How to fix the connection error of serial debug cable and RS232?

Serial debug line and RS232 connection errors are common in the following cases:

1. The line sequence is not correct: the serial debug line and RS232 need to match each other. RS232 pin numbers 1-9 are CD (carrier detection), RX (data reception), TX (data transmission), DTR, GND (ground), DSR (data device ready), RTS (request to send), CTS (clear to send) and RI (ringing indication), in that order. The serial debug line, on the other hand, usually has only three wires (RX, TX and GND) and needs to be interconnected with RX, TX and GND in the RS232 pins. If the connection is wrong, it will lead to data transmission failure.

2. Port parameter setting error: When using the serial debug line to communicate with RS232, you need to set the port parameters, such as baud rate, data bits, stop bits, etc.. If set incorrectly, it will also lead to data transmission failure.

3. Hardware failure: If the connection is correct and the port parameters are set correctly, but the communication still fails, it is possible that the serial debugging cable or RS232 itself is faulty.

The methods to repair the above problems are as follows:

1. The line sequence is not correct: usually you can check the pin number to determine whether the line is correct, or use a multimeter to measure the resistance value of each line. If the line sequence is not correct, you need to reconnect the line to ensure that the RS232 pins match each other.

2. The port parameters are set incorrectly: when setting the port parameters, you need to ensure that they match the RS232 configuration, which can usually be found in the device manager of the operating system for serial port settings. If you are not sure of the specific settings of the parameters, you can check the manual of RS232, or check the relevant information.

3. Hardware failure: If the connection and port parameters are correct, but the communication still fails, you need to check whether there is a hardware failure. You can try to replace another computer or replace the serial debugging cable, RS232 and other hardware devices to see if the problem can be repaired. If not, you need to send the device back to the manufacturer for repair.