.. _bluetooth:

Bluetooth
#########

.. contents::
    :local:
    :depth: 2

Overview
********

Zephyr comes integrated with a feature-rich and highly configurable
Bluetooth stack:

* Bluetooth 5.0 compliant (ESR10)

* Bluetooth Low Energy Controller support (LE Link Layer)

  * BLE 5.0 compliant
  * Unlimited role and connection count, all roles supported
  * Concurrent multi-protocol support ready
  * Intelligent scheduling of roles to minimize overlap
  * Portable design to any open BLE radio, currently supports Nordic
    Semiconductor nRF51 and nRF52

* Generic Access Profile (GAP) with all possible LE roles

  * Peripheral & Central
  * Observer & Broadcaster

* GATT (Generic Attribute Profile)

  * Server (to be a sensor)
  * Client (to connect to sensors)

* Pairing support, including the Secure Connections feature from Bluetooth 4.2

* Bluetooth Mesh support

  * Relay, Friend Node, Low-Power Node (LPN) and GATT Proxy features
  * Both Provisioning bearers supported (PB-ADV & PB-GATT)
  * Highly configurable, fits as small as 16k RAM devices

* IPSP/6LoWPAN for IPv6 connectivity over Bluetooth LE

  * IPSP node sample application in ``samples/bluetooth/ipsp``

* Basic Bluetooth BR/EDR (Classic) support

  * Generic Access Profile (GAP)
  * Logical Link Control and Adaptation Protocol (L2CAP)
  * Serial Port emulation (RFCOMM protocol)
  * Service Discovery Protocol (SDP)

* Clean HCI driver abstraction

  * 3-Wire (H:5) & 5-Wire (H:4) UART
  * SPI
  * Local controller support as a virtual HCI driver

* Raw HCI interface to run Zephyr as a Controller instead of a full Host stack

  * Possible to export HCI over a physical transport
  * ``samples/bluetooth/hci_uart`` sample for HCI over UART
  * ``samples/bluetooth/hci_usb`` sample for HCI over USB

* Verified with multiple popular controllers

* Highly configurable

  * Features, buffer sizes/counts, stack sizes, etc.


Qualification Testing
*********************

PICS Features
=============

The PICS features for each supported protocol & profile can be found in
the following documents:

.. toctree::
   :maxdepth: 1

   gap-pics.rst
   gatt-pics.rst
   l2cap-pics.rst
   sm-pics.rst
   rfcomm-pics.rst

Qualification Listings
=======================

The Zephyr BLE stack has obtained qualification listings for both the Host
and the Controller.
See the tables below for a list of qualification listings

Host qualifications
-------------------

.. list-table::
   :header-rows: 1

   * - Zephyr version
     - Link
     - Qualifying Company

   * - 1.13
     - `QDID 119517 <https://launchstudio.bluetooth.com/ListingDetails/70189>`__
     - Nordic

Controller qualifications
-------------------------

.. list-table::
   :header-rows: 1

   * - Zephyr version
     - Link
     - Qualifying Company
     - Compatible Hardware

   * - 1.9 to 1.13
     - `QDID 101395 <https://launchstudio.bluetooth.com/ListingDetails/25166>`__
     - Nordic
     - nRF52x


Developing Bluetooth Applications
*********************************

Initialization
===============

The Bluetooth subsystem is initialized using the :c:func:`bt_enable()`
function. The caller should ensure that function succeeds by checking
the return code for errors. If a function pointer is passed to
:c:func:`bt_enable()`, the initialization happens asynchronously, and the
completion is notified through the given function.

Bluetooth Application Example
=============================

A simple Bluetooth beacon application is shown below. The application
initializes the Bluetooth Subsystem and enables non-connectable
advertising, effectively acting as a Bluetooth Low Energy broadcaster.

.. literalinclude:: ../../../samples/bluetooth/beacon/src/main.c
   :language: c
   :lines: 19-
   :linenos:

The key APIs employed by the beacon sample are :c:func:`bt_enable()`
that's used to initialize Bluetooth and then :c:func:`bt_le_adv_start()`
that's used to start advertising a specific combination of advertising
and scan response data.

