串口通信基本常识

初学串口通信，需了解0X8000以及0X4000是什么意思！

参考：
https://blog.csdn.net/CALL_LKC/article/details/74375126
https://www.cnblogs.com/think-in-java/p/5527389.html
https://blog.csdn.net/liangbin414/article/details/88422110

hal库串口参考相关知识：
https://www.cnblogs.com/UnfriendlyARM/p/10321838.html
https://blog.csdn.net/qq_33559992/article/details/76218291