HAL and Implementation
Many car subsystems interconnect with each other and the in-vehicle infotainment (IVI) system via various bus topologies. The exact bus type and protocols vary widely between manufacturers (and even between different vehicle models of the same brand); examples include Controller Area Network (CAN) bus, Local Interconnect Network (LIN) bus, Media Oriented Systems Transport (MOST), as well as automotive-grade Ethernet and TCP/IP networks such as BroadR-Reach.
The Android Automotive hardware abstraction layer (HAL) provides a consistent interface to the Android framework regardless of physical transport layer. This vehicle HAL is the interface for developing Android Automotive implementations.