Basics of BACnet - kargs.net

1 Basics of BACnet History of BACnet BACnet Architecture routers Gateways Objects Properties Services 2015. Why a Standard Protocol? Interoperability Competitive system expansion End "lock in" fear Integrating building services requires communication standards Reduce training cost by using a single operator interface Enable development of new technology Why a Standard Protocol? Share data among different vendor's systems for a more sensible and integrated approach to facilities management Access all systems from a common interface to permit common graphics, event and alarm enunciation, and data logging History of BACnet Committee began in Design Goals June, 1987 Interoperability Consensus using Efficiency working groups Flexibility ASHRAE/ANSI Extensibility standard 135-1995 Reliability ISO 16484-5 in Stability 2003 Simplicity BACnet Applications HVAC Controls Lighting Controls Security (access control).

2 Fire detection/suppression systems Smart Elevators Fault detection and diagnostic systems BACnet Architecture BACnet Layers OSI. BACnet Application Layer (APDU) Application BACnet Network Layer (NPDU) Network ISO 8802-2 MS/TP PTP BVLC BVLC ZigBee Data Link LonTalk Ethernet ARCNET EIA-485 EIA-232 UDP/IP4 UDP/IP6 Physical LAN options with BACnet Pros? Cons? LAN: PTP. Only choice for modem Point to point only Special design for point to Limited speed ( to point applications 56 Kbps). Accommodates modern modem standards ( , ). LAN: LonTalk Variety of media (UTP, Non-deterministic coax, RF, IR, fiber) Distance limitations Scalable speed (32K to Sole source chip ).

3 Special development tools Application size limited Very few BACnet vendors using LonTalk LAN: ARCNET. Pros Cons ANSI Standard Sole source chip Deterministic response Too costly for low end unitary controllers Scalable speed Distance limitations for Variety of media (UTP, some media coax, fiber). Very few BACnet vendors Very fast ( ). using ARCNET. No special development tools High performance for medium cost LAN: BACnet MS/TP. ANSI standard Single media (EIA-485). Low cost Limited speed ( to 115 Kbps). Can be implemented in a single chip microcontroller Deterministic response Long distance (1500 m).

4 LAN: Ethernet Pros Cons International standard High cost Already in most buildings Distance limitations Variety of media (UTP, non-deterministic fiber, wireless). Very fast (10/100/1000 or more Mbps). Easy to interface to PCs No special development tools Power included (PoE). LAN: BACnet /IP. International standard High cost Already in most buildings Distance limitations Variety of media (UTP, Non-deterministic fiber, wireless) Additional software stack Very fast (10/100/1000 or required (UDP/IP). more Mbps). Easy to interface to PCs No special development tools Power included (PoE).

5 LAN: BACnet /IPv6. International standard Uses VMAC for address New to BACnet (2015) Can use Ethernet, WiFi, 6lowPAN, 6loBAC. Variety of media (UTP, fiber, wireless) Additional software stack required (UDP/IPv6). Standard meshing and messaging built on standard wireless layer (IEEE ). LAN: ZigBee Low cost, low power Limited speeds wireless Limited broadcasting Standard meshing and Nodes may sleep messaging built on standard wireless layer (IEEE ). Internetworking Required whenever two dissimilar LAN. technologies need be coupled Performance constraints (bandwidth). Cost constraints Isolate message traffic Remote access Utilize existing infrastructure Connect multiple isolated applications Start of Message BACnet routers Ethernet NPDU APDU.

6 Address Error and Length Detection Information Checksum BACnet Router Data Remains Unchanged Start of Message NPDU APDU. MS/TP. Address Error and Length Detection Information Checksum BACnet routers Network 2. Network 1 Network 3 Network 4. DMAC=04 DMAC=05 DMAC=08. DNET=4 DNET=4 SNET=1. DADR=08 DADR=08 SADR=05. Port 1 Port 2 Port 3 Port 1 Port 2. MAC 04 MAC 04 MAC 07 MAC 05 MAC 07. Device Device Device MAC 05 Router 1 MAC 08 Router 2 MAC 08. Routing Table Routing Table Net Send To Net Send To 1 Attached, port 1 1 Net 3, MAC 7. 2 Attached, port 2 2 Net 3, MAC 7. 3 Attached, port 3 3 Attached, port 1.

7 4 Net 3, MAC 5 4 Attached, port 2. BACnet Gateway Ethernet NPDU APDU. BACnet Gateway Gateway Configuration tool from Control Solutions, Inc Modbus RTU. Modbus RTU Packet BACnet Objects Objects represent physical inputs, outputs, and software processes. IF level > 50 THEN.. BACnet Objects Objects are evaluated and controlled by their properties Property Name, Value Object_Name "Lighting Area 1". Object_Type BINARY_OUTPUT. Present_Value Active Status_Flags Normal, In-Service Out_Of_Service False Inactive_Text "Off". Active_Text "On". BACnet Objects accumulator binary-output file multi-state-output trend-log analog-input binary-value group multi-state-value load-control analog-output calendar life-safety-point notification-class structured-view analog-value command life-safety-zone program access-door averaging device loop pulse-converter binary-input access-credential event-enrollment multi-state-input schedule event-log access-zone access-rights access-point access-user credential-data-input characterstring-value bitstring-value trend-log-multiple global-group characterstring-value date-pattern-value

8 Date-value datetime-pattern-value datetime-value integer-value large-analog-value octetstring-value positive-integer-value time-pattern-value time-value channel staged-value timer-value lighting-output binary-lighting-output notification-forwarder alert-enrollment network-port elevator BACnet Objects Required and Optional Properties Object_Name "Lighting Area 1". Object_Type BINARY_OUTPUT. Required Present_Value Active Status_Flags Normal, In-Service Out_Of_Service False Inactive_Text "Off". Optional Active_Text "On". Other Binary Output Object Property Identifier Property Datatype Conformance Code Conformance Codes: Object_Identifier BACnetObjectIdentifier R.

9 Object_Name CharacterString R R required, readable Object_Type BACnetObjectType R W required, writable Present_Value BACnetBinaryPV W. Description CharacterString O O optional Device_Type CharacterString O. Status_Flags BACnetStatusFlags R. Event_State BACnetEventState R Out_Of_Service Reliability BACnetReliability O. Out_Of_Service BOOLEAN R decouples the physical Polarity BACnetPolarity R output from the Inactive_Text CharacterString O1. Active_Text CharacterString O1 Present_Value. Change_Of_State_Time BACnetDateTime O2. Change_Of_State_Count Unsigned O2. Time_Of_State_Count_Reset BACnetDateTime O2.

10 Elapsed_Active_Time Unsigned32 O3 Properties required Time_Of_Active_Time_Reset BACnetDateTime O3. Minimum_Off_Time Unsigned32 O because Present_Value Minimum_On_Time Unsigned32 O is commandable Priority_Array BACnetPriorityArray R. Relinquish_Default BACnetBinaryPV R. Time_Delay Unsigned O4. Notification_Class Feedback_Value Unsigned BACnetBinaryPV. O4. O4. Properties required for Event_Enable BACnetEventTransitionBits O4 intrinsic reporting Acked_Transitions BACnetEventTransitionBits O4. Notify_Type BACnetNotifyType O4. Event_Time_Stamps BACnetARRAY[3] of BACnetTimeStamp O4. Profile_Name CharacterString O.