LonWorks PLC

(c) 2013 R. Newman

University of Florida

What is LonWorks Protocol• Multiple medium protocol for home automation

(domotics) and control• Local Operating Network (LON)• Narrowband PLC, TP, CX, fiber optics, RF

– TP 78 kbps using Differential Manchester– PLC 5.4 or 3.6 kbps depending on frequency band

• Developed by Echelon Corp.– 60 million devices by 2006

• Multiple standards– International and open industry standard– European standards– China national standards

LonWorks Standards• International and open industry standard

– Submitted to ANSI 1999 - ANSI/CEA-709.1 – Basis for IEEE 1473-L (in-train controls)– SEMI (semiconductor equipment manufacturing)– One of several data link/physical layers of the BACnet ASHRAE/ANSI

standard for building automation.– ISO and IEC standards ISO/IEC 14908-1, -2, -3, and -4

(communications protocol, twisted pair signaling technology, power line signaling technology, and Internet Protocol (IP) compatibility)

• European standards– AAR electro-pneumatic braking systems for freight trains– IFSF (European petrol station control)– EN 14908 (European building automation standard)– Part of Household Appliances Control and Monitoring – Application

Interworking Specification (AIS) standards of CECED (European Committee of Domestic Equipment Manufacturers)

• China national standards– Controls standard, GB/Z 20177.1-2006 – Building and intelligent community standard, GB/T 20299.4-2006

LonWorks Major Elements• LonTalk protocol

• Neuron chips

• LonWorks transceivers

• Network management/applications

• SNVTs (Standard Network Variable Types)

LonTalk Protocol• Media

– Twisted pair, powerline, radio frequency, fiber optics, coaxial cable

– Highest data rate 1.2 Mbps• Reliability

– Supports end-to-end acks with ARQ– Broadcast acks also

• Medium access– Proprietary collision prediction algorithm– Collision detection on some media (e.g., TP)– Optional priority feature

• Network management/applications• SNVTs

ACK implosion problem!

LonTalk Addressing• Hierarchical

– Domain, subnet, node; also Group– All nodes in domain, subnet addressable

• Channel = physical medium• Domain = logical set of nodes on one or more

channels• Communication only possible in domain• Multiple domains may share channel(s)• Subnet – must share a channel

– cannot span a router, 127 node max– Domain may have up to 255 subnets

• Group – may use multiple channels– Node may be in up to 15 groups, <64 nodes/group– Domain may have up to 255 groups

LonTalk Delivery Services• Unacknowledged

– Most commonly used– Widest bandwidth

• Unacknowledged/Repeated– No acks, but multiple copies sent per settings

• Acknowledged– Used when reliability required– Timeout set at installation time

• Priority– Time slots may be set aside for priority traffic– Used sparingly – reduces bandwidth available

LonTalk Network Management• All nodes are network management capable• Find unconfigured nodes and download network

addresses. • Stop, start and reset node applications • Configure routers and bridges • Download new application programs • Change the network variable configuration table:

– type of protocol service used to send the network variable

– whether the variable is sent in a priority slot.

LonWorks Transceivers• Twisted Pair

– 78 Kbps/4600 ft (1400 m)– 1.25 Mbps/430 ft (130 m)

• Powerline– Spread spectrum (proprietary) or narrowband– 10 Kbps, Up to 2000 m on clear line

• Radio Frequency– 400-470 MHz licensed– 900 MHz unlicensed

• Configuration– Installation announces device’s presence– Binding network variable tells device what data to

share with whom

Longer distance => more attenuation=> lower SNR (noise is constant)=> lower data rate (Shannon's Thm)

LonWorks Datalink Layer• Error Detection (CRC)

• Flexible allocation of bandwidth

• Priority access mechanisms

• Graceful behavior under overload – p-persistent CSMA

• Message collision avoidance

• Optional collision resolution, collision detection

CSMA: When current transmission donep-persistence: Tx with prob. pOptimal p is 1/N for N contenders

CD not possible on RF or PLC medium=> Collision avoidance important

LonWorks Network Layer• Node address information

• Message routing to segment – determining which nodes on the network

receive various messages

• Network bandwidth usage control

• Routers – segment traffic – communicate between different channels

LonWorks Transport Layer• Broadcast addressing

• Unicast addressing

• Multicast addressing - groups

• Repeated service

• Acknowledged service

• Unacknowledged service

• Duplicate packet detection

• Authentication

LonWorks Session Layer• Acknowledgment of received message

• Application-to-application communication

• Retry if the correct response is not received from the remote node

• Request to a destination group and receive individual responses from the group

• Request - response message authentication

LonWorks Presentation Layer• Input, output, and configuration variables

for the node

• Standard data representations for physical quantities

• Network variable description

LonWorks Application Layer• Memory storage for application program

• Built-in real-time operating system

• Device drivers for the I/O hardware on the Neuron Chip

• Standard Network Variable Types (SNVTs)

SNVTs• Standard Network Variable Types

• A key to interoperability

• Standardizes variables used to name and describe things and their states

• Maintained by LonMark International

• Each standard known as an SNVT– Pronounced “snivit”– E.g., temperature is a 16-bit quantity

representing -274 to 6279.5 Celcius

SNVT ExamplesVariable Type UnitsTemperature Degrees CelsiusReal Time MM,DD,YYYYEvent Count Counts% of Full Scale PercentVolume Gallons, CCF, litersFlow Gal or liters/hourWeight Kilograms, Lbs.Speed Miles or Km/hourAlphanumeric ASCII CharactersAlphanumeric Kanji Characters

Variable Type UnitsSwitch State BooleanDevice State BooleanEnergy Kilowatt-HoursPower WattsVoltage DC or AC RMSCurrent Amps AC, RMSResistance OhmsSound Level dBrncVoltage dB microvolts

Alphanumeric International charactersDay of Week Enumerated List (Mon-Sun)Elapsed Time Second, Milliseconds, Days or HoursPhone State Enumerated List (On-hook, off-hook, busy, ringing, etc.)PressureLbs./sq.in, Pascals, Inches-HgRelative Humidity Percent

LonWorks Links

• http://www.ieclon.com/LonWorks/LonWorksTutorial.html