How exactly does that work?
There were 3rd party libraries that would work w/ Android 4.1's bluetooth stack, but Samsung never released DLLs to make that work, so the S3 never had BLE support.
Androidd 4.2 rewrote the bluetooth stack so the 3rd party libraries no longer work and there is no API for it.
How exactly does the S4 have BLE support?
There were 3rd party libraries that would work w/ Android 4.1's bluetooth stack, but Samsung never released DLLs to make that work, so the S3 never had BLE support.
Androidd 4.2 rewrote the bluetooth stack so the 3rd party libraries no longer work and there is no API for it.
How exactly does the S4 have BLE support?
