CAN bus communication system

Abstract

The embodiment of the invention discloses a CAN bus communication system. The CAN bus communication system comprises a constant current source and a group of differential transmission lines, wherein the differential transmission lines comprise a CANH line and a CANL line. The positive electrode end of the constant current source is electrically connected with the CANL line, and the negative electrode end of the constant current source is electrically connected with the CANH line. According to the embodiment of the invention, the external constant current source can provide a reverse current for the CAN bus, which is equivalent to reducing the output resistance of the bus when the hidden level is transmitted, so that the time for the bus to jump to the hidden level when the bus has relatively large parasitic capacitance can be obviously reduced, and further the error rate is reduced and the transmission accuracy is improved. Meanwhile, the CAN bus communication system is provided with a terminal resistor, the positive electrode end of the constant current source is electrically connected with the CANL line, and the negative electrode end of the constant current source is electrically connected with the CANH line, so that the steady-state voltage of the CAN bus communication system is reduced to a negative value, the difference between a hidden level threshold value and the steady-state voltage is increased, the error rate is further reduced, and the accuracy of bus signal transmission is improved.

Description

technical field [0001] The embodiment of the present invention relates to the technical field of communication, in particular to a CAN bus communication system. Background technique [0002] The CAN bus is widely used in the fields of automobiles and automation. The physical layer and link layer protocol of the OSI model are clearly defined in ISO11898. [0003] A standard CAN bus communication system usually consists of multiple stations integrating transceivers, a pair of differential transmission lines (two wires, usually named CANH lines, CANL lines), and two 120-ohm terminal resistors. [0004] Compared with other bus systems based on differential transmission (such as RS422, RS485), CAN bus is outstanding in that it defines "dominant level" and "recessive level"; when any station sends "dominant level" ", the transmission content of the entire bus communication system is "dominant level", when all stations are in the receiving state or sending "recessive level", the t...

AI Technical Summary

Problems solved by technology

[0006] During the transition from the dominant level to the recessive level of the CAN bus communication system, as the communication distance increases, the parasitic capacitance and inductance increase, causing the system to jump from the dominant level to the recessive level. Time increases, the bit error rate increases, and the transmission uncertainty increases

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