PySide6.QtBluetooth.QLowEnergyController¶
- class QLowEnergyController¶
The
QLowEnergyController
class provides access to Bluetooth Low Energy Devices. More…Synopsis¶
Methods¶
def
addService()
def
error()
def
errorString()
def
localAddress()
def
mtu()
def
readRssi()
def
remoteAddress()
def
remoteName()
def
role()
def
services()
def
state()
Signals¶
def
connected()
def
disconnected()
def
errorOccurred()
def
mtuChanged()
def
rssiRead()
def
stateChanged()
Static functions¶
def
createCentral()
Note
This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE
Detailed Description¶
QLowEnergyController
acts as the entry point for Bluetooth Low Energy development.Bluetooth Low Energy defines two types of devices; the peripheral and the central. Each role performs a different task. The peripheral device provides data which is utilized by central devices. An example might be a humidity sensor which measures the moisture in a winter garden. A device such as a mobile phone might read the sensor’s value and display it to the user in the greater context of all sensors in the same environment. In this case the sensor is the peripheral device and the mobile phone acts as the central device.
A controller in the central role is created via the
createCentral()
factory method. Such an object essentially acts as a placeholder towards a remote Low Energy peripheral device, enabling features such as service discovery and state tracking.After having created a controller object in the central role, the first step is to establish a connection via
connectToDevice()
. Once the connection has been established, the controller’sstate()
changes toConnectedState
and theconnected()
signal is emitted. It is important to mention that some platforms such as a BlueZ based Linux cannot maintain two connected instances ofQLowEnergyController
to the same remote device. In such cases the second call toconnectToDevice()
may fail. This limitation may disappear at some stage in the future. ThedisconnectFromDevice()
function is used to break the existing connection.The second step after establishing the connection is to discover the services offered by the remote peripheral device. This process is started via
discoverServices()
and has finished once thediscoveryFinished()
signal has been emitted. The discovered services can be enumerated viaservices()
.The last step is to create service objects. The
createServiceObject()
function acts as factory for each service object and expects the service UUID as parameter. The calling context should take ownership of the returnedQLowEnergyService
instance.Any
QLowEnergyService
,QLowEnergyCharacteristic
orQLowEnergyDescriptor
instance which is later created from this controller’s connection becomes invalid as soon as the controller disconnects from the remote Bluetooth Low Energy device.A controller in the peripheral role is created via the
createPeripheral()
factory method. Such an object acts as a peripheral device itself, enabling features such as advertising services and allowing clients to get notified about changes to characteristic values.After having created a controller object in the peripheral role, the first step is to populate the set of GATT services offered to client devices via calls to
addService()
. Afterwards, one would callstartAdvertising()
to let the device broadcast some data and, depending on the type of advertising being done, also listen for incoming connections from GATT clients.- class Error¶
Indicates all possible error conditions found during the controller’s existence.
Constant
Description
QLowEnergyController.NoError
No error has occurred.
QLowEnergyController.UnknownError
An unknown error has occurred.
QLowEnergyController.UnknownRemoteDeviceError
The remote Bluetooth Low Energy device with the address passed to the constructor of this class cannot be found.
QLowEnergyController.NetworkError
The attempt to read from or write to the remote device failed.
QLowEnergyController.InvalidBluetoothAdapterError
The local Bluetooth device with the address passed to the constructor of this class cannot be found or there is no local Bluetooth device.
QLowEnergyController.ConnectionError
The attempt to connect to the remote device failed.
QLowEnergyController.AdvertisingError
The attempt to start advertising failed.
QLowEnergyController.RemoteHostClosedError
The remote device closed the connection.
QLowEnergyController.AuthorizationError
The local Bluetooth device closed the connection due to insufficient authorization.
QLowEnergyController.MissingPermissionsError
The operating system requests permissions which were not granted by the user.
QLowEnergyController.RssiReadError
An attempt to read RSSI (received signal strength indicator) of a remote device finished with error.
- class ControllerState¶
Indicates the state of the controller object.
Constant
Description
QLowEnergyController.UnconnectedState
The controller is not connected to a remote device.
QLowEnergyController.ConnectingState
The controller is attempting to connect to a remote device.
QLowEnergyController.ConnectedState
The controller is connected to a remote device.
QLowEnergyController.DiscoveringState
The controller is retrieving the list of services offered by the remote device.
QLowEnergyController.DiscoveredState
The controller has discovered all services offered by the remote device.
QLowEnergyController.ClosingState
The controller is about to be disconnected from the remote device.
QLowEnergyController.AdvertisingState
The controller is currently advertising data.
- class RemoteAddressType¶
Indicates what type of Bluetooth address the remote device uses.
Constant
Description
QLowEnergyController.PublicAddress
The remote device uses a public Bluetooth address.
