Vehicle networks: where CAN, LIN and Ethernet belong
The networks used inside a vehicle are divided by speed, cost and real-time needs. The area each one covers and the role of the gateway.
| Network | Speed | Where used |
|---|---|---|
| LIN | Up to 20 kbps | Windows, mirrors, seats, switches |
| CAN | Up to 1 Mbps | Most of powertrain, chassis and body |
| CAN FD | 2 to 8 Mbps in the data phase | Recent ECUs, diagnostics and updates |
| FlexRay | 10 Mbps, time-division | Some premium chassis systems (in decline) |
| Automotive Ethernet (100/1000BASE-T1) | 100 Mbps and up | Cameras, ADAS, central computer, zonal backbone |
Gateway
It joins several networks, passes on only the messages that are needed, and protects the internal networks from the outside (diagnostic port, telematics). It is also the first gate against security attacks.
Communication design documents
Vehicle communication is defined in a DBC file (definitions of CAN messages and signals: ID, period, bit position, scaling) or in ARXML. For example, "12 bits from byte 3 of message 0x123, in units of 0.1 km/h, at a 10 ms period = vehicle speed". The send and receive code is generated from these definitions.
Tools
Tools such as Vector CANoe/CANalyzer, PCAN and BUSMASTER monitor the bus and, with the DBC loaded, show values signal by signal. For a hobby project, a USB-CAN adapter with python-can and cantools does the same job.