Using this library with Companion Device

[jonbhanson]

Is it possible to use this library with Android's Companion Device mode? If so, is there an example available?

[philips77]

This depends.

Some DFU modes require the device to advertise with an incremented MAC address in bootloader mode. For that, the app needs to scan for the new device, so you need to have BLUETOOTH_SCAN permission granted in runtime by the user (Android 12+). This applies to devices that aren't using bonding, or updates that update Soft Device (as the bond information may get erased after SD is upgraded.

You could also use Companion Device mode to scan for the device already in bootloader mode and pass this BluetoothDevice object to the library:

1. use ACD in the app to find the device in app mode
2. when user decides to update, send "Jump to bootloader mode" command (see DFU spec)
3. the device will restart to DFU bootloader mode and will advertise with incremented MAC address
4. use ACD again for the user to select the "new" device
5. pass received BluetoothDevice's address to the DFU library.

It may also be possible to skip 3-4 and just add +1 to the last byte of the normal MAC address manually, but the phone needs to scan it at least once after it switched to bootloade mode, so that it knows the address type (public/random). It doesn't mean that your app needs to scan, it can be any app, including the system.