Bounce2
BOUNCE 2

Debouncing library for Arduino and Wiring by Thomas Ouellet Fredericks with many contributions from the community : https://github.com/thomasfredericks/Bounce2/graphs/contributors

Basically, 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. More about debouncing:

See the bottom of this page for a basic usage example and the "examples" folder for more.

The library is composed of three classes:

  • Debouncer : The code that does the actual debouncing. Only advanced users should play with this class.
  • Bounce : This is the general use library. It links the Debouncer to a hardware pin on your board.
  • Button : A special version of Bounce for buttons that are pressed.

INSTALLATION & DOWNLOAD

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

INSTANTIATE

#include <Bounce2.h>
Bounce b = Bounce(); // Instantiate a Bounce object

SETUP

b.attach ( <PIN> , <PIN MODE> );
b.interval( <INTERVAL IN MS> );

LOOP

b.update();
if ( b.changed() ) {
// THE STATE OF THE INPUT CHANGED
int deboucedValue = b.read();
// DO SOMETHING WITH THE VALUE
}

BOUNCE EXAMPLE

// This example toggles the debug LED (pin 13) on or off when a button on pin 2 is pressed.
// Include the Bounce2 library found here :
// https://github.com/thomasfredericks/Bounce2
#include <Bounce2.h>
#define BUTTON_PIN 2
#define LED_PIN 13
int ledState = LOW;
Bounce b = Bounce(); // Instantiate a Bounce object
void setup() {
b.attach(BUTTON_PIN,INPUT_PULLUP); // Attach the debouncer to a pin with INPUT_PULLUP mode
b.interval(25); // Use a debounce interval of 25 milliseconds
pinMode(LED_PIN,OUTPUT); // Setup the LED
digitalWrite(LED_PIN,ledState); // Turn off the LED
}
void loop() {
b.update(); // Update the Bounce instance
if ( b.fell() ) { // Call code if button transitions from HIGH to LOW
ledState = !ledState; // Toggle LED state
digitalWrite(LED_PIN,ledState); // Apply new LED state
}
}

BUTTON EXAMPLE

/*
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
// 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);
}
}

DOCUMENTATION

The complete class documentation can be found in the "docs" folder or online here.

GITHUB PAGE (SOURCE CODE)

https://github.com/thomasfredericks/Bounce2

HAVE A QUESTION?

Please post your questions here.

ALTERNATE DEBOUNCE ALGORITHMS FOR ADVANCED USERS AND 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" (or in your code before including "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

WITH PROMPT DETECTION

By defining "#define BOUNCE_WITH_PROMPT_DETECTION" in "Bounce.h" (or in your code before including "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
Bounce2::Button
Definition: Bounce2.h:258
Debouncer::interval
void interval(uint16_t interval_millis)
Sets the debounce interval in milliseconds.
Definition: Bounce2.cpp:14
Bounce2::Button::pressed
bool pressed() const
Returns true if the button was physically pressed
Definition: Bounce2.h:302
Debouncer::update
bool update()
Updates the pin's state.
Definition: Bounce2.cpp:32
Bounce
The Debouncer:Bounce class. Links the Deboucing class to a hardware pin. This class is odly named,...
Definition: Bounce2.h:168
Bounce2::Button::setPressedState
void setPressedState(bool state)
Set the electrical state (HIGH/LOW) that corresponds to a physical press. By default,...
Definition: Bounce2.h:281
Debouncer::fell
bool fell() const
Returns true if pin signal transitions from high to low.
Definition: Bounce2.cpp:128
Bounce::attach
void attach(int pin, int mode)
Attach to a pin and sets that pin's mode (INPUT, INPUT_PULLUP or OUTPUT).
Definition: Bounce2.cpp:149
Debouncer::read
bool read() const
Returns the pin's state (HIGH or LOW).
Definition: Bounce2.cpp:118
Debouncer::changed
bool changed() const
Returns true if the state changed on last update.
Definition: Bounce2.h:130