Raspberry PI GPIO access with ruby

One of the main features of the raspberry pi is the GPIO port, a 21 pins connector where you can attach external hardware and have fun.

You can access the GPIO via the C wiringpi library, which happens to have nice bindings for ruby as well , so let’s install it on the raspberry with

gem install wiringpi

Today we’re going to use ruby to monitor a push button that, when pressed, will activate a LED diode.

On the GPIO port we can use pins 0 to 7 either for input or output (see then complete reference for GPIO pins here). We’re going to use pin 1 for the button and pin 4 for the LED.

So, the connections from the GPIO port to the breadboard with electric parts are as follows:

Now that the hardware is ready, let’s write some code:

require 'wiringpi'

# initialize the GPIO port:
gpio = WiringPi::GPIO.new
# name the pins, for easier reference:
button = 1
led = 4

# initialize the pin functions:
gpio.mode button, INPUT
gpio.mode led, OUTPUT

# turn off the led, just in case:
gpio.write led, 0

# loop on all the pins, when the button pin has 
# 0 value (button is pressed) the led will turn
# on.
loop do
  state = gpio.readAll
  if state[button] == 0
    gpio.write led, 1
  end    
  sleep 0.3
end
  

That’s all folks!