The permanently increasing number of convenience and safety
functions leads to higher complexity of in-car electronics and the
rapidly growing amount of sensors, actuators and electronic control
units places higher demands on high- speed data communication
protocols. Safety-critical systems need deterministic protocols
with fault-tolerant behavior. The need for on-board diagnosis calls
for flexible use of bandwidth and an ever-increasing number of
functions necessitates a flexible means of extending the
system.
None of the communication solutions available on the market
until now (like CAN or TTP) have been able to fulfill all these
demands. To solve these problems, BMW together with several
semiconductor companies has developed a new protocol for
safety-critical applications in automotive vehicles.
The byteflight protocol combines the advantages of the familiar
synchronous and asynchronous protocols and guarantees high data
integrity at a data rate of 10 Mbps and an information update rate
of 250 μs. Additional characteristics are collision-free bus
access, guaranteed latency for a certain number of high- priority
messages, high flexibility, easy system extension, dynamic use of
bandwidth and low system costs.
In order to reduce EMI, a physical layer solution using optical
transmission was developed. In a star net configuration with an
intelligent star coupler, communication is bidirectional on a
single plastic optical fiber. The transceiver chip, the
light-emitting diode and the photodiode are integrated into the
optical connector.
Silicon for byteflight controllers, an intelligent star coupler
and physical layer transceiver as well as several development tools
are available. The first application in high-volume automobile
production will start within the next year and will include
passive-safety and body functions.