You can use the USB port directly. You just have to make changes to a particular file on odroid. Follow the steps in last question to know which file to edit : http://docs.flytbase.com/docs/FlytOS/Debugging/FAQ.html
When a pixhawk is connected to the Odroid , it shows up as
/dev/ttyACM0 . You can confirm this on your Odroid by typing this in the terminal:
Then connecting the usb cable , executing the command again and seeing what has changed in the the command output. I'm pretty sure it will be /dev/ttyACM0, but no harm in checking.
Then the FCU URL will be:
<arg name="fcu_url" value="/dev/ttyACM0:921600" />