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Lehrstuhl für Betriebssysteme RWTH Aachen University Design of a Real-Time CORBA Event Service customized for the CAN Bus Rainer Finocchiaro, Stefan Lankes,

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Presentation on theme: "Lehrstuhl für Betriebssysteme RWTH Aachen University Design of a Real-Time CORBA Event Service customized for the CAN Bus Rainer Finocchiaro, Stefan Lankes,"— Presentation transcript:

1 Lehrstuhl für Betriebssysteme RWTH Aachen University Design of a Real-Time CORBA Event Service customized for the CAN Bus Rainer Finocchiaro, Stefan Lankes, Andreas Jabs

2 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Agenda Event Service CAN Bus CEBP (Protocol for distributing Events) Benchmarks

3 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Application Example: Motor Vehicle CAN Engine Control Unit CAN Antilock Breaking System CAN Gearbox Control CAN Active Suspension CAN Lighting Control CAN Electronic Locking System CAN Electrical Seat Adjustment CAN Electrical Window Openers CAN Airbag Gateway CANCAN CANCAN Drive Control SystemPassenger Compartment Net

4 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Event Service EC Consumer Supplier... Dataflow Data Sources (Suppliers) Data Sinks (Consumers) Suppliers do not know Consumers Consumers do not know Suppliers Decoupling of Suppliers and Consumers makes system more flexible

5 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Centralized Distributed Event Service Network EC Supplier Consumer Node 1 Node 3Node 2 Centralized Event Service Event Supplier Consumer Supplier Consumer EC Node 1 Node 3Node 2 EC Distributed Event Service Event Network Supplier Consumer Supplier Consumer Supplier Consumer

6 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme The Controller Area Network Offers: Real-time Bus-Arbitration scheme with Collision Avoidance – CSMA/CA (in contrast to Ethernet with Collision Detection) Priorities for messages Broadcasting as standard addressing scheme (as opposed to point-to-point with Ethernet) But: has a very limited transfer rate of 1 Mbit/s

7 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme CAN Event Broadcast Protocol (CEBP) CEBP Protocol cares for: CAN Bus Handler EC GW Node CAN Bus EC Event Channel GW CAN Gateway Splitting of a data packet into CAN messages at the side of the sender Correct Byte-order (Little-/Big-Endian) Detection of CAN message losses CEBP Protocol works parallel to point-to-point protocol for IOP-conform CORBA communication (CANIOP) Rejoining CAN messages at the side of the receiver (Fragmentation/Reassembly) Event CAN messages Event

8 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Structure of the CAN Identifier The field Protocol is for distinguishing 4 protocols (currently: 01 2 for CEBP and 10 2 for CANIOP) Priority distinguishes 4 different priority levels Node allows for 16 transmitting nodes ECID offers 8 different Event Channels More priorities, nodes and Event Channels can be supported by CAN 2.0B (29-bit identifier) ProtocolPriorityNode ECID 2 bits 4 bits3 bits Data…

9 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Structure of CAN Message Body FP: First Packet LE: Little Endian TypeCode: 34 defined in CORBA 2.6 Data length only needed for string data types 7 of 8 Bytes used for carrying raw data TypeCode (6 bits) Byte 1Byte 2 LE Data Length / DataData… Byte 3-8 FP

10 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Priorities inside the Channel Priority Queue (Event Queue) with Delivery-Threads dynamic static Event Channel Event Queue Deliver-Threads Delivery to Consumers Events Additional decoupling between Suppliers and Consumers Supplier can continue after the Event Channel has received the Event Parallel delivery of Events to Consumers Should a Consumer need very long it does not block the other Consumers from receiving Events

11 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Priorities from End to End Real-time Event Channel + CAN Bus Priority-based delivery from end to end EC Node 1 Node 2 EC Event CAN Bus Consumer Supplier

12 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Preliminary Benchmarks Code size of the Event Service approximately 250kB (dynamically linked) Setup for latency tests: 2 Pentium II 400 MHz CAN Controller CAN/PCI/331 from ESD GmbH Benchmarks 1.Half roundtrip latency for a CORBA::Short 2.Half roundtrip latency for a CORBA::String with varying length Node 1Node 2 CAN Bus

13 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Benchmark I Transferring a CORBA::Short (2 bytes) inside one and between two nodes

14 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Benchmark II Different data sizes transferred inside one node and between two nodes

15 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Conclusions and Future Work In this talk, I have presented a CORBA Event Service, which: 1.supports asynchronous Communication between data producers and data consumers 2.is adapted to the particular features and drawbacks of the CAN Bus 3.in combination with ROFES (our RT-ORB) and the CAN Bus will allow for efficient operation in DRE-Systems 4.still needs some work concerning threading 5.needs more benchmarking and testing in general

16 WPDRTS04 – April 27, 2004Lehrstuhl für Betriebssysteme Thank you for your attention! More information about ROFES and the Event Service at:


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