Local interconnect network (LIN) is a commonly used automotive network subsystem for a maximum of 16 nodes when a full CAN is too complex or expensive to implement. The LIN physical layer is less fault-tolerant than CAN, but it is also more deterministic, since there can only be one bus master. STM32 USARTS will often have some helpful LIN-mode functionality built into the peripheral, but an external PHY IC is still required.