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Interface DesignVehicle Busses

Omid Fatemi

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Outline

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Busses

• Computer buses

• Peripheral buses

• Instrumentation buses

• Vehicle buses

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Vehicle Buses?

• Why buses in vehicles?

– Number of electronic equipments is increasing heavily in

vehicles (expensive wiring)

– Modern vehicles control system needs a lot of

information from sensors

– Easier fault diagnostic (tester can be connected to a

single plug)

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Wire Length

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Why Multiplex Wiring?

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Classification

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General Characteristics

• Typically short buses (no hierarchy)

• Open topology to provide easy addition of new modules and removing of old modules

• Broadcast type of transmission is typically used

– (messages are sent to bus to be available for everybody)

• Immune for high noise – (temperature area -40 C to +125 C)

• Cheap price

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Protocol For Vehicle Buses

• CAN (Controller Area Network)– most European vehicle

– both classB & classC

• LIN (Local Area Network)– all vehicles in future

– classA

• VAN (Vehicle Area Network)– French vehicles (Renault, …)

– both classB & classC

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Protocol For Vehicle Buses (Con)

• ABUS

– VW

• D2B ()

– Mercedes

– classD

• TTP(Time Trigger Protocol)

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CAN Protocol

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Basic properties

• Fast (up to 1Mbps)

• Prioritization

• Configuration flexibility

• Multi master

• Multicast

• Powerful error detection

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CAN in passenger car

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CAN Implementation

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CAN node

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CANPhysical layer

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Network setup

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Twisted pair

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EMI interference

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CAN Connector

1. nc

2. CAN L

3. CAN GND

4. nc

5. CAN-shield

6. GND

7. CAN H

8. nc

9. CAN V+

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CANData link layer

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Broadcast communication

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Wired-and Mechanism

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Collision resolution

• bitwise arbitration

• CSMA/CD (carrier sense multiple access / collision detection)

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Arbitration

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Data rate

• 1 Mbps for bus length of up to 40m.

• 500 Kbps for bus length of up to 100m.

• 250 Kbps for bus length of up to 200m.

• 125 Kbps for bus length of up to 500m