输入捕获测量频率时,测量的频率变大后就一直测量为零

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再用输入捕获实验测量信号的频率时,低频时能正常测量到,但是稍微高一点就一直测量值为0,TIM_GetCapture1()里面也是0,主要是这个高频还不到1KHz,就测不到了,用的定时器14输出PWM波,用定时器TIM5对PWM信号进行捕获,希望各位朋友帮我看下怎么回事.下面是代码
定时器TIM14,产生PWM波,

void TIM14_PWM_Init(u32 arr,u32 psc)
{                              
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    TIM_OCInitTypeDef  TIM_OCInitStructure;
   
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM14,ENABLE);   
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOF, ENABLE);   
   
    GPIO_PinAFConfig(GPIOF,GPIO_PinSource9,GPIO_AF_TIM14);
   
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;         
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;      
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;   
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;   
    GPIO_Init(GPIOF,&GPIO_InitStructure);            
      
    TIM_TimeBaseStructure.TIM_Prescaler=psc;
    TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;
    TIM_TimeBaseStructure.TIM_Period=arr;   
    TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1;
   
    TIM_TimeBaseInit(TIM14,&TIM_TimeBaseStructure);
   
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
    TIM_OC1Init(TIM14, &TIM_OCInitStructure);

    TIM_OC1PreloadConfig(TIM14, TIM_OCPreload_Enable);

  TIM_ARRPreloadConfig(TIM14,ENABLE);//ARPEʹÄÜ
   
    TIM_Cmd(TIM14, ENABLE);   //ʹÄÜTIM14        

}  


定时器TIM5,对pwm信号进行输入捕获
TIM_ICInitTypeDef  TIM5_ICInitStructure;

void TIM5_CH1_Cap_Init(u32 arr,u16 psc)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5,ENABLE);      
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);     
   
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
    GPIO_Init(GPIOA,&GPIO_InitStructure);

    GPIO_PinAFConfig(GPIOA,GPIO_PinSource0,GPIO_AF_TIM5);
  
      
    TIM_TimeBaseStructure.TIM_Prescaler=psc;  
    TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;
    TIM_TimeBaseStructure.TIM_Period=arr;  
    TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1;
   
    TIM_TimeBaseInit(TIM5,&TIM_TimeBaseStructure);
   
    TIM5_ICInitStructure.TIM_Channel = TIM_Channel_1;
  TIM5_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
  TIM5_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM5_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;   
  TIM5_ICInitStructure.TIM_ICFilter = 0x00;
  TIM_ICInit(TIM5, &TIM5_ICInitStructure);
        
    TIM_ITConfig(TIM5,TIM_IT_Update|TIM_IT_CC1,ENABLE);
   
  TIM_Cmd(TIM5,ENABLE );
  NVIC_InitStructure.NVIC_IRQChannel = TIM5_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority =0;  
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;           
    NVIC_Init(&NVIC_InitStructure);   
}
输入捕获中断程序
void TIM5_IRQHandler(void)
{         
      CaptureValue1 = TIM_GetCapture1(TIM5);
      CaptureValue2 = TIM_GetCounter(TIM5);   
  if (CaptureValue1 != 0)
  {
         CaptureFrequency=CaptureValue1;
         CaptureFrequency =1000000 / CaptureValue1;   
         TIM_SetCounter(TIM5,0);
  }
  else {CaptureFrequency = 999; }
  TIM_ClearITPendingBit(TIM5, TIM_IT_CC4|TIM_IT_Update);
}


在主函数中打印频率和 TIM_GetCapture1(TIM5)、TIM_GetCounter(TIM5); 的值，printf("%d  %d   %d  \r \n",CaptureFrequency,CaptureValue1,CaptureValue2);初始化时TIM14_PWM_Init(5000-1,84-1);   TIM5_CH1_Cap_Init(0XFFFFFFFF,84-1); TIM14_PWM_Init（）中的arr减小到2000以下,测量值就为0了. 本人刚接触STM32不久,希望大家帮帮忙,谢谢大家了