RS485 communication circuit and fault detection method of nodes applying the circuit

Abstract

The invention discloses an RS485 communication circuit. The circuit comprises a microprocessor, a first isolating circuit, a second isolating circuit, a third isolating circuit, a first RS485 transceiver, a second RS485 transceiver, a switching circuit and a switching drive circuit; the microprocessor is respectively connected with one end of the first RS485 transceiver, one end of the second RS485 transceiver and the input end of the switching drive circuit through the first isolating circuit, the second isolating circuit and the third isolating circuit; the output end of the switching drive circuit is connected with the control input end of the switching circuit; and the first breakover end, the second breakover end and the third breakover end of the switching circuit are respectively connected with the other end of the first RS485 transceiver, the other end of the second RS485 transceiver and an RS485 bus. The invention also discloses a fault self-detection method of the RS485 communication circuit and a method for detecting the communication faults of a slave node and a main node applying the RS485 communication circuit. In adoption of the technical solution, the node on the RS485 communication circuit can detect whether there is a fault by itself.

Description

technical field [0001] The invention relates to RS485 bus communication technology. Background technique [0002] As a commonly used communication bus in the industrial field, RS485 communication is widely used for its long communication distance, stable communication and simple wiring. However, as a master-slave communication bus, in actual use, it is usually required that all nodes on the bus start with the master node, and the bus topology is adopted between the final nodes and connected in a "hand in hand" manner. [0003] For the existing equipment using RS485 bus communication, the schematic diagram of the internal RS485 communication circuit is as follows: figure 1 shown. The RS485 communication circuit includes a microprocessor chip 91 , a photoelectric isolation circuit 92 and an RS485 transceiver chip 93 . The TTL level serial communication on the microprocessor chip 91 and the RTS control pin are isolated by the photoelectric isolation circuit 92, connected to ...

AI Technical Summary

Problems solved by technology

[0004] The devices interconnected by the RS485 bus are installed in different locations in the industrial environment, and there may be strong electromagnetic interference around some devices or a certain segment of the bus. When the interference is severe, it will cause RS485 in the RS485 communication circuit of the device. The transceiver chip has a fault of a short-circuit nature

At this time, the entire network will be paralyzed and unable to communicate

The identification and removal of network failures usually requires manual on-site investigation, which is time-consuming and laborious, and it is easy to think that some faults have been caused during the investigation process.

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