(1) Serial communication refers to the serial port sending and receiving bytes in bits. Although slower than parallel communication by byte, the serial port can use one line to send data while receiving data on another line. In serial communication, commonly used protocols include RS-232, RS-422, and RS-485.
(2) The serial communication we usually say is the RS232 serial port of the default computer, and the RS485 interface is differential, which is used in areas with high reliability. If the computer's RS232 wants to communicate with RS485 equipment, it must use an RS232 to RS485 adapter.
(3) There are two commonly used serial port connectors, one is a 9-pin serial port (referred to as DB-9), and the other is a 25-pin serial port (referred to as DB-25). Each type of connector is divided into male and female. Among them, the connector with a needle is a male and the connector with a hole is a female.
(4) The most important parameters of serial communication are bit rate, data bits, stop bits, and parity. For two communication ports, these parameters must match.