LonWorks (local operation network) is a networking platform initially designed to meet the needs of control computer programmes. A protocol developed by Echelon Corporation for networking devices serves as the foundation for the platform. Twisted pairs, power lines, and fibre optics are among the communication mediums used by Lonworks networks. They are utilised to automate numerous building-related processes, including irrigation, lighting, HVAC, controls for elevators and escalators, and security.
The LonWorks platform is comprised of the Neuron chips from various vendors, the LonTalk protocol, the various physical media used to connect devices, connectivity devices like routers and PC interface cards, network management tools, and all the various products based on the platform.
By 2010, LonWorks technology had been installed on approximately 90 million devices. The platform has been adopted as the foundation for product and service offerings by manufacturers in various industries, including building, home, street lighting, transportation, utility, and industrial automation. Despite the lack of statistics regarding the number of locations utilising LonWorks technology, it is known that products and applications built on the platform’s foundation 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, speaker control, security systems, fire detection and suppression, and newborn location monitoring and alarming, as well as remote power generation load control.
Almost all LonWorks-based devices are powered by the Neuron chip. The Neurons, which consist of multiple CPUs, communications ports, memory, firmware, an operating system, and I/Os, contain the entire LonTalk protocol stack. The Neuron chip is essentially a complete system on a chip.
There are two basic types of Neuron chips:
The Neuron Processor includes a versatile 5-pin communications port that can be set up in two ways:
In Single-Ended Mode
Data is communicated using Differential Manchester encoding.
In Special-Purpose Mode
The external transceiver encodes and decodes the data stream in this mode.
The Neuron Processor’s communications port has pins that are 5V tolerant and drive a 3.3V signal, making it possible to use any 3.3V transceiver or a 5V transceiver with TTL-compatible inputs. Twisted-pair, RF, IR, fibre-optic, and coaxial transceivers are frequently used with Neuron Processors.
Each Neuron chip has a unique 48-bit Neuron ID, which is very similar to the MAC ID used in Ethernet. To ensure individuality, Echelon manages those numbers. Using the Neuron ID, communications are started, and logical address assignments are then made for the application.
LonTalk is a control-optimised protocol. Originally created by Echelon Corporation for networking equipment over twisted-pair, powerlines, fibre optic, and RF networks. It is widely used for automating a variety of tasks in industrial control, home automation, transportation, and building systems like lighting and HVAC (see the Intelligent Building Protocol has now been accepted as a member of the ISO/IEC 14908 family of standards as an open international control networking standard). This standard, published by ISO/IEC JTC 1/SC 6, defines a multi-purpose control network protocol stack optimised for smart grids, smart buildings, and innovative city applications.
Using Standard Network Variable Types (SNVTs, pronounced “snivets”) helps ensure interoperability between LONWORKS products from various manufacturers. Echelon keeps a growing list of over 100 SNVTs for almost all physical measurement types, including variables types such as integers or floating points. For example, an SNVT for a continuous level is defined as SNVT_lev_contin.
Although Sender Authentication is used, the LonTalk protocol does not use data encryption. Despite being similar mathematically, they offer various levels of security. Data encryption is frequently used to conceal data. An example of encrypted data is you checking your account balance. To confirm that the sender of a message is an authorised sender, sender authentication is used. As an illustration, let’s look at the home utility metre. The utility would like to be able to send the metre a message containing the new pricing schedules in order to update the utility pricing rates within the metre. The metre receives the updated information, but how can it be sure that the new schedules came from an authorised source (in this case, the utility)? The utility wants to keep the information private because other home appliances can use the pricing schedules to run the house more economically. However, they do not want anyone to be able to change the pricing rates, so they employ Sender Authentication.
The utility installs a special 48-bit authentication key in the metre as part of the system’s operation. This is distinct from the 48-bit Neuron ID. The Neuron’s authentication key cannot be read or changed unless the key is already present. When the key is inserted and the utility sends the update-pricing message, the metre displays a Verified message. In response to the Verified message, the metre issues a challenge containing a 64-bit random number. The sending device receives the random number, performs an authentication transform, and returns the transform to the metre. The same transform is performed by the metre, and if it matches the utility’s response, the “update pricing” message will be processed.
In this exchange, the authentication key is never transmitted. A network spy would see the pricing schedule, then a 64-bit random number, followed by a change. Given the random number and the transform, determining the key is mathematically impossible.
Despite the fact that this authentication method is highly secure, it should be used carefully because it does cause a traffic increase for each message that is verified.
ProtoConvert’s Lonworks Gateway is a great solution to enable two way communication between a Lonworks network/device and a different protocol network like Modbus RTU, Modbus TCP, Modbus ASCii, BACnet MSTP, BACnet IP, SNMP or Metasys N2.
