FlexRay

FlexRay is a high-speed deterministic automotive network technology designed to support in-vehicle data communication for distributed control systems. It was developed by a consortium that included BMW, DaimlerChrysler, Bosch, and Motorola, with the goal of delivering predictable timing and high data throughput for safety-critical applications.

The architecture centers on a dual-channel, fault-tolerant bus. Two independent physical channels (A and B) can be used in parallel, providing redundancy. FlexRay supports static (time-triggered) segments, where a fixed TDMA schedule guarantees deterministic delivery, and dynamic segments for event-driven traffic. Messages are transmitted in predefined time slots, enabling precise, predictable latency across ECUs.

The physical layer typically uses a shielded twisted-pair medium with differential signaling, and data rates can reach up to 10 Mbps per channel. Nodes synchronize to a common global time base, which is essential for the coordinated operation of the static schedule and for maintaining timing accuracy across the network. Fault tolerance is enhanced by channel redundancy and features that limit fault propagation, such as bus guardian mechanisms.

FlexRay has been applied in safety-critical automotive subsystems, including brake and chassis control, steering, and other distributed control functions, often in luxury or performance vehicles during the 2000s and 2010s. As automotive networking evolved, automotive Ethernet and other technologies have become more prevalent, reducing new FlexRay deployments, though legacy systems remain in service in some platforms.

See also: CAN, CAN FD, LIN, Automotive Ethernet, MOST.