Pouco posso ajudar, mas se ainda não o fez, procure por aqui:
http://www.google.com/search?ie=UTF-8&oe=UTF-8&q=arduino+processing&btnG=search&domains=http%3A%2F%2Fwww.arduino.cc%2F&sitesearch=http%3A%2F%2Fwww.arduino.cc%2F
Ou aqui:
http://www.arduino.cc/playground/Interfacing/Processing