In the fields of industrial automation, communications, and data transmission in various electronic devices, serial communication standards are crucial. The RS232 bus standard and the RS485 bus standard are two common and widely used serial communication standards. This article will explain in detail the significant differences in performance and application scenarios between the RS232 and RS485 bus standards.
RS232 standard
RS232 interface wiring diagram
The RS232 interface is one of the earliest serial communication standards and was developed by the Electronic Industries Association (EIA).
1. RS232 interface and line
The RS232 interface usually uses the DB9 interface to realize data transmission through three wires (sending wire, receiving wire and ground wire).
2. RS232 standard level logic
The RS232 standard uses negative logic. The level range of logic "1" is -5V to -15V, and the level range of logic "0" is +5V to +15V.
3. RS232 performance characteristics
The RS232 standard has relatively weak anti-interference ability and is susceptible to external electromagnetic interference. The transmission distance is generally about 15 meters. - It is a full-duplex communication mode that can send and receive data at the same time, but the transmission rate is usually within 20Kbps.
4. RS232 standard application scenarios
The RS232 standard is suitable for short-distance, direct connections between devices, such as connections between computers and modems, mice, printers and other devices.
RS485 standard
What is RS485 interface
RS485 bus standard Compared with the RS232 standard, the RS485 interface has many significant advantages.
1. RS485 transmission distance
The RS485 bus transmission distance can reach more than 1,200 meters, far exceeding the 15-meter limit of the RS232 standard transmission distance. It is suitable for long-distance communication IoT application scenarios such as large industrial sites and remote monitoring systems.
2. RS485 signal transmission
The RS485 bus standard adopts a two-wire differential signal transmission method. Logic "1" is represented by the voltage difference between the two lines as +(2 - 6)V, and logic "0" is represented by the voltage difference between the two lines as -(2 - 6) V means that it has strong anti-interference ability and can maintain stable data transmission in harsh electromagnetic environments.
3. RS485 communication mode
The RS485 protocol is a half-duplex communication. It can only send or receive data at the same time, but multiple transceivers can be connected to the bus. It supports 1-to-many communication and can theoretically connect up to 32 nodes. When building a multi-device communication network More flexibility and cost-effectiveness.
4. RS485 transmission rate
The standard transmission rate of the RS485 bus can reach 10Mbps, which is much higher than the RS232 standard and meets the needs of high-speed data transmission.
RS485 does not have a standard interface form and usually uses industrial wiring terminals to facilitate installation and maintenance in industrial environments.
Selection and application scenarios of RS232 and RS485 standards
In actual applications, whether to choose the RS232 bus or the RS485 bus depends on the specific needs of the application solution. For example, if the solution is short-distance, point-to-point communication, with low transmission rate requirements and a small number of devices, it is recommended to give priority to RS232; if the application scenario requires long-distance communication, connection of multiple devices, and industrial control and automation systems with high anti-interference capabilities, Then the RS485 bus is often a better choice.
Differences between RS232 and RS485
| Features | RS232 | RS485 |
| Voltage level | ±15V (±12V typical) | Differential signal transmission, generally ±5V to ±6V |
| Signal type | Single-ended signal | Differential signal |
| Communication distance | Short, up to 15 meters (50 feet) | Long, up to 1200 meters (4000 feet) or more |
| Environmental adaptability | Vulnerable to electromagnetic interference | Good anti-interference performance |
| Application | PC peripheral connections, short-distance data transmission | Industrial automation, multi-point communication network |
| Interface complexity | Relatively simple | More complex, need to consider differential signal and terminal resistance |
| Data rate | Usually low | Support high-speed data transmission |
| Line configuration | Simple or half-duplex | Full-duplex |
To sum up, although the RS232 bus and the RS485 bus are both serial communication standards, they have differences in transmission distance, communication mode, anti-interference ability, transmission rate and the number of connectable nodes. These differences and characteristics are also applicable to each. in different IoT application scenarios. Understanding these differences is critical for proper selection and application for efficient, stable data transmission.
