Implementing automotive protocols for communication over noisy battery power lines

Summary form only given. Recently, electronics has penetrated rapidly into cars. Already electronics is 20% of the vehicle´s content. The wiring harness is´ the second heaviest component after the engine, providing power, control and communication to variety of modules. The modern car has several in-car networks, in which multiple nodes are connected by relatively few wires. The dream of a single bus that will connect every single node in the car has vanished. Already several buses and protocols are implemented in a car for power train, body electronics, entertainment and more. Implementing the automotive protocols over battery power lines reduces the amount of cables by combining power and communication over the same wire, while keeping the communication software without change and simplifies the installation of after-market modules. Power line communication in the vehicle is a technological challenge, because the battery lines are noisy and have very low impedance, which changes whenever a load is switched (lamp, air-condition). A small semiconductor device implements the technology and overcomes the hostile conditions and provides an economical solution for the automotive industry. Several carmakers are engaged in implementing these devices into their future cars. This paper presents the technical aspects of implementing multiplex communication protocols over the vehicle´s battery power lines (PLC), overcoming the severe noise profile and solving difficulties such as bit by bit arbitration.