STM32使用捕获功能，计算输入PWM信号周期，误差很大，求帮忙？？

studentzf972-93

我用的TIMER2的CH1通道，PWM信号接在PA0脚。我输入100Hz信号，根据捕获得到的结果是105Hz,这误差也太大了吧！！求各位高手帮忙解决一下，万分感谢！！
下面是我的初始化程序：
    1：时钟初始化，我的TIMER2上的时钟频率为36M
      RCC_PCLK1Config(RCC_HCLK_Div2);           //设置低速AHB时钟=系统时钟/2
      RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);    //倍频系数为9  PLLCLK=8*9=72
   
    2：TIMER2初始化
   TIM_DeInit(TIM2);
   TIM_TimeBaseStructure.TIM_Period = 65535;         
   TIM_TimeBaseStructure.TIM_Prescaler = 18;      
   TIM_TimeBaseStructure.TIM_ClockDivision = 0;   
   TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
   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_DIV4;
   TIM_ICInitStructure.TIM_ICFilter = 0x0;
   TIM_PWMIConfig(TIM2, &TIM_ICInitStructure);
  
   TIM_SelectInputTrigger(TIM2, TIM_TS_TI1FP1);
   TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Reset);                       //复位模式为从模式
   TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);          //使能主从模式
 
   TIM_Cmd(TIM2, ENABLE);                           //使能TIM2计数器
   TIM_ITConfig(TIM2, TIM_IT_CC2, ENABLE);          //使能CC2中断请求
 
   3，中断部分程序
   void TIM2_IRQHandler(void)
{
  /* Clear TIM2 Capture compare interrupt pending bit */
  TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);
 
  /* Get the Input Capture value */
  IC2_Value = TIM_GetCapture2(TIM2);
 
}
 

hebsjx

回复第 1 楼 studentzf972于2009-06-09 01:24:10发表:
我用的TIMER2的CH1通道，PWM信号接在PA0脚。我输入100Hz信号，根据捕获得到的结果是105Hz,这误差也太大了吧！！求各位高手帮忙解决一下，万分感谢！！
下面是我的初始化程序：
    1：时钟初始化，我的TIMER2上的时钟频率为36M
      RCC_PCLK1Config(RCC_HCLK_Div2);           //设置低速AHB时钟=系统时钟/2
      RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);    //倍频系数为9  PLLCLK=8*9=72
   
    2：TIMER2初始化
   TIM_DeInit(TIM2);
   TIM_TimeBaseStructure.TIM_Period = 65535;         
   TIM_TimeBaseStructure.TIM_Prescaler = 18;      
   TIM_TimeBaseStructure.TIM_ClockDivision = 0;   
   TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
   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_DIV4;
   TIM_ICInitStructure.TIM_ICFilter = 0x0;
   TIM_PWMIConfig(TIM2, &TIM_ICInitStructure);
  
   TIM_SelectInputTrigger(TIM2, TIM_TS_TI1FP1);
   TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Reset);                       //复位模式为从模式
   TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);          //使能主从模式
 
   TIM_Cmd(TIM2, ENABLE);                           //使能TIM2计数器
   TIM_ITConfig(TIM2, TIM_IT_CC2, ENABLE);          //使能CC2中断请求
 
   3，中断部分程序
   void TIM2_IRQHandler(void)
{
  /* Clear TIM2 Capture compare interrupt pending bit */
  TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);
 
  /* Get the Input Capture value */
  IC2_Value = TIM_GetCapture2(TIM2);
 
}
 
 

hebsjx

  
Prescaler = 18:  分频为19 .