ok. it works perfectly.
But the problem now is that when I start mavproxy from rc.local to forward from USB to network, VRBrain stucks, instead if I wait RPi is up&running and then start mavproxy VRBrain works perfectly.
Tomorrow I'll test pixhawk clone
I start mavproxy as following (I have RPi connected to lan (192.168.2.x) for testing and acting as AccessPoint (network 10.0.1.x)
sudo mavproxy.py --master=/dev/ttyACM0 --out=udpbcast:192.168.2.255:14550 --out=tcpin:192.168.2.210:9999 --out=udpbcast:10.0.2.255:14550