关于STM32 PWM捕获模式

只看该作者 · 2012-5-9 19:37

/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 65535;
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
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(TIM3, &TIM_ICInitStructure);
  TIM_PWMIConfig(TIM3, &TIM_ICInitStructure);                //根据参数配置TIM外设信息
TIM_SelectInputTrigger(TIM3, TIM_TS_TI2FP2);             //选择IC2为始终触发源
   TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset);//TIM从模式：触发信号的上升沿重新初始化计数器和触发寄存器的更新事件
   TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable); //启动定时器的被动触发

/* PWM1 Mode configuration: Channel3 */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = CCR3_Val;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM3, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);

TIM_ARRPreloadConfig(TIM3, ENABLE);
/* TIM3 enable counter */
TIM_Cmd(TIM3, ENABLE);
  /* Enable the CC2 Interrupt Request */
   TIM_ITConfig(TIM3, TIM_IT_CC2, ENABLE);

void TIM3_IRQHandler(void)
{
if(TIM_GetITStatus(TIM3, TIM_IT_CC2) == SET)
{
   /* Clear TIM3 Capture compare interrupt pending bit */
   TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);
   if(CaptureNumber == 0)
   {
   USART_SendData(USART1, TIM3 -> CNT);
while(USART_GetFlagStatus(USART1, USART_FLAG_TC)==RESET);
      /* Get the Input Capture value */
      IC3ReadValue1 = TIM_GetCapture2(TIM3);
   USART_SendData(USART1, IC3ReadValue1);
while(USART_GetFlagStatus(USART1, USART_FLAG_TC)==RESET);
TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;
      CaptureNumber = 1;
   }
   else if(CaptureNumber == 1)
   {
      /* Get the Input Capture value */
      IC3ReadValue2 = TIM_GetCapture1(TIM3);
TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
CaptureNumber = 2;
  }
  else if(CaptureNumber == 2)
  {

IC3ReadValue3 = TIM_GetCapture2(TIM3);
      /* Capture computation */
      if (IC3ReadValue3 > IC3ReadValue1)
      {
      Capture = (IC3ReadValue3 - IC3ReadValue1);
      }
      else
      {
      Capture = ((0xFFFF - IC3ReadValue1) + IC3ReadValue3);
}
      /* Frequency computation */
capture = (IC3ReadValue2 - IC3ReadValue1)*100/ Capture;
      //TIM3Freq = (u32) 72000000 / Capture;
      CaptureNumber = 0;
   }
}

以上是我的捕获代码，但是每次从IC3ReadValue3、IC3ReadValue1这两个值都是3，不知道是怎么回事

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