FlexRay basics
In recent years there has been a significant increase in the amount of electronics that have been introduced into the car, and this trend is expected to continue as car manufacturers introduce further advances in safety, reliability and comfort. The introduction of advanced control systems combining multiple sensors, actuators and electronic control units are beginning to place demands on the communication technology that were not previously addressed by existing communication protocols. Additional requirements for future in-car control applications include the combination of higher data rates, deterministic behavior and the support of fault tolerance.Flexibility in both bandwidth and system extension will also be key attributes as the need for increased functionality and on-board diagnostics also increase. Availability, reliability and data bandwidth are the key for targeted applications in Powertrain, Chassis and Body control, and these must also be supported within the automotive environment which presents some unique challenges. The core member companies of the FlexRay Consortium (BMW, Bosch, DaimlerChrysler, Freescale, GM, NXP Semiconductors and Volkswagen) have been working together in developing the requirements for an advanced communication system for future automotive applications. These seven companies have brought together their respective areas of expertise to define a communication system that is targeted to support the needs of future in-car control applications.FlexRay is a communication system that will support the needs of future in-car control applications. At the core of the FlexRay system is the FlexRay communications protocol. The protocol provides flexibility and determinism by combining a scalable static and dynamic message transmission, incorporating the advantages of familiar synchronous and asynchronous protocols. The protocol also supports:
Fault-tolerant clock synchronization via a global time base
Collision-free bus access
Guaranteed message latency
Message oriented addressing via identifiers
Scalable system fault-tolerance via the support of either single or dual channels A physical layer incorporating an independent Bus Guardian provides further support for error containment. The FlexRay system is targeted to support a data rate of 10Mbit/sec with increased flexibility for easy system extension and the dynamic use of bandwidth. The 10Mbit/sec data rate is available on two channels, giving a gross data rate of up to 20Mbit/sec. In support of FlexRay, an array of development tools for design, measurement and simulation of the communication system is available on the market. FlexRay is targeted at meeting the needs of present and future in-car control applications and the aim is to establish FlexRay as the de facto standard in the automotive industry.
