An Inter-ORB Protocol for CORBA-based Embedded Systems on the CAN Bus, , , ,

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Presentation OutlineMotivationsDesign GoalsController Area Network (CAN)Design OverviewPublisher/Subscriber Protocol for CORBAEmbedded Inter-ORB Protocol (EIOP)Conclusions

Motivations (1/2)Increased Demand for Distributed Embedded SystemsDistributed Systema network of specialized micro-controllersCentralized SystemA single computer connects every peripherals. expensive point-to-point wiring limited scalability cost-effective modular extensible

Motivations (2/2)Component S/W for Distributed Embedded SystemsAll-in-one SystemComponent-based System low-level languages no OS and middleware hand-tuning mixed-up modules object-orientation platform independence extensible interfaces high reusability

Design GoalsCustomization of CORBA for Embedded NetworksCORBATarget Network: CAN (Controller Area Network)Redesign the inter-ORB protocol (IOP) of CORBASupport the group communication modelReduce resource demandsCAN-based CORBACustomization

Controller Area Network (CAN) (1/3)ISO-IS 11898 Standard for Real-time Control NetworksBounded message transfer latencyNon-destructive priority-based bus arbitrationHighly resistant to electro-magnetic interference

Controller Area Network (CAN) (2/3)Embedded Control Network (ECN)Functional Control Unit (FCU)EngineControlFCUCANAnti-LockBrakesFCUCANLightingFCUCANCANTrans-missionControlFCUCANActiveSuspen-sionFCUECN 1ECN 2

Controller Area Network (CAN) (3/3)Unique Features

Slow Serial Bus 1 Mbps bandwidth 8 bytes payloadGroup Communication n by n subject-based addressing h/w based message filtering

Design Overview

Publisher/Subscriber Protocol for CORBA (1/4)Protocol Header for CAN 2.0A

TxNode + TxPort = global port address

Publisher/Subscriber Protocol for CORBA (2/4)Conjoiner-based object binding scheme

Publisher/Subscriber Protocol for CORBA (3/4)Example Subscriber Code

Publisher/Subscriber Protocol for CORBA (4/4)Example Publisher Code

Embedded Inter-ORB Protocol (EIOP) (1/4)Compact Common Data Representation (CCDR)no alignmentno padding bytes.variable-length integerFor every 32-bit integer, saves two or three bytes.

Embedded Inter-ORB Protocol (EIOP) (2/4)Simplified Message Types of EIOPmerely two message types supportedremoved message types

location forward and connection managementLocateRequest, LocateReply, CloseConnectionand Fragment Bi-directional synchronous communicationReply and MessageError

Embedded Inter-ORB Protocol (EIOP) (3/4)Reduce the message header length of the Request type.

Embedded Inter-ORB Protocol (EIOP) (4/4)Magic is reduced into one byte.Merge GIOP_version, flags and message_types into the one-byte flags.Use integer-based identifiers for object_key and operation.Note that the resulting message fits in one CAN frame.

ConclusionsSummaryenvironment specific CORBA for embedded control networks.anonymous publisher/subscriber communication.minimized network resource demand.IDL-level compliant to the standard CORBA. Future Worksperformance number report.inter-operability with standard ORBs.