"ok, so the multiplexer is connected to Rx & Tx (i'm using an Arduino Duemilanove) and then you can either send a command to the c328 or send/receive data via Xbee am i right?"

"Hey thanks Jack,

now i looked back at the http://diydrones.com/profiles/blogs/secrets-of-the-c328 i saw a similar schematic already so sorry for that.
As i can see in this schematic you are not sending any data from the ground to the plane via…"

"Hey,

How did you manage to wire the c328 camera and Xbee at the same time since they both use Rx & Tx ?"