Arduino Nano ESP32 - Button - Debounce

When a button is pressed/released or when a switch is toggled between ON and OFF, its state is changed from LOW to HIGH ( or HIGH to LOW) once. Is this correct?

⇒ No, it is not. That is because in the physical world. when you do a single press on a button, the state of the button is quickly toggled between LOW and HIGH several times rather than once. This is the mechanical and physical characteristic. This phenomenon is known with a name: chattering. The chattering phenomenon makes MCU (e.g. ESP32) read multiple button presses in response to a single actual press. This results in a malfunction. The process to eliminate this phenomenon is called debounce. This tutorial shows how to do it.

Arduino Nano ESP32 chattering phenomenon

This tutorial provides:

Hardware Preparation

1×Arduino Nano ESP32
1×USB Cable Type-C
1×Push Button
1×(Optional) Panel-mount Push Button
1×Breadboard
1×Jumper Wires
1×(Optional) DC Power Jack
1×(Recommended) Screw Terminal Adapter for Arduino Nano

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
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Overview of Button

We have specific tutorials about button. The tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, Arduino Nano ESP32 code... Learn more about them at the following links:

Wiring Diagram

The wiring diagram between Arduino Nano ESP32 and Button

This image is created using Fritzing. Click to enlarge image

To make it clear, let's run Arduino Nano ESP32 code WITHOUT and WITH debounce, and compare their results

Reading Button without Debounce

Detailed Instructions

To get started with Arduino Nano ESP32, follow these steps:

  • If you are new to Arduino Nano ESP32, refer to the tutorial on how to set up the environment for Arduino Nano ESP32 in the Arduino IDE.
  • Wire the components according to the provided diagram.
  • Connect the Arduino Nano ESP32 board to your computer using a USB cable.
  • Launch the Arduino IDE on your computer.
  • Select the Arduino Nano ESP32) board and its corresponding COM port.* Copy the below code and paste it to Arduino IDE.
/* * This Arduino Nano ESP32 code was developed by newbiely.com * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano-esp32/arduino-nano-esp32-button-debounce */ #define BUTTON_PIN D2 // Arduino Nano ESP32 pin D2 pin connected to button int prev_state = LOW; // The previous state from the input pin int button_state; // The current reading from the input pin void setup() { // Initialize the Serial to communicate with the Serial Monitor. Serial.begin(9600); // initialize the button pin as an pull-up input (HIGH when the switch is open and LOW when the switch is closed) pinMode(BUTTON_PIN, INPUT_PULLUP); } void loop() { // read the state of the switch/button: button_state = digitalRead(BUTTON_PIN); if (prev_state == HIGH && button_state == LOW) Serial.println("The button is pressed"); else if (prev_state == LOW && button_state == HIGH) Serial.println("The button is released"); // save the the last state prev_state = button_state; }
  • Compile and upload code to Arduino Nano ESP32 board by clicking Upload button on Arduino IDE
Arduino IDE Upload Code
  • Open Serial Monitor on Arduino IDE
How to open serial monitor on Arduino IDE
  • Press the button once but keep it several seconds, and then release it.
  • Check out the result on the Serial Monitor. It looks like the below:
COM6
Send
The button is pressed The button is pressed The button is pressed The button is released The button is released
Autoscroll Show timestamp
Clear output
9600 baud  
Newline  

⇒ As you can see, you did only a single press and release, but Arduino Nano ESP32 read multiple presses and releases.

※ NOTE THAT:

The chattering phenomenon does not happen all times. If it does not happen, please try the above test several time.