QLowEnergyController.RandomAddress
A random address is a Bluetooth Low Energy security feature. Peripherals using such addresses may frequently change their Bluetooth address. This information is needed when trying to connect to a peripheral.
- class Role¶
Indicates the role of the controller object.
Constant
Description
QLowEnergyController.CentralRole
The controller acts as a client interacting with a remote device which is in the peripheral role. The controller can initiate connections, discover services and read and write characteristics.
QLowEnergyController.PeripheralRole
The controller can be used to advertise services and handle incoming connections and client requests, acting as a GATT server. A remote device connected to the controller is in the central role.
Note
The peripheral role is not supported on Windows. In addition on Linux, handling the “Signed Write” ATT command on the server side requires BlueZ 5 and kernel version 3.7 or newer.
See also
- addService(service[, parent=None])¶
- Parameters:
service –
QLowEnergyServiceData
parent –
QObject
- Return type:
Constructs and returns a
QLowEnergyService
object withparent
fromservice
. The controller must be in thePeripheralRole
and in theUnconnectedState
. Theservice
object must be valid.Note
Once the peripheral instance is disconnected from the remote central device or if
disconnectFromDevice()
is manually called, every service definition that was previously added via this function is removed from the peripheral. Therefore this function must be called again before re-advertising this peripheral controller instance. The described behavior is connection specific and therefore not dependent on whetherstopAdvertising()
was called.- connectToDevice()¶
Connects to the remote Bluetooth Low Energy device.
This function does nothing if the controller’s
state()
is not equal toUnconnectedState
. Theconnected()
signal is emitted once the connection is successfully established.On Linux/BlueZ systems, it is not possible to connect to the same remote device using two instances of this class. The second call to this function may fail with an error. This limitation may be removed in future releases.
See also
- connected()¶
This signal is emitted when the controller successfully connects to the remote Low Energy device (if the controller is in the
CentralRole
) or if a remote Low Energy device connected to the controller (if the controller is in thePeripheralRole
). On iOS, macOS, and Android this signal is not reliable if the controller is in thePeripheralRole
. On iOS and macOS the controller only guesses that some central connected to our peripheral as soon as this central tries to write/read a characteristic/descriptor. On Android the controller monitors all connected GATT devices. On Linux BlueZ DBus peripheral backend the remote is considered connected when it first reads/writes a characteristic or a descriptor.- connectionUpdated(parameters)¶
- Parameters:
parameters –
QLowEnergyConnectionParameters
This signal is emitted when the connection parameters change. This can happen as a result of calling
requestConnectionUpdate()
or due to other reasons, for instance because the other side of the connection requested new parameters. The new values can be retrieved fromnewParameters
.See also
- static createCentral(remoteDevice[, parent=None])¶
- Parameters:
remoteDevice –
QBluetoothDeviceInfo
parent –
QObject
- Return type:
Returns a new object of this class that is in the
CentralRole
and has the parent objectparent
. TheremoteDevice
refers to the device that a connection will be established to later.The controller uses the local default Bluetooth adapter for the connection management.
See also
- static createCentral(remoteDevice, localDevice[, parent=None])
- Parameters:
remoteDevice –
QBluetoothDeviceInfo
localDevice –
QBluetoothAddress
parent –
QObject
- Return type:
Returns a new instance of this class with
parent
.The
remoteDevice
must contain the address of the remote Bluetooth Low Energy device to which this object should attempt to connect later on.The connection is established via
localDevice
. IflocalDevice
is invalid, the local default device is automatically selected. IflocalDevice
specifies a local device that is not a local Bluetooth adapter,error()
is set toInvalidBluetoothAdapterError
onceconnectToDevice()
is called.Note that specifying the local device to be used for the connection is only possible when using BlueZ. All other platforms do not support this feature.
Returns a new object of this class that is in the
PeripheralRole
and has the parent objectparent
. Typically, the next steps are to add some services and finally callstartAdvertising()
on the returned object.The controller uses the local default Bluetooth adapter for the connection management.
