The RS232 serial port line is used for serial communication between devices and has a wide range of applications. The serial port line has high compatibility, and is the most common application: desktop computers are connected to various serial port devices, such as computers and tax control machines, digital machine tools, PDA, Modem, set-top boxes, barcode machines, industrial instruments and other serial port devices for communication functions!
The connection method of RS232 serial port depends on the actual connected device. Let's look at the pin definition first. At present, the RS232 serial cable interface is DB9 pin, and its interface pins are defined as follows:
As shown in the figure above, the pins of the RS232 serial port interface are divided into upper and lower rows. How to distinguish the pins of the serial port line?
In the case of facing the human face and the large side of the interface facing up: a row of 5 pins, from left to right, corresponding to pins 1-5; a row of 4 pins, from left to right, corresponding to pins 6-9 .
pin definition symbol
1 Carrier detect DCD
2 Receive data RXD
3 send data TXD
4 The data terminal is ready for DTR
5 signal ground SG
6 Data ready for DSR
7 Request to send RTS
8 Clear to send CTS
9 Ringing reminder RI
The definition of the core color of the RS232 serial port line of Greenlink:
When users need to DIY Greenlink RS232 serial cable, they can wire according to the color of the core.
According to different needs, RS232 serial port connection methods are divided into two types: direct connection and crossover.
The RS232 serial cable direct connection method is the normal connection: 2 to 2, 3 to 3 (that is, the RX of one end is connected to the RX of the other end, and the TX is connected to the TX of the other end),**绿联 RS232串口线为直连接法；**
The RS232 serial cable cross connection method is cross connection: 2 to 3, 3 to 2 (that is, the RX at one end is connected to the TX at the other end, and the TX is connected to the RX at the other end).
Then what occasions are the direct connection and crossover connection of the RS232 serial port line used?
Under normal circumstances, the connection and communication between the device and the computer requires a direct connection of the RS232 serial port line;
The connection and communication between equipment and equipment will use the crossover line of RS232 serial port line. When choosing, users should choose RS232 serial cables with different connection methods according to the actual situation of the connection between the two devices.