Teoría sobre I2C y SPI
http://quick2wire.com/articles/i2c-and-spi/
Conectar por USB GPOI I2C
http://blog.oscarliang.net/connect-raspberry-pi-and-arduino-usb-cable/
http://blog.oscarliang.net/raspberry-pi-and-arduino-connected-serial-gpio/
http://blog.oscarliang.net/use-gpio-pins-on-raspberry-pi/
http://blog.oscarliang.net/raspberry-pi-arduino-connected-i2c/
Instalación I2C en Raspberry PI
http://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c
http://www.skpang.co.uk/blog/archives/575
Conectar y comunicar mediante I2C
http://tronixstuff.com/tutorials/
http://tronixstuff.com/2010/10/20/tutorial-arduino-and-the-i2c-bus/
http://tronixstuff.com/2010/10/29/tutorial-arduino-and-the-i2c-bus-part-two/
Librería Wire.h para comunicación I2C e info sobre Arduino Mega 2560
http://mindstormsyarduino.blogspot.com.es/2011/03/arduno-y-la-comunicacion-i2c-libreria.html
Libreria wire (twowire)
http://arduino.cc/en/Reference/Wire
