串口访问功能的小测试程序

代码说明：

说明：  一个含串口访问功能的小测试程序，含多线程，CRC校验 此程序包含了一个串口通讯的类，并能够实现简单的通讯功能，希望对要用API函数写串口通讯程序的朋友有帮助 (a serial access function with a small test program, including multithreading, CRC procedure contains a serial communications category, and to achieve a simple communication, want to use API function to write the serial communication program to help friends)