What is serial communication? A communication method that uses one or two transmission lines to send and receive data, one bit at a time. Since it can be connected with fewer signal lines, it has the advantage of suppressing the cost of wires and transfer devices. RS-232, RS-422 and RS-485 are three common serial communication standards, each with different characteristics and application scenarios. The following is a detailed comparison of these three standards:   RS-232 RS232 is a 9-pin (DB-9) or 25-pin (DB-25) serial communication port on older computers. Features Communication mode: Single-ended Transmission distance: Usually within 15 meters (50 feet), depending on the baud rate and cable quality Baud rate: From 300 bps to 115200 bps, or even higher Voltage: The signal voltage is usually between ±3V and ±25V, and the voltage range of logic 0 and logic 1 is wide Signal line: mainly transmit data (TXD), receive data (RXD), ground (GND), etc. Application Usually used for short-distance communication between computers and peripheral devices (such as modems, printers) Advantages Simple and easy to implement Widely compatible, supported by many devices Disadvantages Limited communication distance Simplex communication, unable to perform two-way data transmission at the same time (although half-duplex can be achieved through control lines) RS-422 RS-232C has the disadvantages of short transmission distance and slow transmission speed. RS-422A is a specification formed by improving these disadvantages. It is also called “EIA-422A”. Although the purpose and timing of each signal line are specified, the connector is not specified. Many products that support EIA-422A mainly use D-SUB 25-pin or D-SUB 9-pin. Features Communication mode: Differential Transmission distance: usually up to 1200 meters (4000 feet) Baud rate: from 300 bps to 10 Mbps Voltage: The signal is transmitted via differential voltage, usually ±2V to ±6V Signal: usually includes data transmission (TX+, TX-), data reception (RX+, RX-) Application Suitable for long distance and high data transmission rate occasions, such as industrial control systems and data acquisition systems Advantages Support longer transmission distance Higher anti-interference ability due to the use of differential signals Support half-duplex and full-duplex communication Disadvantages More complex to implement than RS-232 Requires differential receiver and transmitter RS-485 This is a specification that was formed to improve the shortcoming of RS-422A, which has a small number of connections. It is also called “EIA-485”. RS-485 is a specification that is upwardly compatible with RS-422A. Although the purpose and timing of each signal line are specified, the connector is not specified. Many products that support EIA-422A mainly use D-SUB 25-pin or D-SUB 9-pin. Features Communication mode: Differential Transmission distance: typically up to 1200 meters (4000 feet) Baud rate: from 300 bps to 10 Mbps Voltage: Signals are transmitted via differential voltage, typically ±1.5V to ±5V Signal lines: mainly data lines (A, B) and ground lines (GND), supporting multi-point bus structure Application Widely used in industrial automation, building management and multi-point communication systems Advantages Supports multi-point communication, up to 32 devices can be connected (more devices are also possible through appropriate drivers and receivers) High anti-interference ability due to the use of differential signals Capability of long distance and high data transmission rate Disadvantages More complex to implement than RS-232 Requires correct terminal matching and network design Summary and comparison RS-232: Suitable for short-distance, simple point-to-point communication, easy to implement, but not suitable for long-distance and multi-point communication. RS-422: Supports long-distance communication and higher speed, but is mainly used for point-to-point or multi-point (up to 10 devices) communication. RS-485: Most suitable for long-distance, multi-point (up to 32 devices) communication, with high anti-interference and flexible network topology, but the implementation complexity is high. The maximum communication distance of RS232 port is 15 meters, while the maximum communication distance of RS422/485 is 1200 meters. To obtain purchase information and related information, please contact us: emi-ic.com