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215 lines
9.1 KiB
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215 lines
9.1 KiB
ReStructuredText
BLE Client
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==========
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.. seo::
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:description: Configuration of the BLE client on ESP32.
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:image: bluetooth.svg
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The ``ble_client`` component enables connections to Bluetooth
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Low Energy devices in order to query and control them. This
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component does not expose any sensors or output components itself,
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but merely manages connections to them for use by other components.
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.. note::
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The BLE software stack on the ESP32 consumes a significant
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amount of RAM on the device. As such, you may experience
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frequent crashes due to out-of-memory if you enable many
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other components.
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A maximum of three devices is supported due to limitations in the
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ESP32 BLE stack. If you wish to connect more devices, use additional
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ESP32 boards.
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This component does not (yet) support devices that require
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security settings (eg connecting with a PIN).
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Currently, devices connected with the client cannot be
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supported by other components based on :doc:`/components/esp32_ble_tracker`
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as they listen to advertisements which are only sent by devices
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without an active connection.
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Despite the last point above, the ``ble_client`` component requires
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the ``esp32_ble_tracker`` component in order to discover available
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client devices.
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.. code-block:: yaml
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esp32_ble_tracker:
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ble_client:
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- mac_address: FF:FF:20:00:0F:15
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id: itag_black
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Configuration variables:
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------------------------
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- **mac_address** (**Required**, MAC Address): The MAC address of the BLE device to connect to.
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- **id** (**Required**, :ref:`config-id`): The ID to use for code generation, and for reference by dependent components.
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Automations:
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- **on_connect** (*Optional*, :ref:`Automation <automation>`): An automation to perform
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when the client connects to a device. See :ref:`ble_client-on_connect`.
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- **on_disconnect** (*Optional*, :ref:`Automation <automation>`): An automation to perform
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when the client disconnects from a device. See :ref:`ble_client-on_disconnect`.
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BLE Client Automation
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---------------------
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.. _ble_client-on_connect:
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``on_connect``
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**************
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This automation is triggered when the client connects to the BLE device.
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.. code-block:: yaml
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ble_client:
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- mac_address: 11:22:33:44:55:66
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id: ble_itag
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on_connect:
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then:
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- lambda: |-
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ESP_LOGD("ble_client_lambda", "Connected to BLE device");
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.. _ble_client-on_disconnect:
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``on_disconnect``
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*****************
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This automation is triggered when the client disconnects from a BLE device.
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.. code-block:: yaml
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ble_client:
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- mac_address: 11:22:33:44:55:66
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id: ble_itag
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on_disconnect:
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then:
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- lambda: |-
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ESP_LOGD("ble_client_lambda", "Disconnected from BLE device");
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BLE Overview
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------------
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This section gives a brief overview of the Bluetooth LE architecture
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to help with understanding this and the related components. There are
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plenty of more detailed references online.
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BLE uses the concept of a *server* and a *client*. In simple terms,
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the server is implemented on the device providing services, usually
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these are the devices such as heart monitors, tags, weather stations,
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etc. The client connects to the server and makes use of its services.
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The client will often be an app on a phone, or in the case of ESPHome,
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it's the ESP32 device.
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When a client connects to a server, the client queries for *services*
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provided by the server. Services expose categories of functionality
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on the server. These might be well defined and supported services,
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such as the Battery Level service, Device Information or Heart Rate.
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Or they might be custom services designed just for that device. For
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example the button on cheap iTags uses a custom service.
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Each service then defines one or more *characteristics* which are
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typically the discrete values of that service. For example for the
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Environmental Sensor service characteristics exposed include the
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Wind Speed, Humidity and Rainfall. Each of these may be read-only
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or read-write, depending on their functionality.
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A characteristic may also expose one or more *descriptors*, which carry
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further information about the characteristic. This could be things
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like the units, the valid ranges, and whether notifications (see below)
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are enabled.
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BLE also supports *notifications*. A client continuously polling for
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updates could consume a lot of power, which is undesirable for a
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protocol that's designed to be low energy. Instead, a server can push
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updates to the client only when they change. Depending on their purpose
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and design, a characteristic may allow for notifications to be sent. The
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client can then enable notifications by setting the configuration
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descriptor for the characteristic.
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Each service, characteristic, and descriptor is identified by a
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unique identifier (UUID) that may be between 16 and 128 bits long.
