Connect buttons etc to your Rapsberry Pi
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README.md

Frankenpins

A small library to make working with physical buttons on the Raspberry Pi easier.

Installation

To use Frankenpins using Rubygems:

gem install frankenpins

If you're using Bundler, put the following in your Gemfile:

gem 'frankenpins'

Then run sudo bundle install to install the gem (see 'Sudo' below).

Sudo

You need to run your code as sudo so it can access the GPIO pins.

$ sudo bundle exec bin/start

Pin numbering

Frankenpins uses the WiringPi convention for pin numbering. The wiring pi set has a useful chart.

wiring pi pin numbering chart

Examples

There is demo code in the examples folder showing how to use of each of the components.

Buttons

Frankenpins is event-based.

require 'frankenpins'

button = Frankenpins::Button.new(:pin => 0, :pull => :up)
button.when :pressed do
  puts "Button pressed"
end

Frankenpins.wait

First we create a new button, telling the library that the button is on wiring pi pin number 0, and that the pin's internal pull-up resistor should be used:

button = Frankenpins::Button.new(:pin => 0, :pull => :up)

Then we register a block of code to be called whenever the button is pressed down:

button.when :pressed do
  puts "Button pressed"
end

The button events are:

  • pressed when the button is pushed down
  • released when the button is released
  • changed fires every time the button is pushed down or released

Finally, we tell Frankenpins to keep the program running until we quit it. Otherwise, it would exit and wouldn't be watching for our button presses.

Frankenpins.wait

LEDs

You can control a Light Emitting Diode (LED) connected to WiringPi pin 5 as follows:

require 'frankenpins'

led = Frankenpins::LED.new(:pin => 5)
led.on
sleep(3)
led.off

Brightness

You can specify the brightness of the LED. Brightness can be between 0 (off) and 100 (on) and must be an integer.

require 'frankenpins'

led = Frankenpins::LED.new(:pin => 5)
led.on
led.brightness(50) # 50% brightness

Transitions

Turning an LED on and off is good, but Frankenpins can do better. It allows you to fade the LED over a set duration. on, off and brightness all take a :duration option that specifies the number of seconds to fade over. This example fades the LED on over 1 second, fades to 50% brightness over 1 second and then off over 2 seconds.

require 'frankenpins'

led = Frankenpins::LED.new(:pin => 5)
led.on(:duration => 1)
led.brightness(50, :duration => 1)
led.off(:duration => 2)

You can set a default_transition in seconds which will apply to all calls. This example makes the LED to fade on over 2 seconds and then off over 2 seconds:

require 'frankenpins'

led = Frankenpins::LED.new(:pin => 5)
led.default_duration = 2
led.on
led.off

A note about transitions

The transitions are all queued up but don't stop your code from running. So, if you have:

led.on(:duration => 10)
led.off(:duration => 1)

Your code won't stop for 11 seconds until the transitions have finished, the transitions will happen in the background. This means your main programme may finish before the transitions do, to avoid that use Frankenpins.wait to keep your main code running:

led.on(:duration => 10)
led.off(:duration => 1)
Frankenpins.wait

RGB LEDs

These work in the same way as LEDs above, except that the LED has 4 legs. A common ground and 1 for each colour.

Connect each leg to a pin and tell Frankenpins about it. You can then use them in much the same way as a normal LED, except instead of specifying on overall brightness, you specify a colour to change the LED to.

require 'frankenpins'

led = Frankenpins::RGBLED.new(:pins => { :green => 5, :red => 4, :blue => 1 })
led.on
led.rgb([255, 0, 0])

rgb([r, g, b]) requires a value for red, green, blue from 0-255 where 0 is off and 255 is full brightness.

percentage([r, g, b]) requires a value from 0-100 for each colour where 0 if off and 100 if full brightness.

RGB LEDs also support transitions too, so the following works. This example will make the RGB transition to purple over 2 seconds and then turn off over 1 second.

require 'frankenpins'

led = Frankenpins::RGBLED.new(:pins => { :green => 5, :red => 4, :blue => 1 })
led.default_duration = 2
led.on
led.rgb([0, 255, 255])
led.off(:duration => 1)

Pins

Frankenpins Pin event implementation is based on the great Pi Piper library, and uses a modified version of the Pin class which means you can register for events whenever a pin changes value. Check examples/raw_pin.rb for sample code.

Versioning

We use Semantic Versioning and as this is pre-1.0.0 software, anything may change at any time.

Development

It's very early days for this library so any help is gratefully received.

Raise an issue in Github to discuss what you'd like to see included.