[FYT Android Head Units] dishe2:
Hey, OP here. Just wanted to clarify a few things:

I originally asked the question because it came to my attention that the Atoto units handle Bluetooth a little bit differently than other FYT devices.

I was curious to see how others handle it and if they have the same reconnect issues that the Atoto ones do. I'm fairly certain that very little (if anything) would translate over to other brands, however I'm not fully aware of how other brands do it (I've owned 4 Atoto units so far and can't vouch for any others aside from what I've read here). And even stranger, the "fix" differs between Atoto's own devices (the A6 PF is a 8581 devices, and the S8 is a 7862- I own both units and both have BT updates to change how this works after I explained the problem to them, however the updates are very different).

In Atoto's platform, there are two bluetooth UIs:

1) BT2, which is the standard Android Bluetooth stack. It can be used like any other BT connection in an Android device, good for things like a keyboard or other input devices, OBDii dongles, file transfers, internet tethering, etc.

2) BT1, which is a customized Bluetooth UI to act as a receiver (all the headunit-related functions such as handsfree calls and streaming audio, which aren't part of the AOSP Bluetooth stack). They call this custom one BT1, while the standard Android Bluetooth system gets demoted to BT2, probably because they assume this is the most often used one for anyone expecting headunit-style functionality.

I'm not familiar with other FYT units, but it is my understanding that they have only one unified Bluetooth system, and it is likely a customized one only which is why I see people complaining about only being able to use "official" branded OBD readers instead of allowing any standard BT connection like Atoto (@surfer63, is that about right?).

I'm not 100% sure how it works, but it appears that BT1 might actually rely on separate hardware that exists externally from the rest of the Android system, and only interfaces with it via an app (similar to the way the FM tuner works). Essentially it is a Bluetooth receiver that goes into the MCU mixer and controlled inside the app called BT1. The proof to me that this is the case is that:

1) You can "see itself" when searching for bluetooth devices in BT2. I haven't tried this because it feels like a paradox that would unravel the universe at first, but apparently BT2 can see BT1 as an available Bluetooth speaker, and connect to it for audio.

2) After a factory reset, BT1 retains its paired devices information (because it exists outside of Android).

3) BT1 UI has its own "reset" and sometimes even "update" function (S8 Ultra, more on that in a minute), which implies it is operating on a different set of rules than the rest of the system.

When they initially made the update for my S8 Ultra, I was given a file to "flash the firmware of the bluetooth module". It is NOT a system update, but an update that must be initiated only inside of BT1. It does not effect the rest of the system, it does not even reboot the system. You click update, wait for it to finish, then click reset Bluetooth for good measure.

On the A6 pf (5851 device), I was given an actual firmware update to test when they "fixed" it. And not just a new lsec6316update and config file, but a full blown update. It could be that the rest of the update wasn't necessary and just a line in the config was changed, but I'd doubt that since they said the unit currently did not work the way I asked, and their engineers had to "work on a fix".

Either way, the bottom line here is that the Atoto units work different from each other (S8 vs A6 pf) and both of those work differently from every other FYT device I think, so none of this is cross-device useful IMO. I believe this is why they recommended I tell people to contact customer support rather than share the fix online for others, it appears to be very device specific. And for the record, it works much better on the S8 than the A6. The A6 gets stuck if it sees the previous device when it boots up, whereas the S8 can tell when it gets disconnected to start searching for other previous devices. The systems don't work the same way.