developers.home-assistant/docs/bluetooth.md

title	sidebar_label
Bluetooth	Bluetooth

Best practices for integration authors

• When connecting to Bluetooth devices with BleakClient, always use the BLEDevice object instead of the address to avoid the client starting a scanner to find the BLEDevice. Call the bluetooth.async_ble_device_from_address API if you only have the address.

• Call the bluetooth.async_get_scanner API to get a BleakScanner instance and pass it to your library. The returned scanner avoids the overhead of running multiple scanners, which is significant. Additionally, the wrapped scanner will continue functioning if the user changes the Bluetooth adapter settings.

• Avoid reusing a BleakClient between connections since this will make connecting less reliable.

• Fetch a new BLEDevice from the bluetooth.async_ble_device_from_address API each time a connection is made. Alternatively, register a callback with bluetooth.async_register_callback and replace a cached BLEDevice each time a callback is received. The details of a BLEDevice object may change due to a change in the active adapter or environment.

• Use a connection timeout of at least ten (10) seconds as BlueZ must resolve services when connecting to a new or updated device for the first time. Transient connection errors are frequent when connecting, and connections are not always successful on the first attempt. The bleak-retry-connector PyPI package can take the guesswork out of quickly and reliably establishing a connection to a device.

Connectable and non-connectable Bluetooth controllers

Home Assistant has support for remote Bluetooth controllers. Some controllers only support listening for advertisement data and do not support connecting to devices. Since many devices only need to receive advertisements, we have the concept of connectable devices and non-connectable devices. Suppose the device does not require an active connection. In that case, the connectable argument should be set to False to opt-in on receiving data from controllers that do not support making outgoing connections. When connectable is set to False, data from connectable and non-connectable controllers will be provided.

The default value for connectable is True. If the integration has some devices that require connections and some devices that do not, the manifest.json should set the flag appropriately for the device. If it is impossible to construct a matcher to differentiate between similar devices, check the connectable property in the config flow discovery BluetoothServiceInfoBleak and reject flows for devices needing outgoing connections.

Subscribing to Bluetooth discoveries

Some integrations may need to know when a device is discovered right away. The Bluetooth integration provides a registration API to receive callbacks when a new device is discovered that matches specific key values. The same format for bluetooth in manifest.json is used for matching. In addition to the matchers used in the manifest.json, address can also be used as a matcher.

The function bluetooth.async_register_callback is provided to enable this ability. The function returns a callback that will cancel the registration when called.

The below example shows registering to get callbacks when a Switchbot device is nearby.

from homeassistant.components import bluetooth

...

@callback
def _async_discovered_device(service_info: bluetooth.BluetoothServiceInfoBleak, change: bluetooth.BluetoothChange) -> None:
    """Subscribe to bluetooth changes."""
    _LOGGER.warning("New service_info: %s", service_info)

entry.async_on_unload(
    bluetooth.async_register_callback(
        hass, _async_discovered_device, {"service_uuid": "cba20d00-224d-11e6-9fb8-0002a5d5c51b", "connectable": False}, bluetooth.BluetoothScanningMode.ACTIVE
    )
)

The below example shows registering to get callbacks for HomeKit devices.

from homeassistant.components import bluetooth

...

entry.async_on_unload(
    bluetooth.async_register_callback(
        hass, _async_discovered_homekit_device, {"manufacturer_id": 76, "manufacturer_data_first_byte": 6}, bluetooth.BluetoothScanningMode.ACTIVE
    )
)

The below example shows registering to get callbacks for Nespresso Prodigios.

from homeassistant.components import bluetooth

...

entry.async_on_unload(
    bluetooth.async_register_callback(
        hass, _async_nespresso_found, {"local_name": "Prodigio_*")}, bluetooth.BluetoothScanningMode.ACTIVE
    )
)

The below example shows registering to get callbacks for a device with the address 44:33:11:22:33:22.

from homeassistant.components import bluetooth

...

entry.async_on_unload(
    bluetooth.async_register_callback(
        hass, _async_specific_device_found, {"address": "44:33:11:22:33:22")}, bluetooth.BluetoothScanningMode.ACTIVE
    )
)

Fetch the shared BleakScanner instance

Integrations that need an instance of a BleakScanner should call the bluetooth.async_get_scanner API. This API returns a wrapper around a single BleakScanner that allows integrations to share without overloading the system.

