Yes ofcourse there is a lot of information, and indeed I did the google trick
Maybe I should rephrase my question

What is the best way / solution to implement an arduino with raspberry pi for domoticz through USB.
Maybe we should create a page specifically for all I/O possibilities for use with the Raspberry
PiFace(2) v.s. arduino advantages/disadvantages.
Something like:
- Arduino:
Pro's : Cheap, easy through USB, lot's of I/O
Con's : Extra USB port needed on RPI, Extra power consumption (not much), need to program at 2 levels, arduino sketch & RPI to interface
- PiFace:
Pro's : Directly attached to RPI, no additional USB Ports needed, Directly supported by Domomticz, 8 digital inputs / outputs, 2 relays, easy to config
Con's: Expensive, not always working on the RPI (different firmware's etc..)
- Onewire:
Pro's : ...
Con's : ...
- GPIO :
Pro's : ...
Con's :...
...