stm32 点亮第一个led，利用库函数操作，通过位带映射，快速改变IO口的状态-stm32 lit the first one led, the use of library functions operate through bit-band mapping, rapidly changing IO port status

芯嵌stm32上电，按下按键K1或K2，会触发一个外部中断，对应的LED就会点亮。-Core embedded on stm32 power, press the button K1 or K2, will trigger an external interrupt, the corresponding LED will light up.

STM32串口调试程序，发送一个字符，或者是点亮一个LED。-Serial debugging procedures