An article on automotive-grade CAN bus communication technology

Individual control system: An electronic control system in which an electronic control unit (ECU) controls a working device or system, such as an engine control system, automatic transmission, etc.

Centralized control system: An electronic control system in which one electronic control unit (ECU) controls multiple working devices or systems at the same time, such as the chassis control system of an automobile.

Controller Area Network System (CAN Bus System): Multiple electronic control units (ECUs) simultaneously control multiple working devices or systems, and the common information of each control unit (ECU) is transmitted to each other through the bus.

In the dominant state, the voltage on the CAN-High line will increase by a predetermined value (for the CAN driver data bus, this value is at least 1V), and the voltage on the CAN-Low line will decrease by the same value (for the CAN driver data bus, this value is at least 1V).

Therefore, on the CAN drive data bus, the CAN-High line is in an activated state, and its voltage is not less than 3.5 (2.5V+1V=3.5V), while the voltage value on the CAN-Low line can drop to a maximum of 1.5V (2.5V-1V=1.5V).

In the recessive state, the voltage difference between the CAN-High line and the CAN-Low line is 0V, and in the dominant state, the minimum difference is 2V.

Total system

The three systems are networked via a gateway. Due to the different voltage levels and resistor configurations, it is not possible to couple the CAN drive data bus and the CAN comfort/infot ai nment data bus . In addition, the transmission rates of the two data buses are different, which means that they cannot use the same signal .

This requires a conversion between the two systems. This conversion process is achieved through a so-called gateway. Depending on the vehicle, the gateway may be installed in the instrument cluster, in the vehicle power supply control unit, or in its own gateway control unit.