Bluetooth Overview

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I. Introduction

openvela Bluetooth is certified for Bluetooth 5.4. Supported Bluetooth capabilities include:

• Core
  • BR/EDR/BLE
  • GAP
  • L2CAP
  • GATT Client/Server
• A2DP SRC/SNK
• AVRCP CT/TG
• HFP AG/HF
• PAN
• SPP
• HID
• HOGP
• LEA
  • TMAP
  • CAP
  • BAP/ASCS/PACS/BASS
  • CSIP/CSIS
  • MCP/MCS
  • CCP/TBS
  • VCP/VCS
• Mesh

openvela Bluetooth also supports various open‑source and proprietary stacks, such as Zephyr, BlueZ, Bluedroid, Barrot, etc.

II. Architecture Diagram

• The openvela Bluetooth Framework provides a unified programming API for Android Native, wearables, speakers, IoT, and other applications.
• These APIs cover Bluetooth operations such as power on/off, scanning, connecting, and pairing, all implemented by a comprehensive set of Bluetooth service components.
• To support multiple stacks, the Bluetooth Framework defines a unified Stack Abstraction Layer interface (SAL API), allowing third‑party stacks to integrate easily with OpenVela. When integrating a new stack, in addition to adapting the SAL API, you must also adapt NuttX’s POSIX APIs so that the stack runs efficiently on NuttX.

III. Code Directory

After cloning the frameworks_bluetooth repository, it maps to the frameworks/connectivity/bluetooth folder. The directory structure is as follows:

├── Android.bp                     * Android build configuration *
├── CMakeLists.txt                 * CMake build configuration *
├── feature                        * Directory: QuickApp Feature API *
│   ├── include
│   ├── jidl
│   └── src
├── framework                      * Directory: Bluetooth Framework API *
│   ├── api
│   ├── binder
│   ├── common
│   ├── dbus
│   ├── include                    ** Bluetooth Framework API declarations (for app use) **
│   └── socket
├── frameworkBluetooth.go          * Go file for Android build *
├── img                            * Image files used by README.md *
├── Kconfig                        * Build configuration description *
├── LICENSE                        * License file *
├── Make.defs                      * Adds Bluetooth Framework to NuttX *
├── Make.dep                       * Build dependencies *
├── Makefile                       * Build rules *
├── Makefile.host                  * Host build rules *
├── README.md                      * Repository documentation (English) *
├── README_zh-cn.md                * Repository documentation (Chinese) *
├── service                        * Directory: Bluetooth Services *
│   ├── common
│   ├── ipc
│   ├── profiles
│   ├── src
│   ├── stacks
│   ├── utils
│   ├── vendor
│   └── vhal
├── tests                          * Directory: sample test code *
└── tools                          * Directory: bttool utility code *

IV. Development Guide

1. Bluetooth Application Development

Third‑party application developers can use the openvela QuickApp Feature, a set of C++ APIs built on the QuickJS engine, to access system Bluetooth capabilities. For more details, see Bluetooth API.

Additionally, the Bluetooth Framework provides NDK interfaces to access all Bluetooth system capabilities. Refer to the headers in framework/include for more information.

2. Bluetooth Driver Development

OpenVela Bluetooth supports multiple driver architectures. Below is an example using the common BTH4 driver architecture to implement and register a Bluetooth driver.

Implementing the Driver

Chip vendors implement a variable of type struct bt_driver_s and initialize the following member functions:

• CODE int (*open)(FAR struct bt_driver_s *btdev)
• CODE int (*send)(FAR struct bt_driver_s *btdev, enum bt_buf_type_e type, FAR void *data, size_t len)
• CODE int (*ioctl)(FAR struct bt_driver_s *btdev, int cmd, unsigned long arg)
• CODE void (*close)(FAR struct bt_driver_s *btdev)

These functions depend on the HCI transport between the Host and Controller.

Registering the Driver

After implementing the structure, register the driver instance via the API bt_driver_register():

• int bt_driver_register**(FAR struct bt_driver_s *drv)

See the type definition in nuttx/include/nuttx/wireless/bluetooth/bt_driver.h. The call flow is shown below:

Note

Vendors do not need to define the receive() member; the BTH4 driver initializes it:

• CODE int (*receive)(FAR struct bt_driver_s *btdev, enum bt_buf_type_e type, FAR void *data, size_t len)

When HCI data arrives from the chip, simply call bt_netdev_receive(), which invokes receive() to enqueue the data.

V. Related Repositories

• frameworks_bluetooth: Provides rich Bluetooth application programming interfaces for developers, including API layers, service components, SAL abstraction, and HAL layers. The repo also includes tools like bttool for testing Bluetooth features and sample API usage.
• external_zblue: Based on Zephyr’s stack, enhanced by OpenVela.
• docs: Contains additional technical documentation for the Bluetooth module.