Serial communication is mainly divided into three communication methods: RS232, RS422, and RS485. RS232RS-232 is a serial connection standard on IBM-PC and its compatibles. Full-duplex communication requires three wires: a ground wire, sending a wire, and receiving wire.RS232/RS485 serial port communicationRS-232 is only limited to point-to-point communication between the PC serial port and the device, the anti-interference ability is poor, and the longest communication distance is 50 feet. RS-232 can be used for many purposes, such as connecting mice, printers, industrial instruments, and meters, and also for improving drive and connection. In practical applications, the transmission length or speed of RS-232 often exceeds the standard value. RS422RS-422 (EIA RS-422-A Standard) is a serial connection standard for Apple's Macintosh computers. It adopts a full-duplex communication mode, there are 4 signal wires, the receiving and sending are separated, and the receiving and sending can be carried out at the same time. The maximum transmission distance of the RS-422 interface is 4000 feet (about 1219 meters), and the maximum transmission rate is 10Mb/s.RS-422 uses differential signals as well as unbalanced ground-referenced signals. The differential transmission uses two wires to send and receive signals. Compared with RS-232, it can resist noise better and has a longer transmission distance. It is especially suitable in industrial environments.RS485RS-485 adopts a half-duplex communication mode. It increases the number of devices, and at the same time defines the electrical characteristics in the case of the maximum number of devices to ensure sufficient signal voltage. RS-485 has excellent noise immunity and multi-device capability, and RS-485 can be used for serial communication over 4000 feet of wire. RS485 adopts balanced transmission and differential reception, has good anti-interference ability, and the signal can be transmitted for thousands of meters. RS-422 devices can be controlled by RS-485.
