How to test the quality of the serial port cable of DB Connector?

How to test the quality of the serial port cable?

1. Use a multimeter to test whether the two ends are connected directly with a multimeter to determine whether the two ends are connected, just test 2/3/5 pins. To measure the female head, you need to put the multimeter into the pin air. Because the measuring end of the multimeter is relatively thick, it is necessary to weld two relatively thin metal pins or pins with resistance to the pins of the multimeter to facilitate the measurement of the female head. Use the multimeter to measure 2/3/5 of the serial cable. When measuring, use a straight connection, 2/3/5 corresponds to 2/3/5, and cross-wire 2 to 3, 3 to 2, 5 to 5 for measurement (that is, the 2 on one end of the cross serial port is measured at the other end of 3).

2. The situation of using the serial port assistant to send and receive is to connect RXD to TXD and TXD to RXD, use the serial port assistant to short-circuit the 2/3 pin of DB9, and use the serial port assistant to send data. If there is no problem with the serial port, self-transmit and self-receive can be realized.