CAN , LIN communication

・In Japanese

■What is CAN communication?

CAN is an abbreviation for Controller Area Network, which is a serial communication standard mainly used as a communication network for automobiles, and is P2P (peer-to-peer) that communicates between Electronic Control Unit(ECU) without a host computer. The maximum communication speed is about 1 Mbps, and there are also higher speed (8 Mbps) communication such as CAN FD (CAN with Flexible Data rate).

＜merit＞
To input the sensor value to the ECU, it is necessary to connect the sensor and the ECU with a hard wire. When multiple ECUs require the same sensor value, if there is no CAN communication, the ECUs will be connected with as many hard wires as there are sensors, and the vehicle as a whole will require a lot of hard wires and input / output circuits. The cost will increase. When using CAN communication, it is possible to significantly reduce costs by using a common hard wire for communication between ECUs as shown below.



＜feature＞
The topology is bus type. The main ECUs are connected by the main bus, and each ECU is connected by the subbus from there. The main ECU is equipped with a terminating resistor to prevent signal reflection. However, this main ECU is not the master on the communication protocol, and it is a multi-master system with no superiority or inferiority between ECUs in terms of communication. In addition, half-duplex communication in which transmission and reception are performed alternately on one line, and differential signal transmission to improve noise immunity are used. The two CAN signal lines are not for transmission and reception, but for differential signal transmission. Sending and receiving is done by one line.

■What is LIN communication?

LIN is an abbreviation for Local Interconnect Network, and like CAN, it is a serial communication standard mainly used as a communication network for automobiles. The communication speed is slower than CAN communication, but the advantage is that it is cheaper. Cost reduction is possible by inputting multiple sensors to one ECU with a common hard wire. CAN is used for communication between ECUs, and LIN is used for communication between ECUs and sensors.



Other features are as follows.
・Single master method in which the unit becomes the master and commands the sensor to transmit.
・Half-duplex communication that alternates between sending and receiving on one line.
・Single-ended transmission that communicates on a single line.
・Communication speed is 20kbps, which is slower than CAN communication (1Mbps).

■Difference between CAN and LIN communication

The configuration example of CAN and LIN communication is as follows.



The comparison of communication methods is as follows.

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