RS-232 is a serial data interface standard, which was originally formulated and published by Electronic Industry Association (EIA). RS-232 was published in 1962 and named EIA-232-E as an industrial standard to ensure the compatibility of products from different manufacturers.

RS-232 is one of the communication interfaces on personal computers, and it is an asynchronous transmission standard interface formulated by Electronic Industry Association (EIA).

Usually, the RS-232 interface appears in the form of 9-pin (DB-9) or 25-pin (DB-25). There are two sets of RS-232 interfaces on a personal computer, which are called COM 1 and COM2 respectively.

Extended data:

Disadvantages of RS232 interface:

Due to the early appearance of RS-232-C interface standard, there are inevitable shortcomings, mainly including the following four points:

(1), the signal level of the interface is high, which is easy to damage the chip of the interface circuit, and because it is not compatible with TTL level, it is necessary to use a level shift circuit to connect TTL circuit.

(2) Low transmission rate. In asynchronous transmission, the baud rate is 20Kbps.

(3) The interface adopts signal lines and signal loops, forming a * * * ground transmission form, which is easy to generate * * * mode interference and has weak anti-noise interference.

(4) The transmission distance is limited. The standard value of the maximum transmission distance is 50 feet, but it can only be used at about 50 meters.

Reference source: Baidu Encyclopedia -RS-232 protocol.