LIN Bus: Still going strong

May 21, 2015 // By Anirban Sengupta, Sivaguru Noopuran, Cypress Semiconductor
In the 1930s when Galvin Manufacturing Corp. (today’s Motorola) introduced the fitted car radio, few could imagine what the future looked like. For years the only electronic component in a car was the radio. The infotainment system in today’s automobile is just one of the many systems that are electrically controlled: the Number of Electronic Control Units (ECU) in a modern car today can be as high as 80. No wonder the market for automotive electronic components has been on the rise and is expected to hit $18.5B by 2018.

In the initial years, the practice was to have standalone autonomous electronic systems. The need for a mechanism to enable systems to communicate with each other was becoming more significant. This lead to the introduction of networks such as serial communication channels (bus) that would co-ordinate the individual electrical systems and lead to improved functionality of the vehicle as a whole.

Fig. 1: The electronic landscape of toda's passenger vehicles contains up to 80 control units

In 1983, Bosch began developing the CAN (Controller Area Network) bus and officially released the protocol in 1986. Even today, when different vehicle bus standards are available, CAN continues to be the most popular. In a CAN network, all the nodes (originating from different ECUs) act as master and are not assigned specific addresses.

Multiple nodes may transmit data to the CAN-bus, the message identifier then helps determine the priority of the messages. The highest priority message will pull the CAN bus to the dominant state and all the other nodes stop transmitting. The nodes are in fact transceivers and, based on specific functions, they may look out for specific messages from the bus apart from transmitting messages. Thus, information flow happens between different nodes connected to a CAN bus.

CAN is highly reliable because of multiple error checks that are made, such as stuffing errors, bit errors, checksum errors, frame errors, and acknowledgment errors. In terms of data-rate, CAN supports up to 1MB/s. Thus CAN is the default choice for connecting critical function ECUs in vehicles (e.g., Gear box, Temp Sensor etc.).

However, the role of electronics in automobiles is not limited to these critical units only. Over the years, the market for automotive body electronics has been increasing. Examples range from seats, windows, smart wipers and climate control sensors.. For body electronics, the key requirement is to ensure improved comfort and safety of the vehicle. These are systems that may not

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