Qt KNX Datapoint Type Classes

A datapoint type represents the data corresponding to a KNX device functionality. It describes the data, setting the rules about the format and values to be allowed, and it holds the bytes containing the data.

A datapoint type is identified by its main number and a sub number. Each main number corresponds to a datapoint type with a particular structure. The sub numbers correspond to different interpretations or naming of this structure.

The Qt KNX module provides a class for each datapoint type with the main number less than 30 and sub number less than 100. All datapoint types with the same main number inherit from a datapoint type class representing the main number datapoint type characteristics.

Datapoint types are used in the data part of the QKnxTpdu class, which is a part of a link layer frame (QKnxLinkLayerFrame) that is transmitted over a tunneling connection (QKnxNetIpTunnel).

Creating Datapoint Types

QKnxDatapointType is the base class for all datapoint types. It is inherited by two main datapoint type classes: QKnxFixedSizeDatapointType for fixed length datapoint types and QKnxVariableSizeDatapointType for variable length datapoint types.

QKnxDatapointType::Type lists the datapoint types that have been implemented in the Qt KNX module with short descriptions and their main and sub numbers. Datapoint types described in the KNX documentation can be added by creating a class that inherits from QKnxFixedSizeDatapointType or QKnxVariableSizeDatapointType and registering this new class using an instance of QKnxDatapointTypeFactory.

The QKnxDatapointTypeFactory class is used to create datapoint types based on their main number and sub number. One or more datapoints can be registered with the factory and then queried based on the main number and sub number.

The following diagram shows the base Qt KNX module datapoint type classes and the classes derived from them for the main datapoint types:

List of Datapoint Type Classes