串口状态的检测,可以检测到连接串口的设备是否正常连接或是哪种设备-state tests can detect serial port to connect the equipment or normal connecting what equipment

实现用串口收发数据，开启串口，采用轮询的方式不断检测是否有串口的数据的到来-Implementation used to send and receive serial data, open the serial port, using polling manner Detect Whether or not there is the advent of serial data