/* SystemFrequency / 1000    1ms中断一次

 * SystemFrequency / 100000     10us中断一次

 * SystemFrequency / 1000000 1us中断一次

 */

#define SYSTICKPERIOD                    0.000001

#define SYSTICKFREQUENCY            (1/SYSTICKPERIOD)

/**

  * @brief  定时器2的初始化,，定时周期1ms

  * @param  无

  * @retval 无

  */

void TIM2_Init(void)

{

    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

    /*AHB = 72MHz,RCC_CFGR的PPRE1 = 2，所以APB1 = 36MHz,TIM2CLK = APB1*2 = 72MHz */

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    /* Time base configuration */

    TIM_TimeBaseStructure.TIM_Period = ;

    TIM_TimeBaseStructure.TIM_Prescaler = SystemCoreClock/SYSTICKFREQUENCY -;

    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    TIM_ARRPreloadConfig(TIM2, ENABLE);

    /* 设置更新请求源只在计数器上溢或下溢时产生中断 */

    TIM_UpdateRequestConfig(TIM2,TIM_UpdateSource_Global);

    TIM_ClearFlag(TIM2, TIM_FLAG_Update);

}

/**

  * @brief   ms延时程序,1ms为一个单位

  * @param

  *        @arg nTime: Delay_ms( 10 ) 则实现的延时为 10 * 1ms = 10ms

  * @retval  无

  */

void Delay_ms(__IO uint32_t nTime)

{

    /* 清零计数器并使能滴答定时器 */

    TIM2->CNT   = ;

    TIM_Cmd(TIM2, ENABLE);     

    for( ; nTime >  ; nTime--)

    {

     /* 等待一个延时单位的结束 */

     while(TIM_GetFlagStatus(TIM2, TIM_FLAG_Update) != SET);

     TIM_ClearFlag(TIM2, TIM_FLAG_Update);

    }

    TIM_Cmd(TIM2, DISABLE);

}