LIN Bus Protocol: The Ultimate Guide (2023)

What is a LIN Bus?

LIN Bus stands for Local Interconnect Network (LIN) and is used for communication among components in the vehicle. It is also known as a supplement to CAN Bus.

LIN protocol is very cost effective and much cheaper than CAN Bus. However, it offers a lower performance and is not as reliable as CAN Bus.

LIN Bus came to life when CAN Bus was simply too expensive to implement for every component in the vehicle. Alternatively, LIN Bus was released to solve this challenge and has worked out perfectly.

What is a LIN protocol?

LIN protocol is a wired communication protocol for electronic devices. It consists of one master and one or more slaves.

Each LIN frame consists of two pairs - header and response. The header is always sent by the LIN master and the response is sent by either one dedicated LIN slave or the LIN master.

Furthermore, Lin protocol uses two bus states, a sleep mode and a active mode.

How Does the LIN Bus Work?

LIN Bus can be also used in the vehicle’s battery power-line, with a LIN over DC (DC-LIN) transceiver, and is standardized as ISO/AWI 17987-8.

Nowadays, LIN Bus is pretty much standardized in all modern vehicles. There are several cases, where LIN Bus is being used such as:

In addition, LIN Bus is also being used in home appliances such as: washing machine, stove, refrigerator and more. The forecast shows the increase in demand for LIN Bus and its applications. Electronic control unit is one of the common applications among many others.

LIN Bus vs CAN Bus

See the differences between LIN Bus interface and CAN Bus interface below. We have mentioned their key differences as well as their key benefits.

The LIN Frame Format

Simply said, the LIN Bus message frame consists of a header and a response. Generally speaking, the LIN master typically sends a header to the LIN bus, which then triggers a slave.

The slave sends up to 8 data bytes in response. An illustration of the LIN frame format can be seen below.

We will now explain to you in details specific parts of the LIN frame format.

Break

• The Sync Break Field (SBF), also known as just Break is a minimum of 13 + 1 bits long.

• Commonly used as 18 + 2 bits.

• Operates as a start of the frame.

Sync

• Is 8 bit long.

• Has a predetermined value of 0x55.

• Its structure allows the LIN nodes to determine the time between rising and/or falling edges.

Identifier

• Is 6 bits long and followed by 2 parity bits.

• The ID operates as an identifier for each LIN message.

• Slaves determine the validity of the ID field and operate accordingly - ignore the subsequent data transmission, listen to the data transmitted from another node and publish data in response to the header

In addition, usually one slave is taken for the information at the time. This means that there is zero collision risk and no need for arbitration. The 6 bits allow for 64 IDs, where ID 60-61 are used for diagnostics.

LIN Bus Message Frames

A LIN message consists of identifier byte, checksum byte, synchronization byte and synchronization fields.

Frame types

• Unconditional frame - 0-59 ID dec, 00-3B ID hex.

• Event-triggered frame - 0-59 ID dec, 00-3B ID hex.

• Sporadic frame - 0-59 ID dec, 00-3B ID hex.

• Diagnostic frame - 60-61 ID dec, 3C-3D ID hex.

• User-defined frame - 62 ID dec, 3E ID hex.

• Reserved frame - 63 ID dec, 3F ID hex.

LIN Bus History

In order to make LIN Bus more understandable, we created a timeline of LIN Bus' history.

• 1999 - LIN 1.0 released by the LIN Consortium (BMW, Volkswagen Group, Volvo Cars, Audi and Mercedes-Benz)

• 2000 - The LIN Bus protocol was updated - LIN 1.1 and LIN 2.2

• 2002 - LIN 1.3 was released

• 2003 - LIN 2.0 was released with multiple changes

• 2006 - LIN 2.1 specification released

• 2010 - LIN 2.2A was released

• 2010 - 2012 - Based on LIN 2.0, SAE standardized LIN as SAE J2602

• 2016 - LIN standardized as ISO 17987:2016