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A client will typically identify a device's capabilities based on
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the UUIDs.
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Once the connection is established, referencing each
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service/characteristic/descriptor by the full UUID would take a
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considerable portion of the small (~23 byte) packet. So the
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characteristics and descriptors also provide a small 2-byte
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*handle* (alias) to maximize available data space.
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Setting Up Devices
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------------------
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Whilst the component can connect to most BLE devices (that do not
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require authentication/pin), useful functionality is only obtained
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through dependent components, such as :doc:`/components/sensor/ble_client`.
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See the documentation for these components for details on setting up
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specific devices.
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In order to use the ``ble_client`` component, you need to enable the
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:doc:`/components/esp32_ble_tracker` component. This will also allow you to discover
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the MAC address of the device.
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When you have discovered the MAC address of the device, you can add it
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to the ``ble_client`` stanza.
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If you then build and upload this configuration, the ESP will listen for
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the device and attempt to connect to it when it is discovered. The component
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will then query the device for all available services and characteristics and
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display them in the log:
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.. code-block:: text
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[18:24:56][D][ble_client:043]: Found device at MAC address [FC:58:FA:B1:F8:93]
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[18:24:56][I][ble_client:072]: Attempting BLE connection to fc:58:fa:b1:f8:93
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[18:24:56][I][ble_client:097]: [fc:58:fa:b1:f8:93] ESP_GATTC_OPEN_EVT
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[18:24:57][I][ble_client:143]: Service UUID: 0x1800
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[18:24:57][I][ble_client:144]: start_handle: 0x1 end_handle: 0x5
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[18:24:57][I][ble_client:305]: characteristic 0x2A00, handle 0x3, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A01, handle 0x5, properties 0x2
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[18:24:57][I][ble_client:143]: Service UUID: 0x1801
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[18:24:57][I][ble_client:144]: start_handle: 0x6 end_handle: 0x6
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[18:24:57][I][ble_client:143]: Service UUID: 0x180A
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[18:24:57][I][ble_client:144]: start_handle: 0x7 end_handle: 0x19
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[18:24:57][I][ble_client:305]: characteristic 0x2A29, handle 0x9, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A24, handle 0xb, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A25, handle 0xd, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A27, handle 0xf, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A26, handle 0x11, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A28, handle 0x13, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A23, handle 0x15, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A2A, handle 0x17, properties 0x2
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[18:24:57][I][ble_client:305]: characteristic 0x2A50, handle 0x19, properties 0x2
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[18:24:57][I][ble_client:143]: Service UUID: F000FFC0045140-00B0-0000-0000-000000
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[18:24:57][I][ble_client:144]: start_handle: 0x1a end_handle: 0x22
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[18:24:57][I][ble_client:305]: characteristic F000FFC1045140-00B0-0000-0000-000000, handle 0x1c, properties 0x1c
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[18:24:57][I][ble_client:343]: descriptor 0x2902, handle 0x1d
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[18:24:57][I][ble_client:343]: descriptor 0x2901, handle 0x1e
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[18:24:57][I][ble_client:305]: characteristic F000FFC2045140-00B0-0000-0000-000000, handle 0x20, properties 0x1c
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[18:24:57][I][ble_client:343]: descriptor 0x2902, handle 0x21
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[18:24:57][I][ble_client:343]: descriptor 0x2901, handle 0x22
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[18:24:57][I][ble_client:143]: Service UUID: 0xFFE0
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[18:24:57][I][ble_client:144]: start_handle: 0x23 end_handle: 0x26
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[18:24:57][I][ble_client:305]: characteristic 0xFFE1, handle 0x25, properties 0x10
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[18:24:57][I][ble_client:343]: descriptor 0x2902, handle 0x26
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[18:24:57][I][ble_client:143]: Service UUID: 0x1802
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[18:24:57][I][ble_client:144]: start_handle: 0x27 end_handle: 0x29
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[18:24:57][I][ble_client:305]: characteristic 0x2A06, handle 0x29, properties 0x4
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The discovered services can then be used to enable and configure other
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ESPHome components, for example Service UUID 0xFFE0 is used for iTag style
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keychain button events, used by the :doc:`/components/sensor/ble_client` component.
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See Also
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--------
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- :doc:`/components/sensor/ble_client`
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- :ref:`Automation <automation>`
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- :apiref:`ble_client/ble_client.h`
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- :ghedit:`Edit`
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