说明：  arm实验时编写的linux串口程序，实现了基本的串口通讯功能，并在接收报文时，使用了环形缓冲区，希望程序对大家有所帮助，如有Bug，请给我留言，谢谢。
(arm experiments prepared by the linux serial procedures to achieve the basic serial communications functions, the reported receiving text, the use of the circular buffer, we have procedures to help, if Bug. please give me a voice, thank you.)