomButtonStateHandler.ino as examples.

• SingleButtonSimple.ino – the most basic example, shows how to assign event handlers
• LongpressHandler.ino – shows how determine the time of a button press
• SingleButton.ino – shows the different event handlers
• MultipleButtons.ino – how to use two buttons
• MultiHandler.ino – how to use a single handler for multiple events
• MultiHandlerTwoButtons.ino – a single handler for multiple buttons
• TrackDualButtonClick.ino – how to detect when two buttons are clicked at the same time
• CustomButtonStateHandler.ino - how to assign your own button handler
• ESP32CapacitiveTouch.ino – how to access the ESP32s capacitive touch handlers
• M5StackCore2CustomHandler.ino - example for the M5Stack Core2 touch buttons
• ESP32TimerInterrupt.ino - how to use a timer interrupt with the library.
• ButtonLoop.ino – how to use the button class in the main loop (I recommend using handlers, but well...)

The button class offers a few additional functions, please take a look at the Class Definition below.

See below the constructors and member functions the library provides:

Button2();
Button2(byte attachTo, byte buttonMode = INPUT_PULLUP, boolean activeLow = true);

void begin(byte attachTo, byte buttonMode = INPUT_PULLUP, boolean activeLow  = true);

void setDebounceTime(unsigned int ms);
void setLongClickTime(unsigned int ms);
void setDoubleClickTime(unsigned int ms);

unsigned int getDebounceTime();
unsigned int getLongClickTime();
unsigned int getDoubleClickTime();
byte getPin();

void reset();

void setButtonStateFunction(StateCallbackFunction f);

void setChangedHandler(CallbackFunction f);
void setPressedHandler(CallbackFunction f);
void setReleasedHandler(CallbackFunction f);

void setTapHandler(CallbackFunction f);
void setClickHandler(CallbackFunction f);
void setDoubleClickHandler(CallbackFunction f);
void setTripleClickHandler(CallbackFunction f);

void setLongClickHandler(CallbackFunction f);
void setLongClickDetectedHandler(CallbackFunction f);
void setLongClickDetectedRetriggerable(bool retriggerable);
void byte getLongClickCount() const;

unsigned int wasPressedFor() const;
void resetPressedState();
boolean isPressed() const;
boolean isPressedRaw() const;

bool wasPressed() const;
clickType read(bool keepState = false);
clickType wait(bool keepState = false);
void waitForClick(bool keepState = false);
void waitForDouble(bool keepState = false);
void waitForTriple(bool keepState = false);
void waitForLong(bool keepState = false);

byte getNumberOfClicks() const;
byte getType() const;
String clickToString(clickType type) const;

int getID() const;
void setID(int newID);

bool operator == (Button2 &rhs);

void loop();

Open the Arduino IDE choose "Sketch > Include Library" and search for "Button2". Or download the ZIP archive (https://github.com/lennarthennigs/Button2/zipball/master), and choose "Sketch > Include Library > Add .ZIP Library..." and select the downloaded file.

MIT License

Copyright (c) 2017-2023 Lennart Hennigs

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.

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