说明：  44B0的串口接收发送程序 **** 现在共享这样的代码有些过时了，但这是我参考很多例子才编写出来的。集合了很多优点：采用环形缓冲机制；读数据时不必关接收中断（没有几个人能实现的），所以不会存在数据丢失的可能；以数据帧为单位接收发送；能够缓冲几千个数据帧(由FrameLen定义)。注：本来是为Modbus协议而编写的，后来简化了校验和Modbus规范。
(44B0 receiving this procedure**** now sharing some of the outdated code, But this is only reference to many examples of the preparation. Set a lot of advantages : Ring buffer mechanism; Reading of data without interruption to receive clearance (Few people realize), so there is no loss of data possible; Data frames sent to the receiving unit; to the thousands of buffer data frame (from FrameLen definition). Note : Originally, it was to Modbus prepared, but later simplified calibration and Modbus norms.)