LIN (Local Interconnect Network) is a low cost, serial communication system for distributed electronic systems in vehicles. It is aimed to complement existing automotive multiplex networks, such as CAN. The specification covers in addition to the definition of the protocol and the physical layer also the definition of interfaces for development tools and application software. LIN enables a cost-effective communication for smart sensors and actuators where the bandwidth and versatility of CAN is not required. The communication is based on the SCI (UART) data format, a single-master/ multiple-slave concept, a single-wire 12V bus, and a clock synchronisation for nodes without stabilised time base. The LIN consortium has been developed to standardise a concept of a serial low cost communication concept in conjunction with a development environment, that enables the car manufacturers and their suppliers to create, implement, and handle complex hierarchical multiplex systems in a very cost competitive way.
• Low cost single-wire implementation based on enhanced ISO 9141
• Speed up to 20Kbit/s (limited for EMI-reasons)
• Single Master / Multiple Slave Concept therefore no arbitration necessary
• Low cost silicon implementation based on common UART interface hardware which means that almost any microcontroller has necessary hardware on chip
• Self synchronisation in the slave nodes without crystal or ceramics resonator which leads to significant cost reduction of slave hardware
• Guaranteed latency times for signal transmission therefore predictable systems are possible
• Nodes can be added to the LIN network without requiring hardware or software changes in other slave nodes.
• The size of a LIN network is typically under 12 nodes (though not restricted to this), resulting from the small number of 64 identifier and the relatively low transmission speed.
A LIN network comprises one master node and one or more slave nodes. All nodes include a slave communication task that is split in a transmit and a receive task, while the master node includes an additional master transmit task. The communication in an active LIN network is always initiated by the master task. The master sends out a message header which comprises of the synchronisation break, the synchronisation byte, and the message identifier. Exactly one slave task is activated upon reception and filtering of the identifier and starts the transmission of the message response. The response comprises two, four, or eight data bytes and one checksum byte. The header and the response part form one message frame.