Reading Button with Debounce

Detailed Instructions

/* * This Arduino Nano ESP32 code was developed by newbiely.com * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano-esp32/arduino-nano-esp32-button-debounce */ #define BUTTON_PIN D2 // Arduino Nano ESP32 pin D2 pin connected to button #define DEBOUNCE_TIME 50 // The debounce time in millisecond, increase this time if it still chatters int prev_state_steady = LOW; // The previous steady state from the input pin int prev_state_flick = LOW; // The previous flickerable state from the input pin int button_state; // The current reading from the input pin unsigned long last_debounce_time = 0; // The last time the output pin was toggled void setup() { // Initialize the Serial to communicate with the Serial Monitor. Serial.begin(9600); // initialize the button pin as an pull-up input (HIGH when the switch is open and LOW when the switch is closed) pinMode(BUTTON_PIN, INPUT_PULLUP); } void loop() { // read the state of the switch/button: button_state = digitalRead(BUTTON_PIN); // check to see if you just pressed the button // (i.e. the input went from LOW to HIGH), and you've waited long enough // since the last press to ignore any noise: // If the switch/button changed, due to noise or pressing: if (button_state != prev_state_flick) { // reset the debouncing timer last_debounce_time = millis(); // save the the last flickerable state prev_state_flick = button_state; } if ((millis() - last_debounce_time) > DEBOUNCE_TIME) { // whatever the reading is at, it's been there for longer than the debounce // delay, so take it as the actual current state: // if the button state has changed: if(prev_state_steady == HIGH && button_state == LOW) Serial.println("The button is pressed"); else if(prev_state_steady == LOW && button_state == HIGH) Serial.println("The button is released"); // save the the last steady state prev_state_steady = button_state; } }
  • Compile and upload code to Arduino Nano ESP32 board by clicking Upload button on Arduino IDE
  • Open Serial Monitor on Arduino IDE
  • Keep pressing the button several seconds and then release it.
  • Check out the result on the Serial Monitor. It looks like the below:
COM6
Send
The button is pressed The button is released
Autoscroll Show timestamp
Clear output
9600 baud  
Newline  

⇒ As you can see, you did one press and release, and Arduino Nano ESP32 read one press and release. The chattering is eliminated.

We Made It Simple - Arduino Nano ESP32 Button Debounce Code with Library

To make it easy for newbies, especially when deboucing for multiple buttons, we made a button library, called ezButton. You can learn about ezButton library here.

Arduino Nano ESP32 Button Debounce Code for A Single Button

/* * This Arduino Nano ESP32 code was developed by newbiely.com * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano-esp32/arduino-nano-esp32-button-debounce */ #include <ezButton.h> #define DEBOUNCE_TIME 50 // the debounce time in millisecond, increase this time if it still chatters ezButton button(D2); // create ezButton object for pin D2 void setup() { Serial.begin(9600); button.setDebounceTime(DEBOUNCE_TIME); // set debounce time to 50 milliseconds } void loop() { button.loop(); // MUST call the loop() function first if (button.isPressed()) Serial.println("The button is pressed"); if (button.isReleased()) Serial.println("The button is released"); }

Arduino Nano ESP32 Button Debounce Code for A Multiple Buttons

Let's write debounce code for three buttons.

The wiring diagram

The wiring diagram between Arduino Nano ESP32 and Button Library

This image is created using Fritzing. Click to enlarge image

/* * This Arduino Nano ESP32 code was developed by newbiely.com * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano-esp32/arduino-nano-esp32-button-debounce */ #include <ezButton.h> #define DEBOUNCE_TIME 50 // the debounce time in millisecond, increase this time if it still chatters ezButton button1(D6); // create ezButton object for pin D6 ezButton button2(D7); // create ezButton object for pin D7 ezButton button3(D8); // create ezButton object for pin D8 void setup() { Serial.begin(9600); button1.setDebounceTime(DEBOUNCE_TIME); // set debounce time to 50 milliseconds button2.setDebounceTime(DEBOUNCE_TIME); // set debounce time to 50 milliseconds button3.setDebounceTime(DEBOUNCE_TIME); // set debounce time to 50 milliseconds } void loop() { button1.loop(); // MUST call the loop() function first button2.loop(); // MUST call the loop() function first button3.loop(); // MUST call the loop() function first if (button1.isPressed()) Serial.println("The button 1 is pressed"); if (button1.isReleased()) Serial.println("The button 1 is released"); if (button2.isPressed()) Serial.println("The button 2 is pressed"); if (button2.isReleased()) Serial.println("The button 2 is released"); if (button3.isPressed()) Serial.println("The button 3 is pressed"); if (button3.isReleased()) Serial.println("The button 3 is released"); }

Video Tutorial

Additional Knowledge

  • DEBOUNCE_TIME value depends on the hardware. Different hardware may use different values.
  • The debounce should also apply for on/off switch, limit switch, reed switch, touch sensor ...