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AutoPi > Blog > LIN Bus Protocol: The Ultimate Guide (2022)

LIN Bus Protocol: The Ultimate Guide (2022)

Authored by autopi 18 Mar, 2021

— LIN Bus protocol - It is a supplement to CAN Bus, offering lower reliability and performance, but also lower costs. It is commonly used for windows, wipers etc.

LIN Bus Protocol: The Ultimate Guide (2022)

LIN Bus stands for Local Interconnect Network Bus and it is basically a cheaper supplement to CAN Bus, providing lower reliability and performance. It is a very common network and is increasing in its popularity.

Once again, we have prepared a simple introduction to LIN Bus. Several topics and aspects have been researched, analyzed and then included, all with the purpose of explaining the LIN Bus and LIN Protocol to you, in a very easy and understandable way.

We have combined expertise from our top tech engineers and wrote this article in a very simple way, in order to make it as easy to understand as possible.


What is a LIN Bus?

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

LIN Bus protocol is very cost effective, meaning it is much cheaper than CAN Bus. On the other side, it also offers much 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. Instead, LIN Bus was released to solve this challenge and has worked out perfectly ever since.

LIN Bus Banner


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.

Two bus states, sleep mode and active are used within the LIN protocol.

Key facts about LIN Bus

  • Low cost option.

  • Single wire with 1-20 kbit/s at maximum 40m bus length (+ground).

  • Operating voltage - 12V.

  • Frequently used in vehicles for wipers, air condition, steering wheel, windows and so on.

  • LIN clusters contain of 1 master and up to 16 nodes.

  • Latest vehicles have more than 10 nodes.

  • Several data lengths (2,4 and 8 bytes).

  • Guaranteed latency time with time triggered scheduling.

  • Sleep mode and wake up support.

  • The physical layer is based on ISO 9141 - K-line.

  • LIN Bus protocol support error detection and configuration.


How Does the LIN Bus Work?

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

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

  • Sensors for position and temperature.

  • Speed and pressure.

  • Cruise control.

  • Wipers.

  • Radio.

  • Climate control.

  • Small motors.

  • Side mirrors.

  • Seat control.

  • Locks.

  • Rain sensors.

  • Headlights.

  • And more.

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.


lin bus and can bus

Lin Bus interface

  • Lower cost.

  • Latency time - more predictable network.

  • Overall implementation - simpler to implement than CAN.

  • Typically, a LIN master works as a gateway to the CAN Bus.

  • LIN clusters have a single master.

  • LIN is settled - not event driven.

  • Uses single wire 12V.

  • LIN offers max 20 kbit/s.


CAN Bus interface

  • Uses twisted shielded dual wires 5V.

  • Uses 11 or 29 bit identifiers.

  • Very complex and robust interface.

  • CAN could have multiple masters.

  • CAN offers up to 1 Mbit/s.

differences between LIN bus and can bus


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.

LIN Bus frame explained in an easy picture


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 Description File (LDF)

The LIN network is described by a LIN description file (LDF) that includes information about frames and signals. The file is being used for creation of the software in both master and slave.

You might need to decode your raw LIN bus data to physical values as a part of your LIN data workflow.

In order to decode raw data into a readable form, you need to extract LIN signals from the LIN frame payload. LIN bus decoding is very similar to CAN bus decoding and it requires the same information.


LIN Bus History

Here, you can find the history of LIN Bus. We have also created a timeline of the LIN Bus history, in order to make it easier and more understandable.

  • 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


Timeline showing the history of LIN bus


Future of LIN Bus

LIN Bus is expected to be commonly used in modern vehicles due to its low cost feature expansion.

We have seen a huge increase in popularity of LIN Bus since 2015 and it is expected to increase even more.

We have also heard that LIN Bus might be also used in J1939 for its low cost. However, a lot will change and we hope you will follow it with us.

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