5.1 Reading Button Value

In this interactive project, we’ll venture into the realm of button controls and LED manipulation.

The concept is straightforward yet effective. We’ll be reading the state of a button. When the button is pressed down, it registers a high voltage level, or ‘high state’. This action will then trigger an LED to light up.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
ESP32 Starter Kit	320+	ESP32 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
ESP32 WROOM 32E	BUY
ESP32 Camera Extension	-
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
LED	BUY
Button	BUY

Available Pins

• Available Pins

  Here is a list of available pins on the ESP32 board for this project.

  For Input	IO14, IO25, I35, I34, I39, I36, IO18, IO19, IO21, IO22, IO23
  For Output	IO13, IO12, IO14, IO27, IO26, IO25, IO33, IO32, IO15, IO2, IO0, IO4, IO5, IO18, IO19, IO21, IO22, IO23

• Conditional Usage Pins (Input)

  The following pins have built-in pull-up or pull-down resistors, so external resistors are not required when using them as input pins:

  Conditional Usage Pins	Description
  IO13, IO15, IO2, IO4	Pulling up with a 47K resistor defaults the value to high.
  IO27, IO26, IO33	Pulling up with a 4.7K resistor defaults the value to high.
  IO32	Pulling down with a 1K resistor defaults the value to low.

• Strapping Pins (Input)

  Strapping pins are a special set of pins that are used to determine specific boot modes during device startup (i.e., power-on reset).

  Strapping Pins

  IO5, IO0, IO2, IO12, IO15

  Generally, it is not recommended to use them as input pins. If you wish to use these pins, consider the potential impact on the booting process. For more details, please refer to the Strapping Pins section.

Schematic

To ensure proper functionality, connect one side of the button pin to 3.3V and the other side to IO14. When the button is pressed, IO14 will be set to high, causing the LED to light up. When the button is released, IO14 will return to its suspended state, which may be either high or low. To ensure a stable low level when the button is not pressed, IO14 should be connected to GND through a 10K pull-down resistor.

Wiring

Note

A four-pin button is designed in an H shape. When the button is not pressed, the left and right pins are disconnected, and current cannot flow between them. However, when the button is pressed, the left and right pins are connected, creating a pathway for current to flow.

Code

Note

• Open the 5.1_read_button_value.py file located in the esp32-starter-kit-main\micropython\codes path, or copy and paste the code into Thonny. Then, click “Run Current Script” or press F5 to execute it.

• Make sure to select the “MicroPython (ESP32).COMxx” interpreter in the bottom right corner.

import machine
import time

button = machine.Pin(14, machine.Pin.IN) # Button pin
led = machine.Pin(26, machine.Pin.OUT) # LED pin


while True:
    # If the button is pressed by reading its value
    if button.value() == 1:
        # Turn on the LED by setting its value to 1
        led.value(1)
#         time.sleep(0.5)
    else:
        # Turn off the LED
        led.value(0)

During script execution, the LED lights up when you press the button and goes out when you release it.