FlexRayBusse

FlexRayBusse refers to a high-speed, deterministic in-vehicle network technology used to connect electronic control units in automobiles. Developed by the FlexRay Consortium and incorporated into international standards, FlexRay provides robust, time-deterministic communication suitable for safety-critical functions. The system is designed to deliver predictable latency and jitter over automotive networks.

Architecture and physical layer

FlexRay uses two independent signaling channels, designated as A and B. These channels can be used in parallel to increase bandwidth or employed for redundancy to improve fault tolerance. The physical layer typically relies on differential signaling over twisted-pair cables and supports various topologies, including linear bus configurations with star couplers. Data rates of up to 10 Mbps per channel are common, with aggregated bandwidth achievable when both channels are utilized.

Protocol and timing

The FlexRay protocol is organized into a Static Segment and an optional Dynamic Segment. The Static Segment uses time-triggered access with fixed time slots allocated to nodes, ensuring bounded latency and predictable timing for critical control messages. The Dynamic Segment allows event-driven transmissions to handle non-periodic data and burst traffic. A global time base is established through periodic synchronization frames, enabling precise coordination of clocks across devices and both channels. Network management features support fault detection, isolation, and reconfiguration to maintain operation in the presence of faults.

Applications and impact

FlexRay was designed for automotive applications requiring high determinism and reliability, including powertrain control, braking, steering, chassis systems, body electronics, and some advanced driver assistance subsystems. It often coexists with other networks such as CAN, LIN, and later Automotive Ethernet. While newer vehicle architectures increasingly favor Ethernet, FlexRay remains in use in many platforms where deterministic performance is essential.