CAN, LIN, MOST, and Bluetooth Bus Systems in Vehicles

Posted on Nov 10, 2024 in Computers

CAN Bus

Advantages

  • Avoids installing redundant sensors
  • Enables coordination and cooperation between control units
  • Provides diagnostic capabilities
  • Simplifies wiring installation (space, cost, quality)

Data Transmission

Data is transmitted via two cables regardless of the number of control units or the amount of information.

Advantages of the Data Bus

  • Extending the data protocol only requires software modification.
  • Low error rate through continuous verification.
  • Fewer sensors and signal cables.
  • Fast data transmission between control units.
  • More compact ECUs and connectors.
  • Global standard.

CAN Controller

Conditions data from the microprocessor control unit to send to the CAN transceiver.

CAN Transceiver

Transforms data from the CAN controller into electrical signals and sends them via bus cables.

Data Bus Cables

Transmit information bidirectionally (CAN-High and CAN-Low).

Data Transmission Cycle

  • Providing Data
  • Transmitting Data
  • Receiving Data
  • Reviewing Data
  • Adopting Data

LIN Bus

Assigned Functions

  • Controls data transmission speed.
  • Software defines message cycles and content.
  • Translates between LIN control units.
  • Diagnosis of slave units is performed by a master.

LIN Master ECU Features

  • Controls the LIN bus.
  • Determines message timing.
  • Commands slave units and requests information.
  • Acts as a gateway to the CAN bus system.
  • Synchronizes LIN slaves.
  • Manages Sleep-Mode.
  • Handles failures.
  • Diagnoses LIN slaves.

LIN Slave ECU Features

  • Receives, transmits, or ignores data based on message headers.
  • Can wake up the master.
  • Performs checksum verification.
  • Generates checksums for outgoing data.
  • Synchronizes with the master.
  • Exchanges data with other slaves only when requested by the master.

MOST Bus

Components

  • Optical connector for opto-conductor
  • Electrical connector
  • Internal power supply unit
  • Transmission and reception unit
  • MOST Transceiver (transmitter and receiver)
  • Standard microcontroller
  • Specific equipment components

Reasons for Implementation

  • Relatively low cost for high-speed data transmission (using LEDs and plastic optical fiber).
  • High data transmission speeds.
  • Minimized electromagnetic interference.
  • Insensitivity to electromagnetic radiation.
  • Better transmission quality/noise ratio.
  • Lightweight and smaller wiring harness.

Fiber Optic Ring Rupture

Causes of Failure

  • Ring rupture (crushed/sheared fiber or unplugged connector)
  • Power supply failure
  • Fiber aging
  • Faulty emitting or receiving diode

Diagnosing Ring Rupture

Requires installation list and diagnostic response analysis. The faulty component communicates the fault after the rupture.

Bluetooth

RF communication system developed by Ericsson.

Scope

Data exchange between mobile devices (PDAs, PCs, phones, etc.).

System Features

  • Piconet: Network of up to 8 active devices.
  • Master-Slave architecture.

Master

  • Establishes communication.
  • Sends messages.

Slave

  • Synchronizes with the master.
  • Responds to master’s data requests.
  • Active units can receive data from non-active devices.
  • Data transmission secured by 128-bit mutual recognition code.

Advantages

  • Secure connection via mutual PIN.
  • Short range (up to 10m) at 2.45 GHz enhances safety.
  • Small and compact modules (2-3 cm²).

Component Description and Operation

Control Module

  • Divides data into short packets (625µs).
  • Calculates 16-bit checksum.
  • Detects transmission failures automatically.
  • Transmits voice using digital signals.

Radio Module

  • Implements frequency hopping (approx. 1,600 times per second).