最近在用STM32做一个脉冲计数的任务，很简单，就是在一定时间内计算出有多少个脉冲，我是通过tiM3进行输入捕获，然后把记到的数放到DMA里，然后用DMA产生中断，在中断里对10组数处理。用的是PB1口。
        但是程序并不是像我想的一样， 在用信号发生器去给一个固定的脉冲的时候，DMA里的10个数并不一样，而且随着脉冲频率的加快，DMA进入中断的速度也加快了，自己感觉代码没有问题，这里附上代码，希望各位前辈批评指正，晚辈感激不尽！
代码略长，希望各位前辈多指教！( 这里不可以上传代码，我就直接复制粘贴了)


#include "stm32f4xx.h"
#include "hardware_conf.h"
#define TIM3_CCR4_ADDRESS    0x40000440
#define TIM3_CNT_ADDRESS     0x40000424
u16 TIM3_Buffer[10]={0};  //用于缓存计数值
         
         
void TIM3_initial(void)//计数
{
  GPIO_InitTypeDef  GPIO_InitStructure;
  TIM_TimeBaseInitTypeDef TIM_BaseInitStructure;
  TIM_ICInitTypeDef  TIM_ICInitStructure;
  /* TIM1 clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
  /* GPIOB clock enable */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
  TIM_DeInit(TIM3);//初始化TIM3寄存器

  /* TIM3 channel 3 pin (PE.11) configuration */
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_1;
  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_NOPULL;
  GPIO_Init(GPIOB, &GPIO_InitStructure);
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource1, GPIO_AF_TIM3);

  TIM_BaseInitStructure.TIM_Period = 65535;              //周期
  TIM_BaseInitStructure.TIM_Prescaler = 10;          //预分频
  TIM_BaseInitStructure.TIM_ClockDivision = 1;
  TIM_BaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM3, &TIM_BaseInitStructure);

  TIM_ICInitStructure.TIM_Channel = TIM_Channel_4;
  TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;
  TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  TIM_ICInitStructure.TIM_ICFilter = 0x0;
  TIM_ICInit(TIM3, &TIM_ICInitStructure);
  DMA_Cmd(DMA1_Stream2, ENABLE);
  TIM_DMACmd(TIM3, TIM_DMA_CC4, ENABLE);
  /* TIM enable counter */
  TIM_Cmd(TIM3, ENABLE);
}

void TIM3_DMA_Config(void)         //计数的DMA函数
{
  NVIC_InitTypeDef NVIC_InitStructure;
  DMA_InitTypeDef DMA_InitStructure;


  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1 , ENABLE);
  DMA_InitStructure.DMA_Channel = DMA_Channel_5;         
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)TIM3_CCR4_ADDRESS ;                        
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)TIM3_Buffer;          //存放计数数组
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
  DMA_InitStructure.DMA_BufferSize = 10;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Enable;
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(DMA1_Stream2, &DMA_InitStructure);
  DMA_Cmd(DMA1_Stream2, ENABLE);
  DMA_ITConfig(DMA1_Stream2, DMA_IT_TC, ENABLE);//使能DMA中断，在接收完10个数据之后产生中断

  NVIC_InitStructure.NVIC_IRQChannel = DMA1_Stream2_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
  DMA_Cmd(DMA1_Stream2, ENABLE); //使能DMA1_Steam2
}
//这里是DMA中断里的处理，我这里有个LCD屏，我是在屏上去观察计数的值。

#include "stm32f4xx_it.h"
#include "hardware_conf.h"
#include "DMA_CESU.H"
#include "CeSu_INIT.H"
#include "ili932x_conf.h"

extern u16 Dispaly_Buffer[10];
extern u16 TIM3_Buffer[10];
int c=0;
#define           LED0          PAout(0)
void DMA1_Stream2_IRQHandler(void)         //DMA接受完成中断
{
  u8 i=0,a=0;
  LED0=~LED0;
  /* Test on DMA Stream Transfer Complete interrupt */
  if(DMA_GetITStatus(DMA1_Stream2, DMA_IT_TCIF2))
  {
          for(i=0;i