The difference in application between RS485 and RS232: communication selection in industrial Internet of Things

In the vast world of Industrial Internet of Things (IIoT), the selection of communication protocols is the foundation for building stable and efficient systems. RS485 and RS232, as two classic serial communication standards, play important roles in different fields. However, for many practitioners in traditional industries, the application differences between these two protocols may not be very clear. This article will delve into the application differences between RS485 and RS232 from a professional perspective, providing a unique and in-depth insight for friends in traditional industries.

1、 Electrical characteristics and anti-interference ability

RS232

RS232, also known as Recommended Standard 232, is a serial communication standard that uses single-ended signal transmission. It uses a pair of transmission lines TX and RX for bidirectional communication, with signal levels transmitted directly through a single signal line. RS The signal level of 232 is relatively high, usually ranging from ± 3 to ± 25V, which makes it susceptible to external noise and interference during transmission. Therefore, RS 232 has relatively weak anti-interference ability and is suitable for communication in short distance and low-noise environments.

RS485

In contrast, RS485 adopts differential signal transmission method, which uses two signal lines A and B to transmit a pair of differential signals. This transmission method can effectively resist line interference and noise, and improve the stability and reliability of communication. RS The interface level of 485 is low, and logic "1" is represented by a voltage difference of+(2~6) V between two lines, while logic "0" is represented by a voltage difference of -2 to -6V between two lines. This design enables RS485 to perform well in harsh environments and long-distance transmission, with much stronger anti-interference capabilities than RS232.

2、 Transmission distance and speed

RS232

The transmission distance of RS232 is relatively short, usually not exceeding tens of meters, and the maximum transmission rate is generally 115.2 kbps. This limitation makes RS232 inadequate in applications that require long-distance or high-speed data transmission. However, due to its simplicity and ease of use, RS 232 still has a certain market in short-range communication.

RS485

RS485 supports long-distance communication, with a maximum communication distance of several kilometers depending on the transmission medium and signal quality. Meanwhile, RS The transmission rate of 485 is also much higher than RS232, up to 10 Mbps depending on the specific standard and device. This high-speed and long-distance transmission capability makes RS485 have significant advantages in fields such as industrial automation and building monitoring that require large-scale data transmission.

3、 Network topology and device interconnection

RS232

RS232 usually adopts point-to-point connection, that is, one-to-one communication connection. Although this topology structure is simple, it limits the interconnection capability between devices. In scenarios where multiple devices need to be interconnected, RS 232 may require additional relay devices or conversion modules to be implemented.

RS485

RS485 supports multi-point communication and can connect multiple nodes using a bus topology structure. This topology structure makes RS485 widely used in scenarios that require multi device interconnection, such as industrial automation and remote monitoring. RS The 485 bus generally supports a maximum of 32 nodes. If a specially designed 485 chip is used, more nodes can be reached to meet the needs of complex networks.

4、 Application Fields and Scenarios

RS232

Due to its simplicity and ease of use, RS 232 has been widely used in fields such as computer communication, industrial automation, and electronic equipment. It is usually used to connect computers with external devices such as modems, printers, scanners, etc., to achieve data transmission and control. In addition, RS 232 is also commonly used for data exchange and control between industrial equipment, such as PLC programmable logic controllers, sensors, instruments, etc.

RS485

RS485 plays an important role in industrial automation, building automation, safety monitoring, intelligent transportation, and other fields due to its long-distance transmission, high reliability, and multi-point communication capabilities. In the field of industrial automation, RS The 485 interface is widely used to connect various sensors, actuators, PLCs, and other devices to achieve data acquisition, monitoring, and control. In building automation systems, RS The 485 bus connects various subsystems such as lighting control, air conditioning control, security systems, etc., to achieve centralized management and control. In addition, RS 485 is also widely used for data acquisition and communication in the field of instrumentation.

There are significant differences between RS485 and RS232 in terms of electrical characteristics, transmission distance and speed, network topology and device interconnection, as well as application fields and scenarios. When choosing a communication protocol, it is necessary to consider comprehensively based on specific application requirements and scenarios. For situations that require long-distance, high-speed, and multi device interconnection, RS 485 is undoubtedly a better choice; For short distance and simple connection scenarios, RS 232 has the advantages of low cost and easy implementation. With the continuous development of industrial Internet of Things, choosing the appropriate communication protocol will be crucial for building stable and efficient systems.