STM32的通用I/O介绍小程序，是STM32的入门学习程序。-STM32 Universal I/O introduced applet is STM32 entry-learning process.

STM32的USART操作，从零开如讲解，细仔深入，希望能帮到初学者-STM32 USART operation from scratch, such as explaining, careful in-depth, and I hope to help beginners