Bounce2

Debouncing library for Arduino and Wiring by Thomas Ouellet Fredericks and many contributors.

The mechanical part of buttons and switches vibrate slightly when closed or opened causing multiple undesired false states (similar to noise). This library filters out these undesired state changes. You can learn more about debouncing here:

• John Errington's Experiments with an Arduino - Using digital inputs: Switch bounce and solutions to it
• Wikipedia article on contact Debouncing

The library is composed of three classes:

• Bounce2::Button : The class that most people will use. It is the most feature rich class for deboucing hardware buttons.
• Debouncer : The code that does the actual debouncing. Only advanced users should use this class for creating their own implememtations.
• Bounce : This class links the Debouncer class to a hardware pin on your board. It is odly named because it needs to be backward compatible to previous versions of this library.

Need Help?

Please post your usage questions on the Arduino Forums.

Installation

Install through your software's Library Manager or download the latest version here and put the "Bounce2" folder in your "libraries" folder.

Please note that the original version of this library (Bounce 1) is included in the "extras" folder of the download but not supported anymore.

Basic Use

Global Space

#include <Bounce2.h> 
Bounce2::Button button = Bounce2::Button(); // INSTANTIATE A Bounce2::Button OBJECT

Configuration in setup()

In the code sample below :

• Change PIN to the hardware pin of the button.
• Change PIN_MODE to INPUT_PULLUP if using an internal pullup, or INPUT if using an external pullup.
• Change INTERVAL_IN_MS to the debounce interval in millisecons. 5 is a good value.
• Change PRESSED_STATE to LOW if the button outputs a LOW when pressed, or to HIGH if the button outputs a HIGH when pressed.

button.attach ( PIN , PIN_MODE );
button.interval( INTERVAL_IN_MS );
button.setPressedState( PRESSED_STATE ); 

Use in loop()

// UPDATE THE BUTTON BY CALLING .update() AT THE BEGINNING OF THE LOOP:
button.update();

// IF THE BUTTON WAS PRESSED THIS LOOP:
if ( button.pressed() ) {
    // DO SOMETHING IF THE BUTTON WAS PRESSED THIS LOOP...
}

Examples

A Button Toggling a LED

/* 
 DESCRIPTION
 ====================
 This is an example of the Bounce2::Button class. 
 When the user presses a physical button, it toggles a LED on or off.
 The Button class matches an electrical state to a physical action. 
 Use .setPressedState(LOW or HIGH) to set the detection state for when the button is pressed.

 INSTRUCTIONS
 ====================
 Set BUTTON_PIN to the pin attached to the button.
 Set LED_PIN to the pin attached to a LED.
 
 */
 
// Include the Bounce2 library found here :
// https://github.com/thomasfredericks/Bounce2
#include <Bounce2.h>

// INSTANTIATE A Button OBJECT
Bounce2::Button button = Bounce2::Button();

// WE WILL attach() THE BUTTON TO THE FOLLOWING PIN IN setup()
#define BUTTON_PIN 39 

// DEFINE THE PIN FOR THE LED :
// 1) SOME BOARDS HAVE A DEFAULT LED (LED_BUILTIN)
//#define LED_PIN LED_BUILTIN
// 2) OTHERWISE SET YOUR OWN PIN
#define LED_PIN 13

// SET A VARIABLE TO STORE THE LED STATE
bool ledState = LOW;

void setup() {

  // BUTTON SETUP 
  
  // SELECT ONE OF THE FOLLOWING :
  // 1) IF YOUR BUTTON HAS AN INTERNAL PULL-UP
  // button.attach( BUTTON_PIN ,  INPUT_PULLUP ); // USE INTERNAL PULL-UP
  // 2) IF YOUR BUTTON USES AN EXTERNAL PULL-UP
  button.attach( BUTTON_PIN, INPUT ); // USE EXTERNAL PULL-UP

  // DEBOUNCE INTERVAL IN MILLISECONDS
  button.interval(5); 

  // INDICATE THAT THE LOW STATE CORRESPONDS TO PHYSICALLY PRESSING THE BUTTON
  button.setPressedState(LOW); 
  
  // LED SETUP
  pinMode(LED_PIN,OUTPUT);
  digitalWrite(LED_PIN,ledState);

}

void loop() {
  // UPDATE THE BUTTON
  // YOU MUST CALL THIS EVERY LOOP
  button.update();

  if ( button.pressed() ) {
    
    // TOGGLE THE LED STATE : 
    ledState = !ledState; // SET ledState TO THE OPPOSITE OF ledState
    digitalWrite(LED_PIN,ledState);

  }
}

More Examples

You can find more examples in the examples folder.

