LIN bus
CAN's cheap little sibling in the car: a single-wire bus for window lifters, mirrors and seat heaters.
A consortium of carmakers including BMW, Volkswagen, Volvo and Daimler, plus Motorola, published LIN 1.0 in 1999. The reasoning was blunt: CAN is robust, but a CAN node costs money, and a mirror motor has no use for multi-master arbitration. LIN has one master that asks and up to sixteen slaves that answer, over one wire referenced to 12 V at no more than 20 kbit/s. Frames are built from ordinary UART bytes, so almost any microcontroller can speak it.
The trick that keeps it cheap is the 0x55 sync byte at the start of every frame. Slaves time its edges and adjust their own baud rate, so they can run on an internal RC oscillator instead of a crystal. Since 2016 the protocol has been standardised as ISO 17987.