LIN Bus Protocol – A Brief Overview

The Local Interconnect Network (LIN) is an embedded networking standard for connecting devices at a minimal cost, with most of its uses in the automotive industry.

It is a single-wire serial network protocol that can enable up to 19.2 Kbit/s communications across a bus length of 40 metres. The demand for a low-cost serial network increased as the technologies and facilities incorporated in the automobile developed further. This was because the CAN bus was too expensive to construct for every component in the car. Automobile manufacturers began employing several serial communication protocols, which caused compatibility issues.

In applications where the bandwidth and versatility of CAN are not required, LIN enables cost-effective communication. The common serial universal asynchronous receiver/transmitter (UART) included in most recent low-cost 8-bit microcontrollers can be used to implement LIN quite cheaply.

LIN Bus Topology and Behavior

The LIN Bus is a 16-node broadcast serial network (one master and typically up to 15 slaves).

The master initiates all messages, with at most one slave responding to a particular message identification. By answering to its own messages, the master node can likewise operate as a slave. Because all communications are initiated by the master, no collision detection is required.

Microcontrollers are commonly used as masters and slaves, but they can also be implemented in specialised hardware or ASICs to save money, space, or power.

Current applications of the LIN Bus Protocol combine the low-cost efficiency of LIN with inexpensive sensors to form tiny networks. Backbone networks can connect these subsystems (i.e. CAN in cars).

The response queue inside the LIN Bus topology contains 64 answers, one for each of the maximum 64 IDs set for LIN. This ensures that the LIN interface slave job may react to headers within the LIN specified response time.

LIN Bus Protocol Attributes:

The LIN Bus has certain features and protocols to run on. Here are some of the primary features the LIN Bus Protocol comes with:

·       A single master may have up to 16 slaves. The LIN Consortium recommends this number to ensure predictable time response.

·       After power-up, Slave Node Position Detection (SNPD) enables node address assignment.

·       Single-wire communications can reach 19.2 kbit/s at a bus length of 40 metres.

·       The LIN standard 2.2 allows for speeds of up to 20 kbit/s.

·       Latency times are guaranteed.

·       Data frame length is variable (2, 4 and 8 byte).

·       Configuration freedom.

·       Without the use of crystals or ceramic resonators, multicast reception with time synchronization is possible.

·       Error detection and data checksum.

·       Detection of faulty nodes.

·       Based on common UART/SCI hardware, there is low-cost silicon implementation.

·       Hierarchical network enabler.

·       12 V is the operating voltage.

Conclusion:

The Local Interconnect Network (LIN) protocol is based on Volcano-Lite technology created by Volvo spin-out firm Volcano Communications Technology (VCT). Since other automobile manufacturers were looking for a less expensive alternative to CAN, the LIN syndicate was formed.