See also
- static createPeripheral(localDevice[, parent=None])
- Parameters:
localDevice –
QBluetoothAddress
parent –
QObject
- Return type:
Returns a new object of this class that is in the
PeripheralRole
and has the parent objectparent
and is usinglocalDevice
. Typically, the next steps are to add some services and finally callstartAdvertising()
on the returned object.The peripheral is created on
localDevice
. IflocalDevice
is invalid, the local default device is automatically selected. IflocalDevice
specifies a local device that is not a local Bluetooth adapter,error()
is set toInvalidBluetoothAdapterError
.Selecting
localDevice
is only supported on Linux. On other platform, the parameter is ignored.See also
- createServiceObject(service[, parent=None])¶
- Parameters:
service –
QBluetoothUuid
parent –
QObject
- Return type:
Creates an instance of the service represented by
serviceUuid
. TheserviceUuid
parameter must have been obtained viaservices()
.The caller takes ownership of the returned pointer and may pass a
parent
parameter as default owner.This function returns a null pointer if no service with
serviceUuid
can be found on the remote device or the controller is disconnected.This function can return instances for secondary services too. The include relationships between services can be expressed via
includedServices()
.If this function is called multiple times using the same service UUID, the returned
QLowEnergyService
instances share their internal data. Therefore if one of the instances initiates the discovery of the service details, the other instances automatically transition into the discovery state too.See also
- disconnectFromDevice()¶
Disconnects from the remote device.
Any
QLowEnergyService
,QLowEnergyCharacteristic
orQLowEnergyDescriptor
instance that resulted from the current connection is automatically invalidated. Once any of those objects become invalid they remain invalid even if this controller object reconnects.This function does nothing if the controller is in the
UnconnectedState
.If the controller is in the peripheral role, it stops advertising and removes all services which have previously been added via
addService()
. To reuse theQLowEnergyController
instance the application must re-add services and restart the advertising mode by callingstartAdvertising()
.See also
- disconnected()¶
This signal is emitted when the controller disconnects from the remote Low Energy device or vice versa. On iOS and macOS this signal is unreliable if the controller is in the
PeripheralRole
. On Android the signal is emitted when the last connected device is disconnected. On BlueZ DBus backend the controller is considered disconnected when last client which has accessed the attributes has disconnected.- discoverServices()¶
Initiates the service discovery process.
The discovery progress is indicated via the
serviceDiscovered()
signal. ThediscoveryFinished()
signal is emitted when the process has finished.If the controller instance is not connected or the controller has performed the service discovery already this function will do nothing.
Note
Some platforms internally cache the service list of a device which was discovered in the past. This can be problematic if the remote device changed its list of services or their inclusion tree. If this behavior is a problem, the best workaround is to temporarily turn Bluetooth off. This causes a reset of the cache data. Currently Android exhibits such a cache behavior.
- discoveryFinished()¶
This signal is emitted when the running service discovery finishes. The signal is not emitted if the discovery process finishes with an error.
This signal can only be emitted if the controller is in the
CentralRole
.See also
Returns the last occurred error or
NoError
.This signal is emitted when an error occurs. The
newError
parameter describes the error that occurred.See also
- errorString()¶
- Return type:
str
Returns a textual representation of the last occurred error. The string is translated.
- localAddress()¶
- Return type:
Returns the address of the local Bluetooth adapter being used for the communication.
If this class instance was requested to use the default adapter but there was no default adapter when creating this class instance, the returned
QBluetoothAddress
will be null.See also
- mtu()¶
- Return type:
int
Returns the MTU size.
During connection setup, the ATT MTU size is negotiated. This method provides the result of this negotiation. It can be used to optimize packet sizes in some situations. The maximum amount of data which can be transferred in a single packet is mtu-3 bytes. 3 bytes are required for the ATT protocol header.
Before the connection setup and MTU negotiation, the default value of
23
will be returned.Not every platform exposes the MTU value. On those platforms (e.g. Linux) this function always returns
-1
.If the controller is in the
PeripheralRole
, there might be several central devices connected to it. In those cases this function returns the MTU of the last connection that was negotiated.- mtuChanged(mtu)¶
- Parameters:
mtu – int
This signal is emitted as a result of a successful MTU change.
mtu
represents the new value.Note
If the controller is in the
PeripheralRole
, the MTU value is negotiated for each client/central device individually. Therefore this signal can be emitted several times in a row for one or several devices.See also
- readRssi()¶
readRssi() reads RSSI (received signal strength indicator) for a connected remote device. If the read was successful, the RSSI is then reported by
rssiRead()
signal.Note
Prior to calling readRssi(), this controller must be connected to a peripheral. This controller must be created using
createCentral()
.Note
In case Bluetooth backend you are using does not support reading RSSI, the
errorOccurred()
signal is emitted with an error codeRssiReadError
. At the moment platforms supporting reading RSSI include Android, iOS and macOS.- remoteAddress()¶
- Return type:
Returns the address of the remote Bluetooth Low Energy device.
For a controller in the
CentralRole
, this value will always be the one passed in when the controller object was created. For a controller in thePeripheralRole
, this value is one of the currently connected client device addresses. This address will be invalid if the controller is not currently in theConnectedState
.- remoteAddressType()¶
- Return type:
Returns the type of
remoteAddress()
. By default, this value is initialized toPublicAddress
.See also
- remoteDeviceUuid()¶
- Return type:
Returns the unique identifier of the remote Bluetooth Low Energy device.
