1.systick时钟来源

2.SysTick库函数

#elif defined SYSCLK_FREQ_24MHz

  uint32_t SystemCoreClock         = SYSCLK_FREQ_24MHz;        /*!< System Clock Frequency (Core Clock) */

#elif defined SYSCLK_FREQ_36MHz

  uint32_t SystemCoreClock         = SYSCLK_FREQ_36MHz;        /*!

#elif defined SYSCLK_FREQ_48MHz

  uint32_t SystemCoreClock         = SYSCLK_FREQ_48MHz;        /*!

#elif defined SYSCLK_FREQ_56MHz

  uint32_t SystemCoreClock         = SYSCLK_FREQ_56MHz;        /*!

#elif defined SYSCLK_FREQ_72MHz

  uint32_t SystemCoreClock         = SYSCLK_FREQ_72MHz;        /*!

#else /*!< HSI Selected as System Clock source */

  uint32_t SystemCoreClock         = HSI_VALUE;        /*!< System Clock Frequency (Core Clock) */

#endif

 ///////////////////////////////

   /* Configure the SysTick */

SysTick_Config(SystemCoreClock / RT_TICK_PER_SECOND);//8000000/1000=>1ms

/**

 *This is the timer interrupt service routine.

 *

 */

void SysTick_Handler(void)

{

   /* enter interrupt */

   rt_interrupt_enter();

   rt_tick_increase();

   /* leave interrupt */

   rt_interrupt_leave();

}