This document summarizes a presentation about FlexRay, an automotive network communications protocol. FlexRay uses a time-triggered protocol and is designed to be faster and more reliable than CAN and TTP. It operates using a layered architecture with physical, transfer, presentation and application layers. FlexRay frames have a defined format including fields for frame ID, CRC and cycle counter. FlexRay supports both static and dynamic segments for time-division multiple access. FlexRay version 3.0 introduced improvements like single coldstart nodes and wake-up capability during operation. FlexRay is well-suited for medium data rates in applications like X-by-wire systems.

1. M. S. Ramaiah School of Advanced Studies
1
M. Sc. (Engg.) in Electronics System Design Engineering
GREESHMA S
CWB0913004 , FT-2013
8thModule Presentation
Module code : ESE2512
Module name : Data Communication and Networks
Module leader: Ms. Nireeksha
Presentation on : 14/07/2014
FlexRay

2. M. S. Ramaiah School of Advanced Studies
2
•INTRODUCTION
•FLEXRAYARCHITECTURE
•FLEXRAYFRAMEFORMAT
•COMPARISON:OVERVIEW
•FLEXRAY:ACCESSSCHEME
•FLEXRAYV2.1ANDV3.0
•FLEXRAYV3.0:TT-E
•FLEXRAY:WAKEUP
•FLEXRAY:APPLICATIONS
•FLEXRAY:ROADMAP
•CONCLUSION
Overview
•REFERENCES

3. M. S. Ramaiah School of Advanced Studies
3
Introduction
►FlexRayisanautomotivenetworkcommunicationsprotocoldevelopedbytheFlexRayConsortiumtogovernon-boardautomotivecomputing
►ItisdesignedtobefasterandmorereliablethanCANandTTP, butitisalsomoreexpensive
►VisualSimFlexRaylibraryenablesasystemdesignertoconstructmodelsofcomplexstandardandnon-standardFlexRaytopologies

4. M. S. Ramaiah School of Advanced Studies
4
Figure 1: Layered structure of FlexRay communication node
►ThePhysicallayerdefineshowsignalsareactuallyTransmitted ►Thetransferlayerisresponsiblefortiming, synchronization,messageframing,errordetectionandsignaling,andfaultconfinement ►ThepresentationLayerisconcernedwithframefilteringandmasking,framestatushandlingandcontainsthecommunicationcontrollerhostinterface ►TheApplicationLayerisauser-programmedapplicationforexpectedoperations
Layered Architecture of the FlexRay

5. M. S. Ramaiah School of Advanced Studies
5FlexRay: Architecture of Node
Figure 2 : FlexRay architecture
►MCU:Microcontroller
►CC:FlexRayCommunicationController:•embedded(e)•standalone(s)
►BD:FlexRayBusDriver
►AS:FlexRayActiveStar
►Cabling:twistedpairunshielded
►Twochannels
►Topology:busorstar

6. M. S. Ramaiah School of Advanced Studies
6
►FrameIDisaidentifier,whichis12bits,anddefinestheslotpositioninthestaticsegmentandthepriorityinthedynamicsegment
►H-CRC is a Cyclic Redundancy Check, which is 9 bits, and is calculated over the SYNC and DLC field
►NFisaNullFramefield,whichis1bit,andindicateswhetherthecorrespondingdatabufferisnotupdatedbythehostbeforesending
►CYCOisaCycleCounter,whichis6bits,andisincreasedsimultaneouslyinallnodesbythecontrolleratthestartofeachnewcommunicationcycle
Figure 3 : FlexRay frame format
FlexRay frame format

7. M. S. Ramaiah School of Advanced Studies
7
Comparison: Overview Table 1 : Comparison

8. M. S. Ramaiah School of Advanced Studies
8
FlexRay : Access Scheme ►StaticSegment:Slotswithfixedlength.Fixedassignmentbetweenslotsandnodes
Timedivisionmultipleaccess:TDMA ►DynamicSegment:Minislotswithfixedlength.Minislotscanbecombinedtocontainframeswithvariablelength.Nofixedassignedbetweenslotsandnodes ►Max.payloadperframe(staticanddynamicsegment):254bytes ►SymbolWindow:Usedforwake-upsymbols ►NetworkIdleTime(NIT):Clockcorrection
Figure 4 : FlexRay Access Scheme and flexray communication cycle example

9. M. S. Ramaiah School of Advanced Studies
9
►Coldstart/sync node: Dedicated node for startup of the FlexRay cluster + providing sync frames
►FlexRay V2.1: At least two coldstart nodes are required
►FlexRay V3.0: Single special coldstart node is allowed (TT-L node)
FlexRay V2.1 and V3.0
Figure 5 : FlexRay V2.1 and V3.0 Versions

10. M. S. Ramaiah School of Advanced Studies
10FlexRay V3.0: TT-E
►SinglegatewaynodeconnectsbothFlexRayclusters
►Gatewaynode:timegatewaysourcenode+timegatewaysinknode
►Timegatewayinterface:Clocksynchronization
►Timegatewaysinknode:TT-Lnode,i.e.,singlenodewhichdrivessynchronizationinsinkcluster
Figure 6 : FlexRay V3.0

11. M. S. Ramaiah School of Advanced Studies
11
FlexRay V3.0: TT-E
►Same cycle length in both clusters
►Fixed cycle offset between clusters
►Clusters can have different schedules
Figure 7 : FlexRay V3.0

12. M. S. Ramaiah School of Advanced Studies
12
FlexRay V3.0: Wake-up ►FlexRay V2.1: Wake-up before startup/communication only ►FlexRay V3.0: Wake-up also during operation possible: WUDOP
Figure 8 : FlexRay V3.0 : Wake-up

13. M. S. Ramaiah School of Advanced Studies
13FlexRay : Applications

14. M. S. Ramaiah School of Advanced Studies
14
FlexRay : Roadmap
Figure 9 : FlexRay Roadmap

15. M. S. Ramaiah School of Advanced Studies
15Conclusion
►FlexRay:
•Built-in time triggered: deterministic communication
•V3.0: downward compatible + interesting new features
•Best for medium data rates (~10 Mbit/s)
►CAN: •Event triggered, not deterministic•Best for low data rates (~1 Mbit/s) •Extensions available

16. M. S. Ramaiah School of Advanced Studies
16
Reference
1.Paret, D. (2012)Flexray And Its Applications. 1st edn. Hoboken, NJ: Wiley
2.Anon. (2010) available from <http://Flexray> [13 July 2014]

17. M. S. Ramaiah School of Advanced Studies
17
Thank You