RS-485 multipoint communication method

Abstract

The RS-485 multipoint communication method includes balanced sending and differential receiving for the communication between one master machine and several slave machines. In the sending end, upper layer data is first received, protocol head is added before the data byte and CRC check is added behind the data byte, before initializing treatment and sending the data frame. In the receiving end, after the data frame is received, the frame decomposing treatment including frame head distinction, dingle board address comparison, frame length checking, data byte determination and CRC is performed before the corresponding treatment of received pure load. The present invention raises communication efficiency, facilitates RS-485 debugging, locates error correctly and increases the measurement performance while ensuring the reliability of multipoint communication.

Description

technical field [0001] The invention relates to a method for realizing serial communication standards, in particular to a method for realizing RS-485 multipoint communication. Background technique [0002] In data communication, computer network and industrial distributed control system, it is often necessary to use serial communication to achieve the purpose of remote information exchange. Because the serial communication method has fewer lines and low cost, especially in long-distance transmission, It avoids the inconsistency of the characteristics of multiple lines and is widely used. In serial communication, both communication parties are required to adopt a standard interface, so that different devices can be easily connected for communication. Interface standards currently available for serial communication include RS-232, RS-422, RS-423 and RS-485. RS232 is the earliest serial interface standard, and it has been widely used in short-distance, lower baud rate serial ...

AI Technical Summary

Problems solved by technology

[0005] The 485 bus supports communication between multiple devices. Generally speaking, the communication protocols between multiple devices are relatively complicated. However, the data volume of each interaction between multiple devices using 485 communication is relatively small. The communication protocol will greatly reduce the communication efficiency and take up a lot of CPU resources, but the use of a relatively simple communication protocol will greatly reduce the reliability

And in the current 485 multipoint communication system, the address identification is mostly expressed by one byte or even several bits, which is easy to conflict with the data

For framing processing, the current system uses single-board address + data + checksum, and uses parity check and data checksum. The degree of error detection has great defects, and it is not testable.

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