Auto Electronics

FlexRay promises major long-term benefits

After several years of hard work by industry leaders worldwide on the development of the FlexRay communications protocol, the initial automotive applications are starting to become visible on the horizon. The first FlexRay IP-equipped components — including a FlexRay controller application-specific standard IC from Fujitsu — are in the market, with development kits that enable designers to start work. It's too early to predict when the first vehicles incorporating FlexRay will move into production. But, when that occurs, the transition will mark a major shift forward for the automotive industry worldwide.

FlexRay delivers the speed and reliability required for next-generation in-car control systems. FlexRay enables the replacement of mechanical and hydraulic systems with electronic systems that are more reliable and less expensive. This shift became necessary when leading automakers found that the existing protocols, including the successful and popular control area network (CAN), were running out of gas. This is occurring in part because of the increasing numbers of electronic systems in vehicles, numbers that have been expanding steadily through several design cycles. As more sensors, actuators and controllers are designed into cars, the amount and quality of data required to manage them increase significantly. The demand for higher data rates, fault-tolerant implementations, and deterministic performance has outrun CAN, which provides a maximum data transfer rate of 1 Mbps.

FlexRay is the perfect backbone bus system to move beyond CAN. FlexRay supports communication speeds up to 10 Mbps per channel, which is at least 10 times faster, and as much as 40 times faster than CAN, depending on configuration. FlexRay also increases the frame length to 254 bytes from the eight bytes per frame provided by CAN.

FlexRay uses a time-triggered protocol. Time triggering enables accurate data transfers according to a predefined schedule.

In addition, FlexRay allows data to be available on a redundant communication system that enables a fully duplicative network configuration, a vital element in assuring high levels of system reliability. FlexRay is flexible, so it can be tuned for availability of bandwidth or for dynamic allocation of bandwidth, which can optimize throughput. And, FlexRay is versatile, with the ability to support various topologies including bus, star and hybrid configurations.

Both synchronous and asynchronous data transfer are allowed with FlexRay, which guarantees frame latency and jitter during synchronous data transfer, and prioritizes messages during asynchronous transfer. Using a global time base, FlexRay provides fault-tolerant clock synchronization, and contains errors in the physical layer by using an independent bus-guardian mechanism.

FlexRay's clock-synchronization scheme is innovative, because it can compensate for differences in quartz clocks that run on the network, as well as for any minor changes in clock frequencies. The clock synchronization is a distributed mechanism with no master timekeeper, so if a node fails or is taken off the network, the other nodes will continue to operate.

These are significant features, demonstrating FlexRay's long-term potential to help convert older engine-control, safety and comfort systems to electronics systems. The initial FlexRay applications will likely appear in the automotive chassis and powertrain systems, where fast, reliable electromagnets will replace mechanical camshafts for valve control. But these first systems are just the beginning. After those will come vehicle applications for engine control, body control, passenger safety and comfort. Over the longer term, FlexRay creates the potential for complete X-by-wire systems, including drive-by-wire.

After several years of refinement, the FlexRay standard is ready for system developers to leverage in next-generation vehicles. Support for the FlexRay standard from the automotive electronics suppliers is vital in its advancement, and provides an example of the progress made possible when the industry collaborates on standards implementation. Fujitsu is supporting these efforts with a development system and a microcontroller containing FlexRay IP. This collaboration also offers global automotive OEMs a corollary benefit: it frees their own development resources to be used on features that differentiate their vehicle products, based on customer interests and requirements.




ABOUT THE AUTHOR

Keith Horn is senior vice president of sales and marketing of Fujitsu Microelectronics America Inc., Sunnyvale, Calif.

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