LonWorks Tutorial

LonWorks Tutorial

by sales.aus@protoconvert.com

Understanding LonWorks Technology

LonWorks (local operation network) is a networking platform which was at first/before other things created for the needs of control computer programs. The platform is built on a protocol which is created by Echelon Corporation for networking devices. Lonworks networks use media such as twisted pair, power lines, and fiber optics for communication. It is used for the automation of different functions within buildings such as lighting, HVAC, elevator/escalator controls, irrigation, security. 
LonWorks technology includes the Neuron chips from the many vendors, the LonTalk protocol, the different physical media which connects devices, the connectivity devices such as routers and PC interface cards, network management tools, and all the different products built around the platform.


By 2010 approximately 90 million devices were installed with LonWorks technology. Manufacturers in a variety of industries including building, home, street lighting, transportation, utility, and industrial automation have adopted the platform as the basis for their product and service offerings. Statistics as to the number of locations using the LonWorks technology are scarce, but it is known that products and applications built on top of the platform include such diverse functions as embedded machine control, municipal and highway/tunnel/street lighting, heating and air conditioning systems, intelligent electricity metering, subway train control, building lighting, stadium lighting and speaker control, security systems, fire detection and suppression, and newborn location monitoring and alarming, as well as remote power generation load control.

What makes The Neuron Chip so different?

The Neuron chip is the heart of almost all LonWorks based devices. The Neurons contains the entire LonTalk protocol stack and is comprised of multiple CPUs, communications port, memory, firmware, operating system and I/Os. The Neuron chip is a complete system on a chip.

There are two basic types of Neuron chips

  • The 3120
  • The 3150
  • The 5000 is combined with inexpensive serial memory, 5000 processor provides a low cost, high-performance LONWORKS solution than those based on previous-generation Neuron 3120 and Neuron 3150 chips.

How Does the Neuron chip connect To a Network?

The Neuron Processor comes with versatile 5-pin communications port that can be configured in two ways:

1) 3.3 V Single-Ended Mode

2) 3.3 V Special- Purpose Mode.

In Single-Ended Mode

  • Pin CP0 is used for receiving serial data
  • Pin CP1 for transmitting serial data
  • Pin CP2 for enabling an external transmitter

Data is communicated using Differential Manchester encoding.

In Special-Purpose Mode

  • Pin CP0 is used for receiving serial data
  • Pin CP1 for transmitting serial data
  • Pin CP2 transmits a bit clock
  • Pin CP4 transmits a frame clock for use by an external intelligent transceiver.

In this mode, the external transceiver is responsible for encoding and decoding the data stream.

Any 3.3V transceiver or a 5V transceiver with TTL-compatible inputs can be used with the Neuron Processor because the communications port has pins that are 5V tolerant and drive a 3.3V signal. Common transceiver types that can be used with a Neuron Processor include twisted-pair, RF, IR, fiber-optic, and coaxial.

What Is The Neuron ID?

Neuron chips each have an exclusive 48-bit Neuron ID; this is almost the same as to the MAC ID in Ethernet. Echelon manages those numbers to insure individuality. Communications is instigated using the Neuron ID and then logical address assignments are made for the application.

Understanding LonTalk

LonTalk is a protocol optimized for control. Originally developed by Echelon Corporation for networking devices over media such as twisted pair, powerlines, fibre optics, and RF. It is popular for the automation of various functions in industrial control, home automation, transportation, and buildings systems such as lighting and HVAC; see Intelligent building, the protocol has now been adopted as an open international control networking standard in the ISO/IEC 14908  family of standards. Published through ISO/IEC JTC 1/SC 6, this standard specifies a multi-purpose control network protocol stack optimized for smart grid, smart building, and smart city applications.

What are SNVTs?

The use of Standard Network Variable Types (SNVTs, pronounced “snivets”) contributes to the interoperability of LONWORKS products from different manufacturers. Echelon maintains a growing list of over 100 SNVTs for nearly all physical measurement types including the type of variable such as integer or floating point. For example, a SNVT for continuous level is defined as SNVT_lev_contin.

What does LonWorks have for Security?

The LonTalk protocol does not put into use data encryption but it does implement Sender Authentication. While mathematically alike, they provide different protection. Data encryption is commonly used to hide data. Your checking account balance is an example of encrypted data. Sender Authentication is used for verifying that the sender of a message is an authorized sender. Let’s examine the home utility meter as an example. The utility would like to be able to update the utility pricing rates within the meter by sending a message to the meter with the new pricing schedules. The meter receives the new data, but how does it really know that the new schedules came from an approved source (in this case the utility)? The utility doesn’t want to hide the data, because other devices within the home can make use of the pricing schedules to more efficiently run the house. But they do not want just anyone being able to change the pricing rates so they use Sender Authentication.

The way it works is that the utility places a unique 48-bit key in the meter – an authentication key. This is not the same as the 48-bit Neuron ID. The authentication key cannot be read out of the Neuron and cannot be changed without already having the key. Once the key is in place and the utility sends the update-pricing message, the meter now sees a Verified message. The meter responds to the Verified message by sending back a challenge with a 64 bit random number. The sending device receives the random number and performs an authentication transform on it and returns the transform back to the meter. The meter performs the same transform and if it matches the response from the utility, then the “update pricing” message will be processed.

At no time is the authentication key transmitted in this exchange. A spy on the network would see the pricing schedule, followed by a 64 bit random number, followed by a change. Mathematically, given the random number and the transform, it is virtually impossible to determine the key.

While this authentication mechanism is very secure, it should be used wisely since it does double the amount of traffic for each verified message.