stm32定时器输入捕获的问题

你好我好大家好！提问时间：2015-7-1 18:12 /

现在用定时器做pwm捕获，计算pwm的频率，但是不知道为什么：引脚连接上固定频率的pwm信号后，捕获值为什么变化特别大：从0x00000080到0x0000D788，有么有大婶们遇到过这种情况啊,求指点？现贴代码如下：

   static void TIM_Config(void)
{
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
      TIM_OCInitTypeDef  TIM_OCInitStructure;
  TIM_ICInitTypeDef  TIM_ICInitStructure;
  GPIO_InitTypeDef GPIO_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;

  /* TIM1 ,TIM2 clock enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
  /* GPIOA clock enable*/
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
/*************************************** 配置TIM1产生固定频率的PWM*************************************/
/* TIM1 channel 1 pin  configuration */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* Connect TIM pins to AF2*/
      GPIO_PinAFConfig(GPIOA, GPIO_PinSource8, GPIO_AF_2);

  /* Time Base configuration */
  TIM_TimeBaseStructure.TIM_Prescaler = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = 0x9999;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
  TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

  /* Channel 1, 2,3 and 4 Configuration in PWM mode */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 1000;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
  TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
  TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;

  TIM_OC1Init(TIM1, &TIM_OCInitStructure);

  /* TIM enable counter */
  TIM_Cmd(TIM1, ENABLE);
  /* TIM1 Main Output Enable */
  TIM_CtrlPWMOutputs(TIM1, ENABLE);
/**********************************配置TIM2捕获TIM1发出固定的PWM信号***************************************/
/* TIM2 channel 1 pin (PE.11) configuration */
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_15;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* Connect TIM pins to AF2 */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource15, GPIO_AF_2);


TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period = 65535; // Set full 16-bit working range
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);

  TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
  TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
  TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  TIM_ICInitStructure.TIM_ICFilter = 0x0;
  TIM_ICInit(TIM2, &TIM_ICInitStructure);

  /* TIM enable counter */
  TIM_Cmd(TIM2, ENABLE);
  /* Enable the CC1 Interrupt Request */
  TIM_ITConfig(TIM2, TIM_IT_CC1, ENABLE);

  /* Enable the TIM1 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

}