QLowEnergyCharacteristic#

The QLowEnergyCharacteristic class stores information about a Bluetooth Low Energy service characteristic. More…

Synopsis#

Functions#

def clientCharacteristicConfiguration ()
def descriptor (uuid)
def descriptors ()
def isValid ()
def name ()
def __ne__ (b)
def __eq__ (b)
def properties ()
def uuid ()
def value ()

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#

QLowEnergyCharacteristic provides information about a Bluetooth Low Energy service characteristic’s name() , uuid() , value() , properties() , and descriptors() . To obtain the characteristic’s specification and information, it is necessary to connect to the device using the QLowEnergyService and QLowEnergyController classes.

The characteristic value may be written via the QLowEnergyService instance that manages the service to which this characteristic belongs. The writeCharacteristic() function writes the new value. The characteristicWritten() signal is emitted upon success. The value() of this object is automatically updated accordingly.

Characteristics may contain none, one or more descriptors. They can be individually retrieved using the descriptor() function. The descriptors() function returns all descriptors as a list. The general purpose of a descriptor is to add contextual information to the characteristic. For example, the descriptor might provide format or range information specifying how the characteristic’s value is to be interpreted.

See also

QLowEnergyService QLowEnergyDescriptor

class PySide6.QtBluetooth.QLowEnergyCharacteristic#

PySide6.QtBluetooth.QLowEnergyCharacteristic(other)

Parameters:: other – PySide6.QtBluetooth.QLowEnergyCharacteristic

Construct a new QLowEnergyCharacteristic . A default-constructed instance of this class is always invalid.

See also

isValid()

Construct a new QLowEnergyCharacteristic that is a copy of other.

The two copies continue to share the same underlying data which does not detach upon write.

PySide6.QtBluetooth.QLowEnergyCharacteristic.PropertyType#

(inherits enum.Flag) This enum describes the properties of a characteristic.

Constant

Description

QLowEnergyCharacteristic.Unknown

The type is not known.

QLowEnergyCharacteristic.Broadcasting

Allow for the broadcasting of Generic Attributes (GATT) characteristic values.

QLowEnergyCharacteristic.Read

Allow the characteristic values to be read.

QLowEnergyCharacteristic.WriteNoResponse

Allow characteristic values without responses to be written.

QLowEnergyCharacteristic.Write

Allow for characteristic values to be written.

QLowEnergyCharacteristic.Notify

Permits notification of characteristic values.

QLowEnergyCharacteristic.Indicate

Permits indications of characteristic values.

QLowEnergyCharacteristic.WriteSigned

Permits signed writes of the GATT characteristic values.

QLowEnergyCharacteristic.ExtendedProperty

Additional characteristic properties are defined in the characteristic’s extended properties descriptor.

Constant	Description
QLowEnergyCharacteristic.Unknown	The type is not known.
QLowEnergyCharacteristic.Broadcasting	Allow for the broadcasting of Generic Attributes (GATT) characteristic values.
QLowEnergyCharacteristic.Read	Allow the characteristic values to be read.
QLowEnergyCharacteristic.WriteNoResponse	Allow characteristic values without responses to be written.
QLowEnergyCharacteristic.Write	Allow for characteristic values to be written.
QLowEnergyCharacteristic.Notify	Permits notification of characteristic values.
QLowEnergyCharacteristic.Indicate	Permits indications of characteristic values.
QLowEnergyCharacteristic.WriteSigned	Permits signed writes of the GATT characteristic values.
QLowEnergyCharacteristic.ExtendedProperty	Additional characteristic properties are defined in the characteristic’s extended properties descriptor.

It is not recommended to set both Notify and Indicate properties on the same characteristic as the underlying Bluetooth stack behaviors differ from platform to platform. Please see clientCharacteristicConfiguration

See also

properties()

PySide6.QtBluetooth.QLowEnergyCharacteristic.CCCDDisable#

PySide6.QtBluetooth.QLowEnergyCharacteristic.CCCDEnableNotification#

PySide6.QtBluetooth.QLowEnergyCharacteristic.CCCDEnableIndication#

PySide6.QtBluetooth.QLowEnergyCharacteristic.clientCharacteristicConfiguration()#

Return type:: PySide6.QtBluetooth.QLowEnergyDescriptor

Returns the Client Characteristic Configuration Descriptor or an invalid QLowEnergyDescriptor instance if no Client Characteristic Configuration Descriptor exists.

BTLE characteristics can support notifications and/or indications. In both cases, the peripheral will inform the central on each change of the characteristic’s value. In the BTLE attribute protocol, notification messages are not confirmed by the central, while indications are confirmed. Notifications are considered faster, but unreliable, while indications are slower and more reliable.

If a characteristic supports notification or indication, these can be enabled by writing special bit patterns to the Client Characteristic Configuration Descriptor. For convenience, these bit patterns are provided as QLowEnergyCharacteristic::CCCDDisable , QLowEnergyCharacteristic::CCCDEnableNotification , and QLowEnergyCharacteristic::CCCDEnableIndication .

Enabling e.g. notification for a characteristic named mycharacteristic in a service called myservice could be done using the following code.

auto cccd = mycharacteristic.clientCharacteristicConfiguration();
if (!cccd.isValid()) {
    // your error handling
    return error;
}
myservice->writeDescriptor(cccd, QLowEnergyCharacteristic::CCCDEnableNotification);

Note

Calling characteristic.clientCharacteristicConfiguration() is equivalent to calling characteristic.descriptor(QBluetoothUuid::DescriptorType::ClientCharacteristicConfiguration).

Note

It is not recommended to use both notifications and indications on the same characteristic. This applies to both server-side when setting up the characteristics, as well as client-side when enabling them. The bluetooth stack behavior differs from platform to platform and the cross-platform behavior will likely be inconsistent. As an example a Bluez Linux client might unconditionally try to enable both mechanisms if both are supported, whereas a macOS client might unconditionally enable just the notifications. If both are needed consider creating two separate characteristics.