RS232 is a serial communication interface standard commonly used to connect computers and serial devices, such as modems, printers, etc. It is physically connected using DB9 or DB25 connectors. The following is the connection method of RS232:
< br >
For DB9 connectors:
Pin 1 (DCD) is connected to the receiving port of the modem or other device
Pin 2 (RD) is connected to the send port of the modem or other device
Pin 3 (TD) is connected to the send port of the computer
Pin 4 (DTR) is connected to the request sending port of the modem or other device
- Pin 5 (GND) is connected to the ground cable of the device
Pin 6 (DSR) is connected to the data terminal Ready state port of the device
Pin 7 (RTS) is connected to the request sending port of the computer
Pin 8 (CTS) is connected to the data terminal Ready port of the computer
< br >
For DB25 connectors:
Pin 2 (TD) is connected to the send port of the computer
Pin 3 (RD) is connected to the send port of the modem or other device
- Pin 4 (RTS) connects to the request sending port of the computer.
Pin 5 (CTS) is connected to the data terminal Ready port of the computer
Pin 6 (DSR) is connected to the data terminal Ready state port of the device
- Pin 7 (SG) is connected to the ground wire of the device
Pin 8 (CD) is connected to the receiving port of the modem or other device
Pin 20 (DTR) is connected to the request sending port of the modem or other device.
< br >
Note that different devices may have different connection requirements, please check the manual of the device you are connecting.
RS232 serial cable cross-connection method is cross-connection: 2 is connected to 3, 3 is connected to 2 (that is, RX at one end is connected to TX at the other end, TX is connected to RX at the other end) 5 is connected to 5. Note: Under normal circumstances, the connection of the device and the computer for communication, you need to use the RS232 serial cable directly connected; The connection of devices and devices for communication will use the cross line of RS232 serial port line.
Generally, RS232 can work only with these three wires: receiving RXD, sending TXD, and grounding GND. However, due to the difference in the shape of the interface, the pin number and the signal line category are different, and the common 9 pins and 25 pins are two kinds. Pin functions of the 25-pin serial port 2 Send data (TXD) 3 Receive data (RXD) 4 Send request (RTS) 5 Send Clear (CTS) 6 Data Ready (DSR) 7 Signal Ground (GND) 8 Carrier detection (DCD) 20 Data terminal ready (DTR) 22 Ringing indicator (RI) 9-pin serial port functions Overview Pin functions
1 Carrier Detection (DCD)
2 Receiving Data (RXD)
3 Send Data (TXD)
4 Data Terminal Ready (DTR)
5 Signal Ground (GND)
6 Data Readiness (DSR)
7 Send a Request (RTS)
8 Send Clear (CTS)