The amount of electronic componentry in motor vehicles is constantly on the increase. As conventional wiring techniques with lengthy routing are no longer able to handle the quantity of data that needs to be exchanged, CAN data buses are used instead. The term Controller Area Network (CAN) refers to a serial bus system that was specially developed for use in motor vehicles. The CAN data bus serves as the basis for digital data exchange between sensors, actuators and control units, ensuring that several control units are able to process the information from one sensor and control their actuators accordingly. Quite apart from the short wiring routes, the CAN data bus has the particular advantage that, if one component fails, the rest of the system continues to work normally, greatly reducing the risk of a complete system failure. Even the older electrical systems in the vehicle are increasingly being controlled via the CAN data bus for added safety and convenience. The wireless light switch in the Golf is an example of just such a system. The driver merely has to select the lighting mode with the switch and the control unit will supply the lights with the required power. This allows convenience features such as the "coming home" function to be added. Due to the variation in the signal repetition rates and the volume of data produced, CAN data bus systems are subdivided into three categories: the drive train CAN data bus transmits the signals from control units such as the engine management unit, the transmission control and the ABS/ESP unit. The comfort CAN data bus is crucial for the climate control functions, for instance, just as the infotainment CAN data bus is for the signals received from car radios with speed-sensitive volume control.
The Local Interconnect Network (LIN) is an extension of the CAN data bus. At a maximum of 20 kbit/s, its data transfer rate is way below that of the CAN bus system. The LIN bus connects actuators or sensors with the corresponding control units. Commands are only ever transmitted in one direction, from the so-called master control unit to the downstream sensor or actuator, the “slave”. The master can transmit commands to up to 16 downstream slaves. One example of LIN bus application is the electric glass sunroof whose servomotor receives its commands from the comfort control unit via the LIN bus.
