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Application Development

doc/connectivity/bluetooth/bluetooth-dev.rst

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.. _bluetooth-dev:

Application Development #######################

Bluetooth applications are developed using the common infrastructure and approach that is described in the :ref:application section of the documentation.

Additional information that is only relevant to Bluetooth applications can be found on this page.

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

Thread safety

Calling into the Bluetooth API is intended to be thread safe, unless otherwise noted in the documentation of the API function. The effort to ensure that this is the case for all API calls is an ongoing one, but the overall goal is formally stated in this paragraph. Bug reports and Pull Requests that move the subsystem in the direction of such goal are welcome.

.. _bluetooth-hw-setup:

Hardware setup

This section describes the options you have when building and debugging Bluetooth applications with Zephyr. Depending on the hardware that is available to you, the requirements you have and the type of development you prefer you may pick one or another setup to match your needs.

There are 3 possible setups:

#. :ref:Embedded <bluetooth-hw-setup-embedded> #. :ref:External controller <bluetooth-hw-setup-external-ll>

  • :ref:QEMU host <bluetooth-hw-setup-qemu-host>
  • :ref:native_sim host <bluetooth-hw-setup-native-sim-host>

#. :ref:Simulated nRF5x with BabbleSim <bluetooth-hw-setup-bsim>

.. _bluetooth-hw-setup-embedded:

Embedded

This setup relies on all software running directly on the embedded platform(s) that the application is targeting. All the :ref:bluetooth-configs and :ref:bluetooth-build-types are supported but you might need to build Zephyr more than once if you are using a dual-chip configuration or if you have multiple cores in your SoC each running a different build type (e.g., one running the Host, the other the Controller).

To start developing using this setup follow the :ref:Getting Started Guide <getting_started>, choose one (or more if you are using a dual-chip solution) boards that support Bluetooth and then :ref:run the application <application_run_board>).

There is a way to access the :ref:HCI <bluetooth-hci> traffic between the Host and Controller, even if there is no physical transport. See :ref:Embedded HCI tracing <bluetooth-embedded-hci-tracing> for instructions.

.. _bluetooth-hw-setup-external-ll:

Host on Linux with an external Controller

.. note:: This is currently only available on GNU/Linux

This setup relies on a "dual-chip" :ref:configuration <bluetooth-configs> which is comprised of the following devices:

#. A :ref:Host-only <bluetooth-build-types> application running in the :ref:QEMU <application_run_qemu> emulator or the :zephyr:board:native_sim <native_sim> native port of Zephyr #. A Controller, which can be one of the following types:

  • A commercially available Controller
  • A :ref:Controller-only <bluetooth-build-types> build of Zephyr
  • A :ref:Virtual controller <bluetooth_virtual_posix>

.. warning:: Certain external Controllers are either unable to accept the Host to Controller flow control parameters that Zephyr sets by default (Qualcomm), or do not transmit any data from the Controller to the Host (Realtek). If you see a message similar to::

 <wrn> bt_hci_core: opcode 0x0c33 status 0x12

when booting your sample of choice (make sure you have enabled :kconfig:option:CONFIG_LOG in your :file:prj.conf before running the sample), or if there is no data flowing from the Controller to the Host, then you need to disable Host to Controller flow control. To do so, set CONFIG_BT_HCI_ACL_FLOW_CONTROL=n in your :file:prj.conf.

.. _bluetooth-hw-setup-qemu-host:

QEMU

You can run the Zephyr Host on the :ref:QEMU emulator<application_run_qemu> and have it interact with a physical external Bluetooth Controller.

Refer to :ref:bluetooth_qemu_native for full instructions on how to build and run an application in this setup.

.. _bluetooth-hw-setup-native-sim-host:

native_sim

.. note:: This is currently only available on GNU/Linux

The :zephyr:board:native_sim <native_sim> target builds your Zephyr application with the Zephyr kernel, and some minimal HW emulation as a native Linux executable.

This executable is a normal Linux program, which can be debugged and instrumented like any other, and it communicates with a physical or virtual external Controller. Refer to:

  • :ref:bluetooth_qemu_native for the physical controller
  • :ref:bluetooth_virtual_posix for the virtual controller

.. _bluetooth-hw-setup-bsim:

Simulated nRF5x with BabbleSim

.. note:: This is currently only available on GNU/Linux

The :ref:nrf52_bsim <nrf52_bsim> and :ref:nrf5340bsim <nrf5340bsim> boards, are simulated target boards which emulate the necessary peripherals of a nRF52/53 SOC to be able to develop and test Bluetooth LE applications. These boards, use:

  • BabbleSim_ to simulate the nRF5x modem and the radio environment.
  • The POSIX arch and native simulator to emulate the processor, and run natively on your host.
  • Models of the nrf5x HW <https://github.com/BabbleSim/ext_NRF_hw_models/>_

Just like with the :zephyr:board:native_sim <native_sim> target, the build result is a normal Linux executable. You can find more information on how to run simulations with one or several devices in either of :ref:these boards's documentation <nrf52bsim_build_and_run>.

With the :ref:nrf52_bsim <nrf52_bsim>, typically you do :ref:Combined builds <bluetooth-build-types>, but it is also possible to build the controller with one of the :zephyr:code-sample:bluetooth_hci_uart samples in one simulated device, and the host with the H4 driver instead of the integrated controller in another simulated device.

With the :ref:nrf5340bsim <nrf5340bsim>, you can build with either, both controller and host on its network core, or, with the network core running only the controller, the application core running the host and your application, and the HCI transport over IPC.

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.

More Examples

More :zephyr:code-sample-category:sample Bluetooth applications <bluetooth> are available in samples/bluetooth/.

.. _BabbleSim: https://babblesim.github.io/