BACnet (Building
Automation and Control Networks) is a normed protocol for
building automation and was designed by ASHRAE
(American Society of Heating, Refrigerating and Air-Conditioning
Engineers) in order to provide a consistent and intraoperative
standard for data communication in and with systems of building
automation.
The purpose of the standardization is the
interoperability (collaboration of products and applications of
unequal manufacturers). For the definition of the applied BACnet
devices BIBBs (BACnet Interoperability
Building Blocks) are used, which are a collection of several
BACnet services.
The WinCC OA
BACnet driver assumes the BACnet Operator Workstation (B-OWS)
role. The WinCC OA
BACnet driver uses the services of the BACnet server.
The browsing for BACnet devices and objects
and the creation in WinCC OA
takes place with the aid of the WinCC
OA BACnet HMI. The WinCC OA BACnet Object Library
provides the configuration and visualization of BACnet devices
and objects in WinCC OA.
For further information see BACnet
Object Library and HMI.
Note
For the use of the BACnet driver, WinCC OA BACnet HMI as well
as the WinCC OA
BACnet Object Library are not mandatory, due to the fact that
the BACnet driver can be used as a WinCC OA
default driver and therefore needs no special project structure.
Figure: Client/Server communication
in a redundant system
Mapping BACnet <-> WinCC OA
The BACnet driver maps BACnet properties to data
point elements by using the peripheral address. So a defined data
structure is not required.
The following mappings are expedient from the application
view:
BACnet object <->
WinCC OA
data point type
BACnet object instance <->
WinCC OA data point
BACnet property <->
WinCC OA
data point element (gets the BACnet peripheral address)
BACnet Objects
BACnet models different technological devices
(e.g. motor) of the building automation application as a collection
of objects.
Objects are divided into three classes
simple objects
complex objects
device objects
For a list with all supported objects see chapter
BACnet Object Types.
BACnet Services
The data (properties and objects) are transmitted
to the user by services. The needed services are divided into
five application classes:
Services can be either confirmed
or unconfirmed:
The services are transmitted via the client/server
principle. WinCC OA
acts as client and the BACnet device acts as server.
The client provides the management and operation
station (B-OWS - BACnet Operator Workstation).
In order to guarantee the interoperability of the
devices, the services are additionally divided into three interoperability
sections:
For information about the supported BIBBs per service
see chapter BACnet Interoperability
Building Blocks.
User Interface
The UI of the BACnet driver is composed
of the configuration panel
and the peripheral address panel.
Interface
The transmission of data between sender and
receiver takes place over:
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