MEBS6005 Lecture 5.pdf

Only for internal circulation during lectures 1

MEBS 6005Lecture 5

Introduction to BACnet


17 Vendor IDs were issued in the

first six weeks of 2011 alone !!!

• ASHRAE/ANSI Standard 135 in

1995

• ISO 16484-5 in 2003

• BSR/ASHRAE Standard 135.1 on

method of testing for conformance


Previous LANs defined for BACnet (Latest BACnet/IP and BACnet/ZigBee)

PTP (point-to-

point)

PTP is unique to BACnet for internetworked communications over

modems and voice grade phone lines. PTP accommodates modern

modem protocols (V.32bis and V.42) and also supports direct cable

connections using the EIA-232 signaling standard. Speed is limited

to from 9.6Kbps to 56.0Kbps.

MS/TP (master

slave/token

passing)

MS/TP is also unique to BACnet and is implemented using the

EIA-485 signaling standard. This is a shielded twisted-pair (STP)

LAN operating at speeds from 9.6Kbps to 76.0Kbps. This LAN

type is low cost.

ARCNET

(ANSI/ATA

878.1)

ARCNET® is a token bus standard. ARCNET can run on a variety

of media at different speeds-from 150Kbps on EIA-485 (STP) up to

7.5Mbps over coaxial cable, STP, or fiber optics. Typically,

ARCNET runs at 2.5Mbps over twisted pair.

Ethernet (ISO

8802-3)

Ethernet is fast, running from 10Mbps to 100Mbps (fast Ethernet),

and runs on a variety of media-STP, coaxial cable, or fiber optics.

Like ARCNET, Ethernet requires a special chip to handle network

communications.

LONtalk LONtalk is a proprietary technology developed by the Echelon

Corporation.


BACnet/IP

• Able to communicate directly with peer devices on their network

• Able to make use of local broadcasts, received by all peer devices on their

network

• Able to send remote broadcasts to devices residing on networks with

different network numbers

• Global broadcasting works

• Devices have a unique address, an IP address, and they know what address

is

• Devices don’t need to know their BACnet network number unless the

device is a BACnet router

• Use User Datagram Protocol (UDP) instead of TCP

• TCP is a connection-oriented protocol has more overhead than UDP and

does not allow “one-to-many” messages

• A BACnet/IP network is a collection of one or more IP domains that are

assigned a single BACnet network number.


• All data in a BACnet system is represented by "objects,"

"properties" and "services.“, enabling BACnet devices from

different manufacturers to interoperate.

• An object, currently 49 object types, may be an AI, AO, BI,

BO, Device, Multi-state Input, Group, Pulse Converter etc.

• Every object has an identifier (such as AI-1), much like what

is now commonly known as a "data point".

• But a data point typically has a single value associated with it,

whereas an object consists of a number of prescribed

properties. It is only through its properties that an object is

monitored and controlled.


• BACnet specifies 123+ properties of objects.

• Three properties, i.e. Object-identifier, Object-

name, and Object-type-must be present in every

object.

• BACnet also may require that certain objects

support specific additional properties.

• Some properties can accept writes, and others can

only be read.


• When a property is read or written to - a service.

• Services are how one BACnet device gets information from

another device, commands a device to perform certain actions

(through its objects and properties, of course), or lets other

devices know that something has happened.

• The only service that is compulsory is the Read-property

service.

• A total of 40+ standard services.

• A specifier or engineer needs to know what objects and

services are supported by which devices, information found in

the device's protocol implementation conformance statement

(PICS).


• Because not all devices need to have the same level of

functionality, BACnet defines conformance classes that

categorize the capabilities and functionality of devices.

• All devices of a certain conformance class have a minimum set

of required features (in the form of objects and services). Such

information is made public in a protocol implementation

conformance statement (PICS)

• The PICS lists what objects are present in the device and

whether the device initiates a service request (asks or commands)

or executes the request (responds or acts). The PICS also

provides you with the conformance class of the device.


An Analog Input Object, such as a thermistor, with 5 properties

• An Analog Input Object can have up to ALL Standard

Properties

• In this example, a query about the Present_Value Property

of this Analog Input Object would get the reply "68.0".


Types of BACnet Objects


• Every BACnet device must have a Device Object, the

Properties of which fully describe the BACnet device to

the network.

• The Object_List Property of the Device Object, for

example, provides a list of every Object contained

within the BACnet device.

• The Vendor_Name, Vendor_Identifier and Model_Name

Properties provide the manufacturer name and model of

the device.

• In addition, BACnet allows manufacturers to provide

proprietary Objects


The BACnet standard identifies 123+ different Properties

of Objects. A different subset of these Properties is

specified for each type of Object. The following table

shows some Properties of an Analog Input Object.


An "application program" running on the

BACnet device issues service requests and

processes them upon receipt.

Each service request issued and service acknowledgment

(reply) returned becomes a message packet transferred

over the network from the sending to the receiving device.


• BACnet defines 40+ Services and classifies them into six

categories:

Alarm and Event Remote Device Management

File Access Object Access

Virtual Terminal Security

• For each of the "Confirmed" services, a reply, typically with

data, is expected

• For each of the "Unconfirmed“ services, no reply is expected


BACnet’s Collapsed OSI Architecture


Interoperability Capability of BACnet

• 6 levels of conformance classes for specifying levels of functionality

• A higher class covers all features of a lower class

• A Class 1 device only needs to implement “ReadProperty” Service

• A Class 2 device also needs to implement “WriteProperty” Service

• Functional Group - a device to support a certain particular function, e.g.

