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.
This tutorial provides:
- How to debounce for a button on Arduino Nano ESP32 code
- How to debounce for a button on Arduino Nano ESP32 code using library
- How to debounce for multiple buttons on Arduino Nano ESP32 code using library
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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Additionally, some of these links are for products from our own brand, DIYables .
Wiring Diagram
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
- 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:
8
Serial.println("Hello World!");
Message (Enter to send message to 'Arduino Nano ESP32' on 'COM15')
New Line
9600 baud
The button is pressed
The button is pressed
The button is pressed
The button is released
The button is released
⇒ 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.
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
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 ...