SENSORS/ACTUATORS

ESP8266 - Button - LED

This tutorial instructs you how to use the ESP8266 and button to control the LED. We will learn two different applications:

Application 1 - The LED state is synchronized with the button state. In detail:

ESP8266 turns on the LED when the button is being pressed.
ESP8266 turns off the LED when the button is NOT being pressed.

Application 2 - The LED state is toggled each time the button is pressed. More specifically:

If ESP8266 detects that the button has been pressed (changing from a HIGH state to a LOW state), it will turn ON the LED if it's currently OFF, or turn OFF the LED if it's currently ON.
Releasing the button does not affect to the LED state.

In the Application 2, We need to debounce the button to make sure it works properly. We'll figure out why it's important by comparing how the LED behaves when we use the ESP8266 code with and without debouncing the button.

Hardware Preparation

1	×	ESP8266 NodeMCU
1	×	Micro USB Cable
1	×	Push Button
1	×	(Optional) Panel-mount Push Button
1	×	LED
1	×	220 ohm resistor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) 5V Power Adapter for ESP8266
1	×	(Optional) ESP8266 Screw Terminal Adapter

Or you can buy the following sensor kit:

DIYables Sensor Kit 30 types, 69 units

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Overview of LED and Button

If you are unfamiliar with LED and button (including pinout, operation, and programming), the following tutorials can help:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

See more in ESP8266's pinout and how to supply power to the ESP8266 and other components.

Application 1 - The LED state is in sync with the button state

ESP8266 Code

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-button-led */ #define BUTTON_PIN D1 // The ESP8266 pin D1 connected to button #define LED_PIN D7 // The ESP8266 pin D7 connected to led int button_state = 0; // variable for reading the button status void setup() { // Configure the LED pin as a digital output pinMode(LED_PIN, OUTPUT); // Configure the ESP8266 pin as a pull-up input: HIGH when the button is open, LOW when pressed. pinMode(BUTTON_PIN, INPUT_PULLUP); } void loop() { // read the state of the button value: button_state = digitalRead(BUTTON_PIN); // control LED according to the state of button if (button_state == LOW) // if button is pressed digitalWrite(LED_PIN, HIGH); // turn on LED else // otherwise, button is not pressing digitalWrite(LED_PIN, LOW); // turn off LED }

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
Wire the components as shown in the diagram.
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
Connect an ESP8266 to your computer with a USB cable.
Launch the Arduino IDE, and select the correct board and port.
Copy the code and open it in the Arduino IDE.
Click the Upload button on the Arduino IDE to compile and upload the code to the ESP8266.

Press the button and hold it for a few seconds.
Check out the alteration in the LED's condition.

You will see that the LED state is in sync with the button state.

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!

Application 2 - Button toggles LED

ESP8266 Code - Button Toggles LED Without Debouncing

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-button-led */ #define BUTTON_PIN D1 // The ESP8266 pin D1 connected to button #define LED_PIN D7 // The ESP8266 pin D7 connected to led int led_state = LOW; // The current state of LED int button_state; // The current state of button int last_button_state; // The previous state of button void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(BUTTON_PIN, INPUT_PULLUP); // Configure the ESP8266 pin to the input pull-up mode pinMode(LED_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode button_state = digitalRead(BUTTON_PIN); } void loop() { last_button_state = button_state; // save the last state button_state = digitalRead(BUTTON_PIN); // read new state if (last_button_state == HIGH && button_state == LOW) { Serial.println("The button is pressed"); // toggle state of LED led_state = !led_state; // control LED according to the toggled state digitalWrite(LED_PIN, led_state); } }

Code Explanation

You can locate the explanation in the comment lines of the ESP8266 code above.

In the code, the expression led_state = !led_state is equal to the following code:

if(led_state == LOW) led_state = HIGH; else led_state = LOW;

Detailed Instructions

Copy the code and open it in the Arduino IDE.
Upload the code to the ESP8266.
Press release and button several times.
Check out the change in the LED's state.

You may observe that the LED state is toggled every time the button is pressed. However, this behavior may not always be consistent. At times, the LED state may be rapidly toggled multiple times within a single button press, or it may not toggle at all(toggling twice in quick succession which can be difficult to see with the naked eye).

⇒ To solve this problem, we need to debounce for the button.

ESP8266 Code - Button Toggles LED With Debouncing

Debouncing a button can be challenging for beginners. Fortunately, the ezButton library makes it easy.

Why is debouncing necessary? See the ESP8266 - Button Debounce tutorial for more information.

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-button-led */ #include <ezButton.h> #define BUTTON_PIN D1 // The ESP8266 pin D1 connected to button #define LED_PIN D7 // The ESP8266 pin D7 connected to led ezButton button(BUTTON_PIN); // create ezButton object for pin 7; int led_state = LOW; // The current state of LED void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(LED_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode button.setDebounceTime(50); // 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"); // toggle state of LED led_state = !led_state; // control LED according to the toggleed sate digitalWrite(LED_PIN, led_state); } }

Detailed Instructions

Install the ezButton library. Refer to How To for instructions.
Copy the code and open it with Arduino IDE.
Click the Upload button on Arduino IDE to upload the code to the ESP8266.
Press and release the button multiple times.
Check out the LED's state change.

You will see that the LED state is toggled exactly once each time the button is pressed.

Video Tutorial

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