stm32延时函数初始化，微秒，纳秒的初始化函数-the stm32 delay function initialization, microsecond, nanosecond initialization function

STM32的一个点亮流水灯的演示程序，两只LED交替点亮，内含时间的精确延迟-The STM32 a light water lights demo program, the two LEDs alternately light, containing the time delay accurate