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https://github.com/jwhitehorn/pi_piper

Event driven Raspberry Pi GPIO programming in Ruby
https://github.com/jwhitehorn/pi_piper

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Event driven Raspberry Pi GPIO programming in Ruby

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README 

        
## Overview



[![Build Status](https://travis-ci.org/jwhitehorn/pi_piper.png)](https://travis-ci.org/jwhitehorn/pi_piper)



Pi Piper brings event driven programming to the Raspberry Pi's GPIO pins. Pi Piper works with all revisions of the Raspberry Pi,

and has been tested with Ruby 1.9.3 & 2.0 under both [Raspbian "wheezy"](http://www.raspberrypi.org/downloads) and [Occidentalis v0.2](http://learn.adafruit.com/adafruit-raspberry-pi-educational-linux-distro/occidentalis-v0-dot-2).



To get started:



If you do not already have Ruby installed, first you'll need to:



    sudo apt-get install ruby ruby1.9.1-dev libssl-dev



Despite one of the packages being titled "ruby1.9.1-dev", the above command will install Ruby 1.9.3 (as of January 2013) and the Ruby dev tools.



To install Pi Piper:



    sudo gem install pi_piper



### GPIO



The GPIO pins (or General Purpose I/O pins) are the primary "do anything" pins on the Raspberry Pi. Reading inputs from them is as simple as:



```ruby

require 'pi_piper'

include PiPiper



watch :pin => 23 do

  puts "Pin changed from #{last_value} to #{value}"

end



#Or



after :pin => 23, :goes => :high do

  puts "Button pressed"

end



PiPiper.wait

```



Your block will be called when a change to the pin's state is detected.



When using pins as input, you can use internal resistors to pull the pin

up or pull down. This is important if you use open-collector sensors

which have floating output in some states.



You can set resistors when creating a pin passing a :pull parameter

(which can be :up, :down or :off, which is the default).



```ruby

pin = PiPiper::Pin.new(:pin => 17, :direction => :in, :pull => :up)

```



This way, the pin will always return 'on' if it is unconnected or if the

sensor has an open collector output.



You can later alter the pulling resistors using PiPiper#pull!



Additionally you can use pins as output too:



```ruby

pin = PiPiper::Pin.new(:pin => 17, :direction => :out)

pin.on

sleep 1

pin.off

```



_please note, in the above context "pin" refers to the GPIO number of the Raspberry Pi._



### SPI

Starting with version 1.2, Pi Piper offers SPI support.



```ruby

PiPiper::Spi.begin do

  puts write [0x01, 0x80, 0x00]

end

```



If you are using an operating system that supports `/dev/spidev0.0` like the [adafruit

distro][adafruit-linux] you can also write to the spi using `PiPiper::Spi.spidev_out`



```ruby

# Example writing red, green, blue to a string of WS2801 pixels

PiPiper::Spi.spidev_out([255,0,0,0,255,0,0,0,255])

```

[adafruit-linux]:http://learn.adafruit.com/adafruit-raspberry-pi-educational-linux-distro/overview



### Pulse Width Modulation (PWM)



what is it !? https://en.wikipedia.org/wiki/Pulse-width_modulation



PiPiper allow to use the hardware PWM channel of the bcm2835.....

value should be between 0 and 1, clock between 0 and 19.2MHz, mode blaanced or markspace and range something greater than 0.

Supported pin are : 12, 13, 18, 19, 40, 41, 45, 52, 53

but only 18 is on the header..



```ruby

pwm = PiPiper::Pwm.new pin: 18 #, range: 1024, clock: 19.2.megahertz, mode: :markspace, value: 1, start: false

pwm.value= 0.5

pwm.off # works with stop

pwm.on  # aliased start

```



apparently the clock is rounded to the next 2^n divider of 19.2MHz



## Documentation



API documentation for Pi Piper can be found at [rdoc.info](http://rdoc.info/github/jwhitehorn/pi_piper/frames/).



## Example projects



Looking for more examples/sample code for Pi Piper? Then check out the following example projects, complete with circuit diagrams:



* [Project 1: Morse Code](https://github.com/jwhitehorn/pi_piper/wiki/Project-1:-Morse-Code)

* [Project 2: Simple Switch](https://github.com/jwhitehorn/pi_piper/wiki/Project-2:-Simple-Switch)

* [Project 3: 2-bit counter](https://github.com/jwhitehorn/pi_piper/wiki/Project-3:-2-bit-counter)

* [Project 4: MCP3008](https://github.com/jwhitehorn/pi_piper/wiki/Project-4:-MCP3008)



## Under the hood



PiPiper use the libbcm2835 library from Mike McCauley at airspayce. (distributed with Open Source Licensing GPL V2)



http://www.airspayce.com/mikem/bcm2835/index.html



if you want to upgrade or downgrade the library for compatibility reason, get it and make it a shared object library :



```script

wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.49.tar.gz

tar zxvf bcm2835-1.49.tar.gz && cd bcm2835-1.49

./configure && make

sudo make check

sudo make install

cd src && cc -shared bcm2835.o -o libbcm2835.so

cp libbcm2835.so ~/pi_piper/lib/pi_piper

```



## License



Distributed in accordance with the BSD licence, see LICENCE.md file.



***




Proudly developed exclusively on a [Raspberry Pi](http://www.raspberrypi.org)