What does Serial port mean ?

The serial port is called the serial interface, and the PC generally has two serial ports COM 1 and COM 2

The difference between the serial port and the parallel port is that its data and control information are transmitted bit by bit.
 
Although the speed will be slower, the transmission distance is longer than that of the parallel port, so if you want to communicate over a longer distance, you should use the serial port.

Usually COM 1 uses a 9-pin D-shaped connector, also known as an RS-232 interface, while some COM 2 uses an old-fashioned DB25-pin connector, also known as an RS-422 interface, but there are very few use.

Serial port, or serial port, serial port, serial port, is mainly used for serial bit-by-bit metadata transmission. Common is the general computer RS-232 D-type 9-pin connector
 
RS-232 for applications (using a 25-pin or 9-pin connector), half-duplex RS-485 and full-duplex RS-422 for industrial computer applications.

The serial port is called the serial interface, also known as the serial communication interface, which includes RS-232-C, RS-422, RS485, USB, etc. according to electrical standards and protocols.

The RS-232-C, RS-422 and RS-485 standards only specify the electrical characteristics of the interface, and do not involve connecting plug-ins, cables or protocols.

USB is a new interface standard developed in recent years, mainly used in the field of high-speed data transmission

RS-232-C: Also known as standard serial port, it is the most commonly used serial communication interface.

It is a standard for serial communication jointly formulated by the Electronic Industries Association (EIA) of the United States in 1970 in conjunction with Bell Systems, modem manufacturers and computer terminal manufacturers.

Its full name is "Serial Binary Data Exchange Interface Technical Standard between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)".

The traditional RS-232-C interface standard has 22 wires and uses a standard 25-pin D-type plug socket. Later PCs used a simplified 9-pin D-type socket.

25-pin sockets are rarely used in today's applications. Today's computers generally have two serial ports: COM1 and COM2. You can see the 9-pin D-shaped interface behind the computer.

Nowadays, many mobile phone data lines or logistics receivers use COM ports to connect with computers.

RS-422: In order to improve the shortcoming of RS-232 communication distance and low speed, RS-422 defines a balanced communication interface, which increases the transmission rate to 10Mb/s and the transmission distance to 4000 feet (the rate is lower than 100kb/s). s) and allows up to 10 receivers on a balanced bus.

RS-422 is a one-way, balanced transmission specification for single-machine sending and multiple-machine receiving, and is named as the TIA/EIA-422-A standard.

In order to expand the scope of application of RS-485, EIA formulated the RS-485 standard on the basis of RS-422 in 1983, adding multi-point and two-way communication capabilities, that is, allowing multiple transmitters to be connected to the same bus. The driving ability and conflict protection characteristics of the transmitter are improved, and the common mode range of the bus is expanded, which is later named as the TIA/EIA-485-A standard.

USB to RS-422 Serial Cable

USB to RS-232 Serial Cable

USB to RS-485 Serial Cable