1、 Introduction to can communication
1. Basic concept: CAN is the abbreviation of Controller Area Network (hereinafter referred to as CAN), and is the ISO world standardized serial communication protocol. In the automotive industry, various electronic control systems have been developed to meet the requirements of safety, comfort, convenience, low pollution, and low cost.
2. Physical characteristics of the CAN bus: The two signal lines of the CAN bus are called CANH and CANL, respectively. Assuming that the CANH level is greater than CANL, it is a Dominant (dominant level) that actually indicates signal 0; Assuming that the CANH level is equal to the CANL, it is Recessive, which actually indicates signal 1.
When the chip is powered by 5V and outputs 0, the output voltages of CANH and CANL are approximately 3.5V and 1.5V. When the output is 1, the two wires are floating to the ground with high resistance. The voltage is pulled to an equal value of approximately 2.5V through external termination resistors.