LIN Bus, Local Interconnect Network
- the Local Interconnect Network, often referred to as the LIN Bus is used in many automotive and similar applications to connect remote nodes to a central controller using a single wire.
The LIN Bus or more correctly the Local Interconnect Network is a serial networking system used for communication between components in automotive applications and vehicles.
The development of the LIN Bus arose out of the need for a cheap serial network in automobiles as the number of items within a vehicle that needed to sense conditions or requiring control increased. An earlier system called the CAN bus was too expensive to implement for every component in the car. As a result European car manufacturers started using different serial communication topologies, and this led to compatibility problems. The LIN Bus aimed to reduce costs and thereby enable a single system to be used across the industry and hence fewer compatibility issues.
In order to have a bus system that was applicable to many manufacturers and could be used for components across the industry without compatibility issues, a consortium of manufacturers was set up. This defined the LIN Bus, Local Interconnect Network and ensured it could be moved forwards.
The LIN Consortium was set up in the late 1990s by five European automakers including BMW, Volkswagen Audi Group, Volvo Cars, Mercedes-Benz as well as Volcano Automotive Group and Freescale.
It took until November 2002 before the first fully implemented version of the new LIN specification was published LIN version 1.3. Then in September 2003 LIN version 2.0 was introduced. This expanded the overall capabilities of the LIN Bus and it also made provisions for significant additional diagnostics features and tool interfaces.
LIN Bus applications
The Local Interconnect Network, LIN Bus has many possible applications within an automobile. Some of the areas where LIN Bus connectivity may be required include:
- Roof area
- Rain sensor - possibly interrogated every 10 - 20 ms
- Light sensor
- Light control
- Sun roof
- Door / window
- Window control
- Door lock
- Steering wheel
- Cruise control
- Mobile phone
- Seat position control
- Occupancy sensor
- Heating control (if installed)
These applications give only a small selection of the possible applications for which the LIN Bus can be used. Not only are there the obvious applications, but there are a huge additional number that is contained within other areas of the vehicle that may not be immediately obvious.
LIN Local Interconnect Network basics
The LIN Bus has a number of key features that are central to the development of the system and also the LIN standard as well.:
- Low cost single-wire implementation based on an enhanced version of ISO 9141)
- Speed up to 20Kbit/s - suitable for most control and monitoring applications but limited for EMI / EMC reasons.
- Single Master / Multiple Slave Concept simplifies operation.
- No arbitration necessary for effective and simple operation.
- Low cost silicon implementation to reduce manufacturing costs. The LIN Bus is based on common UART/SCI interface hardware.
- Almost any Microcontroller has necessary hardware on chip.
- Self synchronization. It does not need a crystal or ceramics resonator in the slave nodes.
- Guaranteed latency times for signal transmission to give reliable and predictable responses.
The LIN Bus or Local Interconnect Network is being used increasingly in many automotive applications. As electronics is used more widely within automobiles, so the use of the LIN Bus increases.
By Ian Poole
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