“Clock Functional Group” implements TimeSynchronization Service

• Protocol Implementation Conformance Statement (PICS) provides the

detailed options implemented in the device, including supported

functional groups, standard and proprietary objects, and, standard and

proprietary services

• Still too obscure to specify interactions between devices

• BACnet Interoperability Building Blocks (BIBBs) proposed by Prof.

Mike Newman

• 5 principal areas of BIBBs: data sharing, alarms and events, scheduling,

trending, device management


A Quick Comparison

Between

3 Open Protocols in the World

(up to 2007)

Mainly based on:

STRATAResourceInc., “Investigating Open Systems: Comparing

LonWorks and BACnet”, 2006

Alan Kell and Peter Colebrook, “Open Systems for Homes and Buildings:

Comparing LonWorks and KNX”, 2005


According to IEEE,

An Open System provides capabilities that enable properly

implemented applications to run on a variety of platforms

from multiple vendors, interoperate with other applications,

and present a consistent style of interaction with the User.

Hence, the Open Building System Goals include:

• Implementation of an End-to-End solution that is open,

internationally accepted and published for access by

everybody.

• Interoperable and Interchangeable.

• Multi-Vendor


Konnex technology (Merging between Batibus, EIBA and EHS) : the open,

royalty-free and platform independent standard for home & building control,

approved as a European (EN 50090 - EN 13321-1) and a Worldwide standard

(ISO/IEC 14543).

A Typical

EIB

System


Industry Responses in U.S.

• Focus placed on developing standards that

define open systems

– The leading standards are associated with BACnet and

LONWORKS Systems


History

LonWorks BACnet KNX

1988 developed by

Echelon

1994 LonMark

1995 1st LonMark

Certified Device

1999 ANSI 709

2005 600th LonMark

Certified Device

1987 ASHRAE SPC-

135

1995 ASHRAE-135

2000 BTL

2001 ANSI standard

2003 ISO 16484-5

2003 ASHRAE-135.1

2004 BACnet 2004

became ANSI standard

2005 100th BTL Listed

Device

1988 EIB User Club

established by

Siemens

1999 May KNX

formed

2003 Dec EN 50090

by CENELEC

2006 EN13321-1 by

CEN

2006 July ISO/IEC

14543


Network Architecture

LonWorks BACnet KNX

Bottom Up

Flat Topology

Peer-to-Peer

Top Down

Tiered Network

Topology

Low Speed Free

Topology

Network Management

LonWorks BACnet KNX

LNS – around 30 tools

Single tool for all

vendors’ devices

Around 5 independent

tools

No single tool for all

vendors – vendor

dependent

ETS 3(Engineering

Tool Software) which

is manufacturer and

vendor independent


Device Architecture

LonWorks BACnet KNX

Neuron Chip

Neuron C

3rd Party uP

Processor

independent

Language

independent

68HC05 and

ASIC initially

ISO/OSI Implementation

LonWorks BACnet KNX

All 7 Layers 1,2,3 and 7 1,2,3,4 and 7


Operator Interface Software

LonWorks BACnet KNX

Mainly LNS based

DDE and OPC

available

DDE and OPC available EIB Integrated

Development

Environment

Design Guidelines

LonWorks BACnet KNX

LonMark FPs

LonMark FPs in

development

SNVTs

SCPTs

PICS and BIBBs

Data Types

Standard Objects

BIBBs

Device Profiles

KNX Profiles in

Volume 6 of KNX

Specification


Certification

LonWorks BACnet KNX

By LonMark FPs BTL Listed Products KNX certified

standardized data

types and agreed

functional blocks, with

KNX trademark

Devices

LonWorks BACnet KNX

Routers, web servers,

gateways, NICs,

HVAC and non-

HVAC, data collectors

Routers, supervisory

devices, gateways,

HVAC and non-HVAC

as lighting and motor

control

Mainly electrical

wiring devices and

lighting; HVAC

products not strong


Physical Media

LonWorks BACnet KNX

STP or UTP at

78.1k or 1.25M

Powerline

PL3120/50 at

4.8k

Wireless, fibre,

infrared

published, but not

very common

Ethernet,

ARCNET,

MS/TP, LON,

PTP

STP at 9.6k

PL110 and

PL132 at 1.2k

to 2.4k

Wireless at

38.4k


Internet Connectivity

LonWorks BACnet KNX

Lon over IP standardized

in EIA-852 published in

2001

i.LON

Panoramix Enterprise

Platform

Networked Energy

Services

XML

Web services devices

very common by

different vendors

XML WG produced

BACnet/WS interface

EIBnet over Ethernet,

UDP/IP and TCP/IP,

extended to ANubis

(advanced Network

for Unified Building

Integration Services


Distribution

LonWorks BACnet KNX

Lots of solution

independent devices

(HVAC, lighting,

sensors, motor control,

power metering,

security, diagnostic

tools etc.

Direct from

manufacturers as part of

a complete solution

Very few solution

independent devices

Some solution

independent devices

but mainly for

electrical installers,

such as I/O modules,

wall switches,

dimmers, thermostats,

occupancy sensors etc.

MEBS6005 Lecture 5.pdf

Documents

bacnet devices

device object

internal circulation

properties of objects

bacnet system

types of bacnet objects

standard properties

object types