Android provides a default Bluetooth stack that supports both Classic Bluetooth and Bluetooth Low Energy. Using Bluetooth, Android devices can create personal area networks to send and receive data with nearby Bluetooth devices.
In Android 4.3 and later, the Android Bluetooth stack provides the ability to implement Bluetooth Low Energy (BLE). To fully leverage the BLE APIs, follow the Android Bluetooth HCI Requirements. Android devices with a qualified chipset can implement either Classic Bluetooth or both Classic Bluetooth and BLE. BLE is not backwards compatible with older Bluetooth chipsets.
In Android 8.0, the native Bluetooth stack is fully qualified for Bluetooth 5. To use available Bluetooth 5 features, the device needs to have a Bluetooth 5 qualified chipset.
A Bluetooth application communicates with the Bluetooth process through Binder. The Bluetooth process uses JNI to communicate with the Bluetooth stack and provides developers with access to various Bluetooth profiles. This diagram shows the general structure of the Bluetooth stack:
Figure 1. Android 8.0 Bluetooth architecture
packages/apps/Bluetooth
,
is packaged as an Android app and implements the Bluetooth services
and profiles at the Android framework layer. This app calls into the native
Bluetooth stack via JNI.
packages/apps/Bluetooth/jni
. The JNI code calls into the
Bluetooth stack when certain Bluetooth operations occur, such as when
devices are discovered.
system/bt
. The stack implements the generic Bluetooth HAL and
customizes it with extensions and configuration changes.
HIDL
defines the interface between the Bluetooth stack and the vendor
implementation. To generate the Bluetooth HIDL files, pass the Bluetooth
interface files into the HIDL generation tool. The interface files are located
in hardware/interfaces/bluetooth
.
The Android 8.0 Bluetooth stack is a fully qualified Bluetooth stack. The qualification listing is on the Bluetooth SIG website under QDID 97584.
The core Bluetooth stack resides in
system/bt
.
Development happens in AOSP, and contributions are welcome.
A Bluetooth system service communicates with the Bluetooth stack through JNI and with applications through Binder IPC. The system service provides developers with access to various Bluetooth profiles. This diagram shows the general structure of the Bluetooth stack:
Figure 2. Android 7.x and earlier Bluetooth architecture
packages/apps/Bluetooth
, is packaged as an Android app and
implements the Bluetooth service and profiles at the Android framework layer.
This app calls into the HAL layer via JNI.
packages/apps/Bluetooth/jni
. The JNI code calls
into the HAL layer and receives callbacks from the HAL when certain Bluetooth
operations occur, such as when devices are discovered.
hardware/libhardware/include/hardware/bluetooth.h
.
Additionally, review all of the
hardware/libhardware/include/hardware/bt_*.h
files.
system/bt
. The stack implements the generic Bluetooth HAL
and customizes it with extensions and configuration changes.
The Bluetooth HAL is located in
/hardware/libhardware/include/hardware/bluetooth.h
.
The bluetooth.h
file contains the basic interface for the
Bluetooth stack, and you must implement its functions.
Profile-specific files are located in the same directory. For details, see the HAL File Reference.