LIN Bus
LIN BusApril 5, 2000. . . BMW AG, several other car manufacturers, the communications specialist Volcano Communications Technologies AB, and the semiconductor manufacturer Motorola announced the formation of an industry consortium with the objective to define and implement an open standard for class-A serial buses in vehicle networks. The standard has been named Local Interconnect Network (LIN) and will be the enabling factor for the implementation of a hierarchical vehicle network in order to gain further quality enhancement and cost reduction of vehicles.
The standardization will reduce the manifold of existing low-end multiplex solutions and will cut the cost of development, production, service, and logistics in vehicle electronics.
Typical applications for the LIN bus are assembly units such as doors, steering wheel,
seats, climate regulation, lighting, rain sensor, or alternator.
In these units the cost sensitive nature of LIN enables the introduction of mechatronic elements such as smart sensors, actuators, or illumination. They can be easily connected to the car network and become accessible to all types of diagnostics and services. The commonly used analog coding of signals will be replaced by digital signals, leading to an optimized wiring harness.
The increasing software complexity of today's distributed electrical systems represents a major challenge for car manufacturers in terms of design, implementation and maintenance of these systems during the lifecycle of a car project. Provision for highly automated tools addressing the needs of this process are essential in order to ensure efficiency, high quality and short lead-times.
For this very reason - as an industry first - the LIN specification covers not only the protocol definition itself, but also the standardization of tool and application programming interfaces.
The introduction of LIN is accompanied by a holistic chain of tools supporting the car manufacturer in all phases of the development project.
The goal of LIN is to define a communication standard below the level of CAN - the major standard in vehicle networking. With respect to cost and performance, LIN is complementing CAN but not competing with it. LIN targets low end applications where the communication cost per node must be two to three times lower when compared to CAN and where the performance, bandwidth, and complexity of CAN is not required.
The communication protocol is based on the common serial ISO 9141 NRZ transmission. It is a single-master/multiple secondary protocol, transmitted via a single-wire bus powered by the 12V car battery. The concept of message identification allows a multi-cast data transmission between any network node controlled by the master. A particular feature of LIN is the incorporation of a synchronization mechanism for slave nodes so that - unlike CAN - a crystal resonator is not required.
This enables the application of true single-chip solutions for low cost mechatronics. The LIN standard includes the specification of the transmission protocol, the transmission medium, the interface between development tools, and the interfaces for software programming.
LIN guarantees the interoperability of network nodes from the viewpoint of hardware and software, and a predictable EMC behavior. It is not exclusively defined for automotive applications and is expected to be also successfully applied to industrial or whitegood electronics. A wide portfolio of semiconductor and software products is already available for first LIN implementations:
The LIN Bus is a standardized, serial single wire bus transferring data at a speed of 19.2 kBd. (Some LIN Busses may operate at slightly different speeds.)
The LIN Bus is very similiar to the M-Bus normally found on climate control systems.The LIN Bus (Busses) are diagnosible with the DISplus.
Vehicles may have more than one LIN Bus that are not interconnected (i.e. mirror system bus, AHL motor control bus, etc.).