Systick 更新

之前写的systick_config(loadvalue) 根据系统时钟为72Mhz来写的，如果system clock不是72MHz怎么办？

重新写了一下，先获取，系统时钟频率。

 //参数为ms
 void Systick_Init(u16 ms)
 {
     RCC_ClocksTypeDef RCC_Clocks;
      /* SystTick configuration: an interrupt every 1ms */
     RCC_GetClocksFreq(&RCC_Clocks);
     SysTick_Config(ms*RCC_Clocks.SYSCLK_Frequency / );
     NVIC_SetPriority (SysTick_IRQn, );
 }

Systick_Init

说下关键的RCC_ClocksTypeDef

 typedef struct
 {
   uint32_t SYSCLK_Frequency;  /*!< returns SYSCLK clock frequency expressed in Hz */
   uint32_t HCLK_Frequency;    /*!< returns HCLK clock frequency expressed in Hz */
   uint32_t PCLK1_Frequency;   /*!< returns PCLK1 clock frequency expressed in Hz */
   uint32_t PCLK2_Frequency;   /*!< returns PCLK2 clock frequency expressed in Hz */
   uint32_t ADCCLK_Frequency;  /*!< returns ADCCLK clock frequency expressed in Hz */
 }RCC_ClocksTypeDef;

RCC_ClocksTypeDef