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 提问时间：2009-6-9 09:24 /

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);

}

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2个回答

hebsjx 回答时间：2010-7-20 15:20:38

回复:STM32使用捕获功能，计算输入PWM信号周期，误差很大，求帮忙？？

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);

}

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hebsjx 回答时间：2010-7-20 15:21:57

回复:STM32使用捕获功能，计算输入PWM信号周期，误差很大，求帮忙？？

Prescaler = 18: 分频为19 .

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