Some computers have a 9-pin interface similar to VGA interface, that is, RS-232 communication interface, commonly known as "232 serial port", and the default port number on the computer is COM 1 or com2.

The function of RS-232 is similar to USB, and it belongs to bus interface. Different from USB, RS-232 interface has no power supply function, does not support hot plug, and its transmission speed is much lower than USB, so it is generally used to connect industrial equipment and instruments.

This kind of interface is rarely used by general computer peripheral products. Because the frequency of RS-232 interface in daily life is very low, many of the electricity used at present is cancelled by the brain. The following figure shows the RS-232 interface of the motherboard.

Extended data:

As an independent level conversion controller, the intelligent converter involves intelligent switching of online power supply, sending and receiving status, communication mode setting and conversion between RS-232 level and RS-485RS-422 level. The specific description is as follows:

Get power from RS-232 interface

Since external power supply mode is not adopted, power must be taken from RS-232 interface line to supply power to internal components. We know that in the standard RS-232 interface definition, TXD, RTS and DTR are RS-232 level outputs. Design a DC-DC converter, which can provide a certain power supply for the system from these signals.

Low power microprocessor

Microprocessor determines whether to allow data transmission and data reception by monitoring the change of TXD signal. In addition, the choice of communication mode, baud rate and half-duplex working mode is set through TXD signal or I/O port.

Conversion between RS-232 level and TTL level.

Conversion between RS-485RS-422 level and TTL level.

Baidu Encyclopedia -232 Interface