from homeassistant.components import bluetooth
  
scanner = bluetooth.async_get_scanner(hass)

Determine if a scanner is running

The Bluetooth integration may be set up but has no connectable adapters or remotes. The bluetooth.async_scanner_count API can be used to determine if there is a scanner running that will be able to receive advertisements or generate BLEDevices that can be used to connect to the device. An integration may want to raise a more helpful error during setup if there are no scanners that will generate connectable BLEDevice objects.

from homeassistant.components import bluetooth

count = bluetooth.async_scanner_count(hass, connectable=True)

Subscribing to unavailable callbacks

To get a callback when the Bluetooth stack can no longer see a device, call the bluetooth.async_track_unavailable API. For performance reasons, it may take up to five minutes to get a callback once the device is no longer seen.

If the connectable argument is set to True, if any connectable controller can reach the device, the device will be considered available. If only non-connectable controllers can reach the device, the device will be considered unavailable. If the argument is set to False, the device will be considered available if any controller can see it.

from homeassistant.components import bluetooth

def _unavailable_callback(info: bluetooth.BluetoothServiceInfoBleak) -> None:
    _LOGGER.debug("%s is no longer seen", info.address)
   
cancel = bluetooth.async_track_unavailable(hass, _unavailable_callback, "44:44:33:11:23:42", connectable=True)

Fetching the bleak BLEDevice from the address

Integrations wishing to avoid the overhead of starting an additional scanner to resolve the address may call the bluetooth.async_ble_device_from_address API, which returns a BLEDevice if the bluetooth integration scanner has recently seen the device. The integration MUST fall back to connecting via the address if the BLEDevice is unavailable.

Suppose the integration wants to receive data from connectable and non-connectable controllers. In that case, it can exchange the BLEDevice for a connectable one when it wants to make an outgoing connection as long as at least one connectable controller is in range.

from homeassistant.components import bluetooth

ble_device = bluetooth.async_ble_device_from_address(hass, "44:44:33:11:23:42", connectable=True)

Checking if a device is present

To determine if a device is still present, call the bluetooth.async_address_present API. This call is helpful if your integration needs the device to be present to consider it available. As this call can be expensive with many devices, we recommend only calling it every five minutes.

from homeassistant.components import bluetooth

bluetooth.async_address_present(hass, "44:44:33:11:23:42", connectable=True)

Fetching all discovered devices

To access the list of previous discoveries, call the bluetooth.async_discovered_service_info API. Only devices that are still present will be in the cache.

from homeassistant.components import bluetooth

service_infos = bluetooth.async_discovered_service_info(hass, connectable=True)

Triggering rediscovery of devices

When a configuration entry or device is removed from Home Assistant, trigger rediscovery of its address to make sure they are available to be set up without restarting Home Assistant. You can make use of the Bluetooth connection property of the device registry if your integration manages multiple devices per configuration entry.

from homeassistant.components import bluetooth

bluetooth.async_rediscover_address(hass, "44:44:33:11:23:42")

Waiting for a specific advertisement

To wait for a specific advertisement, call the bluetooth.async_process_advertisements API.

from homeassistant.components import bluetooth

def _process_more_advertisements(
    service_info: BluetoothServiceInfoBleak,
) -> bool:
    """Wait for an advertisement with 323 in the manufacturer_data."""
    return 323 in service_info.manufacturer_data

service_info = await bluetooth.async_process_advertisements(
    hass
    _process_more_advertisements,
    {"address": discovery_info.address, "connectable": False},
    BluetoothScanningMode.ACTIVE,
    ADDITIONAL_DISCOVERY_TIMEOUT
)

Registering an external scanner

To register an external scanner, call the bluetooth.async_register_scanner API. The scanner must inherit from BaseHaScanner.

from homeassistant.components import bluetooth

cancel = bluetooth.async_register_scanner(hass, scanner, connectable=False)

The scanner will need to feed advertisement data to the central Bluetooth manager in the form of BluetoothServiceInfoBleak objects. The callback needed to send the data to the central manager can be obtained with the bluetooth.async_get_advertisement_callback API.

callback = bluetooth.async_get_advertisement_callback(hass)

callback(BluetoothServiceInfoBleak(...))