I am very curious about this... I'm wiring up the panel for my friend's RV-8 with Dynon D100 & D120, HS34, GNS-430 and a TruTrack DigiFlight II (which was already purchased before Dynon came out with their autopilot or else he'd probably gone with an all-Dynon system).
Looking thru the install manuals, I noticed that the suggested TruTrak Digiflight II interface to a Garmin 430 wants GPS serial plus ARINC both connected at the same time.
If the Digiflight II can accept either GPS steering via ARINC or possibly VOR/ILS input via ARINC, then can't I just put a simple DPDT toggle switch on the Digiflight II's ARINC-A and ARINC-B inputs and allow the pilot to select either the 430's GPS or VOR/ILS ARINC outputs to drive the autopilot?
If so, then would I also need to drop the GPS rs-232 serial line from feeding the autopilot when VOR/ILS ARINC is selected, perhaps with a 3PDT toggle switch?
EDIT: This may be a big "nevermind".... I just noticed that the TT autopilot that I've got sitting in front of me is only the plain Digiflight II flat pack version, not the -G, -VS, -VSG or -VSGV advanced versions. That means it probably doesn't even have its firmware programmed to read ARINC data inputs. I may talk with the RV8's owner/builder tomorrow and ask him if he's interested in upgrading to one of the more advanced Digiflight II versions.
ANOTHER EDIT: After doing a little more reading on TT's website, it looks like we'd have to completely trade up the Digiflight II with an AP-100 or their "Sorcerer" model to get the a/p to fully be able to track an ILS. Would maybe one of the DF-II versions still be able to laterally track a VOR via ARINC signals?