ZAF Plus Arduino Mega
The Mega Arduino is a micro-controller designed for projects that require many input and output lines. It very easy to use: simply connect it to the Raspberry Pi through a USB cable. You will also need to upload our firmware to your Arduino (see the software section of this wiki). You can daisy-chain two or more Arduino Mega micro-controllers in series to control an almost unlimited number of motors, relays and servos.
You can find the connections detailed in the following diagram.
The two Arduino Mega inside the electronic box