On macOS/iOS/tvOS CoreBluetooth does not expose/accept hardware addresses for LE devices; instead developers are supposed to use unique 128-bit UUIDs, generated by CoreBluetooth. These UUIDS will stay constant for the same central <-> peripheral pair and we use them when connecting to a remote device. For a controller in the
CentralRole
, this value will always be the one passed in when the controller object was created. For a controller in thePeripheralRole
, this value is invalid.- remoteName()¶
- Return type:
str
Returns the name of the remote Bluetooth Low Energy device, if the controller is in the
CentralRole
. Otherwise the result is unspecified.- requestConnectionUpdate(parameters)¶
- Parameters:
parameters –
QLowEnergyConnectionParameters
Requests the controller to update the connection according to
parameters
. If the request is successful, theconnectionUpdated()
signal will be emitted with the actual new parameters. See theQLowEnergyConnectionParameters
class for more information on connection parameters.Android only indirectly permits the adjustment of this parameter set. The connection parameters are separated into three categories (high, low & balanced priority). Each category implies a pre-configured set of values for
minimumInterval()
,maximumInterval()
andlatency()
. Although the connection request is an asynchronous operation, Android does not provide a callback stating the result of the request. This is an acknowledged Android bug. Due to this bug Android does not emit theconnectionUpdated()
signal.Note
Currently, this functionality is only implemented on Linux kernel backend and Android.
See also
Returns the role that this controller object is in.
The role is determined when constructing a
QLowEnergyController
instance usingcreateCentral()
orcreatePeripheral()
.- rssiRead(rssi)¶
- Parameters:
rssi – int
This signal is emitted after successful read of RSSI (received signal strength indicator) for a connected remote device.
rssi
parameter represents the new value.See also
- serviceDiscovered(newService)¶
- Parameters:
newService –
QBluetoothUuid
This signal is emitted each time a new service is discovered. The
newService
parameter contains the UUID of the found service.This signal can only be emitted if the controller is in the
CentralRole
.See also
- services()¶
- Return type:
.list of QBluetoothUuid
Returns the list of services offered by the remote device, if the controller is in the
CentralRole
. Otherwise, the result is unspecified.The list contains all primary and secondary services.
See also
- setRemoteAddressType(type)¶
- Parameters:
type –
RemoteAddressType
Sets the remote address
type
. The type is required to connect to the remote Bluetooth Low Energy device.This attribute is only required to be set on Linux/BlueZ systems with older Linux kernels (v3.3 or lower), or if CAP_NET_ADMIN is not set for the executable. The default value of the attribute is
RandomAddress
.Note
All other platforms handle this flag transparently and therefore applications can ignore it entirely. On Linux, the address type flag is not directly exposed by BlueZ although some use cases do require this information. The only way to detect the flag is via the Linux kernel’s Bluetooth Management API (kernel version 3.4+ required). This API requires CAP_NET_ADMIN capabilities though. If the local QtBluetooth process has this capability set QtBluetooth will use the API. This assumes that
QBluetoothDeviceDiscoveryAgent
was used prior to callingconnectToDevice()
.See also
- startAdvertising(parameters, advertisingData[, scanResponseData=QLowEnergyAdvertisingData()])¶
- Parameters:
parameters –
QLowEnergyAdvertisingParameters
advertisingData –
QLowEnergyAdvertisingData
scanResponseData –
QLowEnergyAdvertisingData
Starts advertising the data given in
advertisingData
andscanResponseData
, using the parameters set inparameters
. The controller has to be in thePeripheralRole
. Ifparameters
indicates that the advertisement should be connectable, then this function also starts listening for incoming client connections.Providing
scanResponseData
is not required, as it is not applicable for certain configurations ofparameters
.advertisingData
andscanResponseData
are limited to 31 byte user data. If, for example, several 128bit uuids are added toadvertisingData
, the advertised packets may not contain all uuids. The existing limit may have caused the truncation of uuids. In such casesscanResponseData
may be used for additional information.On BlueZ DBus backend BlueZ decides if, and which data, to use in a scan response. Therefore all advertisement data is recommended to set in the main
advertisingData
parameter. If both advertisement and scan response data is set, the scan response data is given precedence.If this object is currently not in the
UnconnectedState
, nothing happens.See also
- state()¶
- Return type:
Returns the current state of the controller.
See also
- stateChanged(state)¶
- Parameters:
state –
ControllerState
This signal is emitted when the controller’s state changes. The new
state
can also be retrieved viastate()
.See also
- stopAdvertising()¶
Stops advertising, if this object is currently in the advertising state.
The controller has to be in the
PeripheralRole
for this function to work. It does not invalidate services which have previously been added viaaddService()
.See also