c_GPIO

c_GPIO is a rubygem for controlling GPIO Ports of raspberry PIs out of ruby.

It provides an easy to use interface for accessing the GPIO feature. c_GPIO is written in C to be as close as possible to the system.

I also wrote this as ruby c extension to learn a bit about C.

c_GPIO provides predefined classes for

• LED
• Buttons

There is a base class available as well which provides manual setting of direction (IN / OUT) and value (HIGH / LOW).

Usage / Examples

Here you will find various examples for this gem.

Turning a LED on and off

require 'c_gpio'

led = GPIO::Led.new(2) # Initialize a LED connected to PIN 2

led.turn_on! # Turn on the LED

sleep(1) # Wait a second

led.turn_off! # Turn off the LED

Connect a button to GPIO

require 'c_gpio'

button = GPIO::Button.new(2) # Initialize a button connected to PIN 2

# pressed? will return true, if the button is being pressed,
# otherwise it will return false
if(button.pressed?) {
  puts "The button is currently pressed"
}

# If you want to get notified, once a button is pressed or released,
# You can easily use one (or both) of the following callbacks

button.on_press do
    puts "You pressed da button"
end

button.on_release do
    puts "ou stopped pressing the button"
end

Controlling a PWM Engine

Please note that this is experimental. This gem will create a PWM signal using the CPU which might not be that accurate. You can still try it and you are welcome to have a look at the implementation if. Give feedback an collaborate in optimizing it.

require 'c_gpio'

stepper = GPIO::Pwm.new(2) # Initialize a stepping motor connected to PIN 2

# Move the stepper to the one side (0 is the lowest value you can submit)
stepper.move_to(0)

# Move the stepper to the middle position
stepper.move_to(100)

# Move the stepper to the other side (200 is the highest value you can submit)
stepper.move_to(200)

Because of the CPU of a PI being unprecise, this class stopps sending a PWM signal after ~1400ms. Your stepper will have to reach it's final position after this time. I decided to stop the PWM signal after 1400ms because otherwise, the stepper will start jittering. The reason for this that generating a PWM signal from the CPU is not that accurate as from an arduino. If you know a more precise implementation of PWM signals, feel free to contact me.

Using the Base class for reading custom parts

require 'c_gpio'

io = GPIO::Base.new(2) # We want to read from PIN 2

io.direction = :in # Setting the direction to "in", so we can read

io.value # will return :high or :low depending on what your sensor says

Using the Base class for writing custom parts

require 'c_gpio'

io = GPIO::Base.new(2) # We want to write to PIN 2

io.direction = :out # Setting the direction to "out", so we can write

io.value = :high # will power the connected part on

io.value = :low # will power the connected part off

Using callbacks of the Base class

Those callbacks can be used for both directions, "IN" and "OUT". Using them you can observe, if your peripheral device changed the signal from HIGH to LOW or from LOW to HIGH. If the direction is set to "OUT", you also can observe, if someone is changing the outgoing signal.

require 'c_gpio'

io = GPIO::Base.new(2) # We want to write to PIN 2

io.direction = :in

io.on_high do
    puts "signal changed to HIGH"
end

io.on_low do
    puts "signal changed to low"
end

License

MIT

Free Software, Hell Yeah!

Finally

I wrote this as my fist c program and my first c extension. I have to Idea if this code is looking pretty or optimized.

But I am open to everyone who wants to give feedback or collaborate in this.