说明：  目前较为常用的串口有9针串口（DB9）和25针串口（DB25），通信距离较近时(<12m)，可以用电缆线直接连接标准RS232端口(RS422,RS485较远)，若距离较远，需附加调制解调器（MODEM）。最为简单且常用的是三线制接法，即地、接收数据和发送数据三脚相连，本文只涉及到最为基本的接法，且直接用RS232相连
(At present, the more commonly used 9-pin serial port serial port (DB9) and 25-pin serial port (DB25), when the communication distance of more recent (<12m), can be directly connected to standard power cable RS232 port (RS422, RS485 away), If the distance required to attach a modem (MODEM). The most simple and commonly used is a three-wire connection, that is, the receive data and send data three-connected, this article only relates to the most basic access method, and directly connected to RS232)