Hello,

LIN (Local Interconnected Network) is a low cost serial communication intended to be used in automotive applications (windows, steering wheel, doors, mirrors, rain sensor, air conditionning, seats, ...). It's used as comfort and diagnostic communication bus.

The steering committee groups Audi AG, BMW, Daimler Chrysler, Volkswagen AG, Volvo Car Corporation. Motorola is a silicium provider.
The specifications are made by these companies and the first one was available in july 1999.

The LIN bus is a multicast master/slave bus. It can accept up to 16 ECUs (1 master, 15 slaves).
The hardware is very low-cost and based upon the UART/SCI interface and the physical layer is based upon ISO9141.
A crystal in only needed for the master. All the slaves could have a less accurate clock. This is why the LIN is cost effective.
The bus is a twisted pair, 40 meters maximum length for 12V application.
The bit rate is between 1 and 20 Kbits/s. For automotive application, the standard is 19,2Kbits/s.
A frame has 2,4 or 8 data bytes, 3 control bytes. So it takes about 5ms to transmsit a frame at 19,2 kbits/s.
The error detection is made with 8 bits checksum and a message identifier is coded with 2 parity bits. The LIN has also the sleep/wake-up capability.

Kvaser (sweden) sells some tools to design, analyse and do diagnosis on LIN bus.

I would say that the LIN bus is increasing quickly in the market. The main advantage is the low cost hardware/software. The disadvantage is that as it's a recent bus, specifications may change in the future.

I've personnaly never coded LIN bus in a 8051 microcontroller. However I've ever seen it in 68hc08 and it could be implemented in any other small 8 bits microcontroller.

Tell me if you need more informations on LIN bus.

Best regards
Stephane