FlexRay – a first glance by EB Automotive

FlexRay – a first glance by EB Automotive


flex pay our first glance in the past few years several communication protocols for automotive applications have been developed the can protocol has been developed by Bosch and is nowadays utilized by almost every car manufacturer it supports data rates of up to one megabit per second the linden protocol has been developed for less demanding applications in terms of communication speed and latency in contrary the most bus satisfies the high data rates needed for multimedia applications finally flex ray has been especially developed by the Flex raid consortium since 2004 safety related applications in the automotive industry today flex ray is applied in real-time applications and as a replacement of can when higher data rates are required flex ray has been developed to support X by wire applications such as steer-by-wire or break by wire these are replacements of the traditional mechanical and hydraulic control systems through electronic control systems flex rave features two communication channels each with a data rate of 10 megabits per second and payloads of frames up to 250 4 bytes furthermore the communication is time triggered in contrast to the event triggered can protocol this is why flex rate guarantees fixed communication latencies and a global synchronous time basis for all participating electronic control units a flex register consists of several nodes and two communication channels channel a and channel B in order to provide reliable communication a node must be connected to both communication channels to reduce cost using only one channel can be sufficient flex ray supports both bus and star topologies to increase the communication distance between two nodes they have to be connected via star couplers the communication scheme of a flexural Uster is built up of communication cycles that are repeated over and over again from startup of the network until it is shut down a communication cycle consists of the network communication time and the network idle time the communication time includes a mandatory static segment an optional dynamic segment and the symbol window in the static segment deterministic communication ensures constant latency flex ray adheres to a time division multiple access method which means that there are equally sized slots and that the point of time is fixed when the frame is transmitted on the channel in the dynamic segment event-driven communication takes place this is usually used for low priority data for example for the transmission of diagnosis information let’s have a look at an example scenario with several nodes the nodes a B and C have their own exclusive slot in the static segment for transmission note that all the frames in a static segment have the same length the communication in the dynamic segment is event based and if a controller sends a message its mini slot expands to the actual duration of transmission in contrary to the frames of the static segment frames in dynamic segments can have different sizes if there is no message to be sent the mini slot elapses unused last but not least let’s have a look at an electronic control unit software application is executed on a host processor which is connected to a dedicated communication controller that executes the Flex ray protocol the translation from digital signals of the communication controller to analog signals on the bus is accomplished by the bus driver if you’d like to find out more about our flex rate products watch our follow-up videos you


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