关于输入捕获测速问题

夜愿晨城 · 发表于 2016-10-17 16:30:50

因为我的速度比较低，按频率说的话大概不到3k，所以用输入捕获来测速
[mw_shl_code=c,true]
void TIM5_CH1_Cap_Init(u32 arr,u16 psc)//psc=84-1;arr=0XFFFFFFFF
{
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 = 6;
  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=3;
NVIC_InitStructure.NVIC_IRQChannelSubPriority =0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);

}

void TIM5_IRQHandler(void)
{
if(TIM_GetITStatus(TIM5, TIM_IT_CC1) != RESET)
{
   last_cnt=now_cnt;
   now_cnt=TIM_GetCapture1(TIM5);;
   if(now_cnt>=last_cnt)
   {
   w_main=now_cnt-last_cnt;
   }
else
{
   w_main=0xFFFFFFFF-last_cnt+now_cnt;
}

}

TIM_ClearITPendingBit(TIM5, TIM_IT_CC1|TIM_IT_Update);
}[/mw_shl_code]

程序大概就是上面这个样子，测试用频率为2khz，所以应该输出500，我在主程序输出w_main的时候，如下：（我是每隔1ms输出一次）
w_main  498.000000
w_main  2.000000
w_main  4.000000
w_main  500.000000
w_main  12.000000
w_main  25.000000
w_main  500.000000
w_main  498.000000
w_main  500.000000
w_main  25.000000
w_main  500.000000
w_main  1447.000000
w_main  480.000000
w_main  500.000000
w_main  500.000000
w_main  496.000000
w_main  491.000000
w_main  370.000000
w_main  15.000000
w_main  493.000000
w_main  500.000000
w_main  496.000000
w_main  500.000000
w_main  454.000000
w_main  7.000000
w_main  44.000000

简直惨不忍睹，第二个就是，我是用另一个板子做的波输入，在我还没有上电的时候就会有一堆输出，拔掉杜邦线就会消失，感觉像是干扰，但是不明白来自哪里，上电之后就像上面那样。跑来求助，希望知道的帮我看一下，谢谢！