[mrpippy]

Apple takes backwards-compatibility very seriously for MFi protocols, because they know that the "accessories" are cars that people keep for a long time. I used to work at a company making iPod car kits--we took an interface from 2006 (with a hard-wired 30-pin connector), hooked it through a FireWire->USB charging adapter, a 30-pin->Lightning adapter, and it worked fine with an iPhone 6.

[izacus]

I distinctly remember iPhones complaining about "obsolete device" when plugging them into a few years old Audi and VW cars around iPhone 4 era. That was then followed up with connectivity and charging issues.

So what was the deal with that?

[monknomo]

I have an old car and it definitely doesn't work with anything newer than a 2G iPhone. No errors indicated, just can't hack it. It does work with a usb stick full of mp3s, though.

[mrpippy]

Could be FireWire charging--the original iPhone and earlier iPods could charge off 12V (FireWire), whereas the 3G and up only took 5V (USB). Adapters were available (although Apple didn't make them themselves)

Also with the early iPhones, if accessories were just "Made for iPod" certified but not "Made for iPhone" (which usually required TDMA emissions testing and iPhone testing) a message would pop up.