Whilst experimenting with X-Plane DataRef USB interface, with an Arduino UNO and Ethernet shield, I found that I was receiving Null value Datarefs and loosing many of the Datarefs that were being sent.
As a further experiment I switched to using a Teensy and the FlightSimControls Package that came with it. This has been quite successful so I am progressing to a full design along that front.
The current X-Plane Interface is
The physical design uses multiple Arduinos and is documented on the
X-Plane Circuit Design page.
Motor Controls for Cockpit Instruments