Documentation

Bounce2::Button

The Bounce2::Button class extends Bounce and adds pressed() and released() methods. It is the most feature rich class of the library.

Method	Description
Button()	Create an instance of the Button class. By default, the pressed state is matched to a HIGH electrical level.
void update()	Updates the pin's state. Because Bounce does not use interrupts, you have to "update" the object before reading its value and it has to be done as often as possible (that means to include it in your loop()). Only call update() for each Bounce instance once per loop().
void setPressedState(bool state)	Set the electrical state (HIGH/LOW) that corresponds to a physical press. By default, the pressed state is matched to a HIGH electrical level.
bool getPressedState()	Get the electrical state (HIGH/LOW) that corresponds to a physical press.
bool isPressed()	Returns true if the button is currently pressed.
bool pressed()	Returns true if the button was pressed
bool released()	Returns true if the button was released
void attach(int pin, int mode)	Attach to a pin and sets that pin's mode (INPUT, INPUT_PULLUP or OUTPUT).
int getPin()	Return pin that this instance is attached to.
void interval ( uint16_t interval_millis )	Sets the debounce interval in milliseconds.
unsigned long previousDuration()	Returns the duration in milliseconds of the previous state.
unsigned long currentDuration()	Returns the duration in milliseconds of the current state. Is reset to 0 when the state changes.
bool changed()	Returns true if the state changed on last update.
bool read()	Returns the pin's state (HIGH or LOW).
bool fell()	Returns true if pin signal transitions from high to low since the last update.
bool rose()	Returns true if pin signal transitions from low to high since the last update.

Bounce

The Bounce class extends Debouncer and links it to a hardware pin. This class is odly named, but it will be kept that so it stays compatible with previous code.

Method	Description
Bounce()	Create an instance of the Bounce class.
void update()	Updates the pin's state. Because Bounce does not use interrupts, you have to "update" the object before reading its value and it has to be done as often as possible (that means to include it in your loop()). Only call update() for each Bounce instance once per loop().
void attach(int pin, int mode)	Attach to a pin and sets that pin's mode (INPUT, INPUT_PULLUP or OUTPUT).
int getPin()	Return pin that this instance is attached to.
void interval ( uint16_t interval_millis )	Sets the debounce interval in milliseconds.
unsigned long previousDuration()	Returns the duration in milliseconds of the previous state.
unsigned long currentDuration()	Returns the duration in milliseconds of the current state. Is reset to 0 when the state changes.
bool changed()	Returns true if the state changed on last update.
bool read()	Returns the pin's state (HIGH or LOW).
bool fell()	Returns true if pin signal transitions from high to low since the last update.
bool rose()	Returns true if pin signal transitions from low to high since the last update.

Debouncer

The Debouncer class. Just the debouncing code separated from all hardware.

Method	Description
Debouncer()	Create an instance of the Debouncer class.
void update()	Updates the pin's state. Because Bounce does not use interrupts, you have to "update" the object before reading its value and it has to be done as often as possible (that means to include it in your loop()). Only call update() for each Bounce instance once per loop().
void interval ( uint16_t interval_millis )	Sets the debounce interval in milliseconds.
unsigned long previousDuration()	Returns the duration in milliseconds of the previous state.
unsigned long currentDuration()	Returns the duration in milliseconds of the current state. Is reset to 0 when the state changes.
bool changed()	Returns true if the state changed on last update.
bool read()	Returns the pin's state (HIGH or LOW).
bool fell()	Returns true if pin signal transitions from high to low since the last update.
bool rose()	Returns true if pin signal transitions from low to high since the last update.

Alternate Algorithms

The following alternate debouncing algorithms are for advanced users or specific cases.

Stable Interval

By default, the Bounce library uses a stable interval to process the debouncing. This is simpler to understand and can cancel unwanted noise.

Lock-out Interval

By defining "#define BOUNCE_LOCK_OUT" in "Bounce.h" you can activate an alternative debouncing method. This method is a lot more responsive, but does not cancel noise.

#define BOUNCE_LOCK_OUT

Prompt Detection

By defining "#define BOUNCE_WITH_PROMPT_DETECTION" in "Bounce.h" you can activate an alternative debouncing method. Button state changes are available immediately so long as the previous state has been stable for the timeout period. Otherwise the state will be updated as soon as the timeout period allows.

• Able to report acurate switch time normally with no delay.
• Use when accurate switch transition timing is important.

#define BOUNCE_WITH_PROMPT_DETECTION