.. _bluetooth_bluez:

Using BlueZ with Zephyr
=======================

The Linux Bluetooth Protocol Stack, BlueZ, comes with a very useful set of
tools that can be used to debug and interact with Zephyr's BLE Host and
Controller. In order to benefit from these tools you will need to make sure
that you are running a recent version of the Linux Kernel and BlueZ:

* Linux Kernel 4.10+
* BlueZ 4.45+

Additionally, some of the BlueZ tools might not be bundled by default by your
Linux distribution. If you need to build BlueZ from scratch to update to a
recent version or to obtain all of its tools you can follow the steps below:

.. code-block:: console

   git clone git://git.kernel.org/pub/scm/bluetooth/bluez.git
   cd bluez
   ./bootstrap-configure --disable-android --disable-midi
   make

You can then find :file:`btattach`, :file:`btmgt` and :file:`btproxy` in the
:file:`tools/` folder and :file:`btmon` in the :file:`monitor/` folder.

You'll need to enable BlueZ's experimental features so you can access its
most recent BLE functionality. Do this by editing the file
:file:`/lib/systemd/system/bluetooth.service`
and making sure to include the :literal:`-E` option in the daemon's execution
start line:

.. code-block:: console

   ExecStart=/usr/libexec/bluetooth/bluetoothd -E

Finally you can reload and restart the daemon:

.. code-block:: console

   sudo systemctl daemon-reload
   sudo systemctl restart bluetooth

.. _bluetooth_qemu:

Testing with QEMU
==================

It's possible to test Bluetooth applications using QEMU. In order to do
so, a Bluetooth controller needs to be exported from the host OS (Linux)
to the emulator. For this purpose you will need some tools described in the
:ref:`bluetooth_bluez` section.

Using Host System Bluetooth Controller in QEMU
----------------------------------------------

The host OS's Bluetooth controller is connected to the second QEMU
serial line using a UNIX socket. This socket gets used with the help of
the QEMU option :literal:`-serial unix:/tmp/bt-server-bredr`. This
option gets passed to QEMU through :makevar:`QEMU_EXTRA_FLAGS`
automatically whenever an application has enabled Bluetooth support.

On the host side, BlueZ allows to export its Bluetooth controller
through a so-called user channel for QEMU to use:

#. Make sure that the Bluetooth controller is down

#. Use the btproxy tool to open the listening UNIX socket, type:

   .. code-block:: console

      sudo tools/btproxy -u -i 0
      Listening on /tmp/bt-server-bredr

   You might need to replace :literal:`-i 0` with the index of the Controller
   you wish to proxy.

#. Choose one of the Bluetooth sample applications located in
   :literal:`samples/bluetooth`.

#. To run a Bluetooth application in QEMU, type:

.. zephyr-app-commands::
   :zephyr-app: samples/bluetooth/<sample>
   :host-os: unix
   :board: qemu_x86
   :goals: run
   :compact:

Running QEMU now results in a connection with the second serial line to
the :literal:`bt-server-bredr` UNIX socket, letting the application
access the Bluetooth controller.

.. _bluetooth_ctlr_bluez:

Testing Zephyr-based Controllers with BlueZ
============================================

If you want to test a Zephyr-powered BLE Controller using BlueZ's Bluetooth
Host, you will need a few tools described in the :ref:`bluetooth_bluez` section.
Once you have installed the tools you can then use them to interact with your
Zephyr-based controller:

   .. code-block:: console

      sudo tools/btmgmt --index 0
      [hci0]# auto-power
      [hci0]# find -l

You might need to replace :literal:`--index 0` with the index of the Controller
you wish to manage.
Additional information about :file:`btmgmt` can be found in its manual pages.


Source tree layout
******************

The stack is split up as follows in the source tree:

``subsys/bluetooth/host``
  The host stack. This is where the HCI command & event handling
  as well as connection tracking happens. The implementation of the
  core protocols such as L2CAP, ATT & SMP is also here.

``subsys/bluetooth/controller``
  Bluetooth Controller implementation. Implements the controller-side of
  HCI, the Link Layer as well as access to the radio transceiver.

``include/bluetooth/``
  Public API header files. These are the header files applications need
  to include in order to use Bluetooth functionality.

``drivers/bluetooth/``
  HCI transport drivers. Every HCI transport needs its own driver. E.g.
  the two common types of UART transport protocols (3-Wire & 5-Wire)
  have their own drivers.

``samples/bluetooth/``
  Sample Bluetooth code. This is a good reference to get started with
  Bluetooth application development.

``tests/bluetooth/``
  Test applications. These applications are used to verify the
  functionality of the Bluetooth stack, but are not necessary the best
  source for sample code (see ``samples/bluetooth`` instead).

``doc/subsystems/bluetooth/``
  Extra documentation, such as PICS documents.