Last Updated:15/09/2021

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How To 1 - Debouncing Buttons

Lessons >> How To >> How To 1 - Debouncing Buttons

Lesson Contents

Issues without debouncing
Simple debounce example
Debouncing in a function

All examples have two buttons but can easily be explanded for more buttons as required


Circuit

2 x push buttons

2 x 10k Ohm resistors

Digital pin and resistor to Gnd are on one side of the button
5v connection to opposite side of the button

Example 1: debounceNoDebounce.ino

Simple sketch showing the issues of using buttons without debouncing

Click to Download code:debounceNoDebounce.ino

 

 
/* debounceNoDebounce

   2 buttons without debounce
   This script shows the impact of button bounce in different situations. 

*/
//Global variables
//set up pins 8 & 9 with buttons
const int buttonPin1 = 8;
const int buttonPin2 = 9;
//built in led
const int ledPin = 13;


void setup() {
  Serial.begin(9600);
  Serial.println("debounceNoDebounce");
  pinMode(buttonPin1, INPUT);
  pinMode(buttonPin2, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  //local variable
  int Pressed;
  
  Pressed = digitalRead(buttonPin1);
  //With an LED being turned on or off, if the button bounces the same signal to turn it on is repeated
  //However to the user there are no implications
  if (Pressed > 0) {//Code to do something when button 1 pressed goes in here
    digitalWrite(ledPin,HIGH);
  }else{
    digitalWrite(ledPin,LOW);  
  }
  Pressed = digitalRead(buttonPin2);
  //With button 2 we see the impact in multiple Serial.println() taking place
  if (Pressed > 0) {//Code to do something when button 2 pressed goes in here
    Serial.println("Button 2 Pressed");
    Serial.println(millis());
  }


}

Example 2: debounceV1.ino

Debounced buttons example

Click to Download code:debounceV1.ino

 

 
/* debounceV1

   How to debounce buttons
  see http://www.digitaltown.co.uk/lesson7delaymillis.php for more information on millis() timers
*/

const int buttonPin1 = 8;
const int buttonPin2 = 9;
// 
unsigned long buttonDebounce;
int buttonDebounceSensitivity = 220;//to high and system becomes unresponsive, too low and multiple presses recorded


void setup() {
  Serial.begin(9600);
  Serial.println("debounceV1");
  pinMode(buttonPin1, INPUT);
  pinMode(buttonPin2, INPUT);
}

void loop() {
  int Pressed;
  if (millis() > buttonDebounce) {
    buttonDebounce = millis() + buttonDebounceSensitivity;
    Pressed = digitalRead(buttonPin1);
    if (Pressed > 0) {//Code to do something when button 1 pressed goes in here
      Serial.println("Button 1 Pressed");
      Serial.println(millis());
    }
    Pressed = digitalRead(buttonPin2);
    if (Pressed > 0) {//Code to do something when button 2 pressed goes in here
      Serial.println("Button 2 Pressed");
      Serial.println(millis());
    }
  }

}

Example 3: debounceV2.ino

Button processing and debounce moved into a function

Click to Download code:debounceV2.ino

 

 
/* debounceV2

   Buttons and debounce in a function
  see http://www.digitaltown.co.uk/lesson7delaymillis.php for more information on millis() timers
*/

const int buttonPin1 = 8;
const int buttonPin2 = 9;
const int ledPin = 13;
unsigned long buttonDebounce;
int buttonDebounceSensitivity = 220;//to high and system becomes unresponsive, too low and multiple presses recorded

void buttonPress(){
 int Pressed;
  if (millis() > buttonDebounce) {
    buttonDebounce = millis() + buttonDebounceSensitivity;
    Pressed = digitalRead(buttonPin1);
    if (Pressed > 0) {//Code to do something when button 1 pressed goes in here
      Serial.println("Button 1 Pressed");//TX led will flash
      Serial.println(millis());
      digitalWrite(ledPin,HIGH);//Turn built in led on
    }else{
      digitalWrite(ledPin,LOW); //Turn built in led off 
    }
    Pressed = digitalRead(buttonPin2);
    if (Pressed > 0) {//Code to do something when button 2 pressed goes in here
      Serial.println("Button 2 Pressed");//TX led will flash
      Serial.println(millis());
    }
  } 
}

void setup() {
  Serial.begin(9600);
  Serial.println("debounceV2");
  pinMode(buttonPin1, INPUT);
  pinMode(buttonPin2, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  buttonPress(); 

}

Additional Resource Links

Don't forget to use the Reference in you Arduino IDE and look at the block comments and single line comments for more help on this lesson.

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