Switch Input

Once you can write to a pin, read from one. Input alone is enough to build simple games.

Parts

• A tactile switch

Circuit

A tactile switch connects the pins that are diagonal to each other when pressed. Adjacent pins may or may not be connected, so use diagonal pins to avoid mistakes.

Note: ESP32 GPIOs are 3.3 V logic and are not 5 V tolerant. Feed the switch from 3V3, not from the 5V pin.

Program

require 'gpio'
require 'machine'

button = GPIO.new(13, GPIO::IN | GPIO::PULL_DOWN)

loop do
  puts "Button: #{button.high? ? 'Pressed' : 'Released'}"
  Machine.delay_ms(1000)
end

The program polls the button once per second and prints its state. GPIO::PULL_DOWN enables the pin’s internal pull-down resistor, so the pin reads LOW (released) while the switch is open instead of floating. Look up “pull-down” if you want to understand why this matters.

Run

Save the program as gpio_in.rb and put it in /home on the device (see File Transfer), then run it from the shell:

$> ./gpio_in.rb

Button: Released
Button: Released
Button: Pressed
Button: Pressed
Button: Released

The state is printed every second. Press the switch and check that the output changes.