STM32

输出频率可调的PWM波 一个纠结了好几天的问题

2019-08-23 15:44发布

站内问答 / STM32/STM8
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8下面代码中，为什么重载值是65535啊？  那样的话，按公式计算频率岂不是：72000000/（65536*36）了吗？那又如何实现可调？  我知道我肯定进入了理解误区，但想不通哪里错了，求各位懂的人指点，万分感激！
 u16 capture = 0; 
extern vu16 CCR1_Val; 
extern vu16 CCR2_Val; 
extern vu16 CCR3_Val; 
//extern vu16 CCR4_Val; 
void TIM_Configuration(void) 
{ 
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; 
    TIM_OCInitTypeDef TIM_OCInitStructure; 
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); 

//  TIM_CtrlPWMOutputs(TIM2,ENABLE); 
     


TIM_TimeBaseStructure.TIM_Period = 65535;        
    TIM_TimeBaseStructure.TIM_Prescaler = 35;      
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;  
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure); 

    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;      //PWM模式2 
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //正向通道有效 
    TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;//反向通道无效 
    TIM_OCInitStructure.TIM_Pulse = CCR1_Val;        //占空时间 
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;    //输出极性 
    TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;    //互补端的极性 
    TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set; 
    TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset; 

    TIM_OC1Init(TIM2,&TIM_OCInitStructure);        //通道1 
    TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Disable); 


TIM_OCInitStructure.TIM_Pulse = CCR2_Val;        //占空时间 
    TIM_OC2Init(TIM2,&TIM_OCInitStructure);        //通道2 
    TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Disable); 

    TIM_OCInitStructure.TIM_Pulse = CCR3_Val;        //占空时间 
    TIM_OC3Init(TIM2,&TIM_OCInitStructure);        //通道3 
    TIM_OC3PreloadConfig(TIM2, TIM_OCPreload_Disable);

    TIM_Cmd(TIM2,ENABLE); 
//  TIM_CtrlPWMOutputs(TIM2,ENABLE); 
    TIM_ITConfig(TIM2, TIM_IT_CC1 | TIM_IT_CC2| TIM_IT_CC3 , ENABLE); 
} 
void GPIO_Configuration(void) 
{ 
     GPIO_InitTypeDef GPIO_InitStructure; 
     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); 

     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_1| GPIO_Pin_0 ; 
     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; 
     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 

     GPIO_Init(GPIOA, &GPIO_InitStructure); 
} 
void WM_Init(void) 
{   
   NVIC_InitTypeDef NVIC_InitStructure; 
 NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1); 
     NVIC_InitStructure.NVIC_IRQChannel=TIM2_IRQn; 
     NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0; 
     NVIC_InitStructure.NVIC_IRQChannelSubPriority=1; 
     NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;  
     NVIC_Init(&NVIC_InitStructure); 
     TIM_Configuration(); 
 GPIO_Configuration(); 
} 

void TIM2_IRQHandler(void) 
{ 


   if (TIM_GetITStatus(TIM2, TIM_IT_CC1) != RESET) 
   { 
      TIM_ClearITPendingBit(TIM2, TIM_IT_CC1 ); 
      capture = TIM_GetCapture1(TIM2); 
      TIM_SetCompare1(TIM2, capture + CCR1_Val ); 
    } 
   if (TIM_GetITStatus(TIM2, TIM_IT_CC2) != RESET) 
   { 
      TIM_ClearITPendingBit(TIM2, TIM_IT_CC2); 
      capture = TIM_GetCapture2(TIM2); 
      TIM_SetCompare2(TIM2, capture + CCR2_Val); 
    }
   if (TIM_GetITStatus(TIM2, TIM_IT_CC3) != RESET) 
   { 
      TIM_ClearITPendingBit(TIM2, TIM_IT_CC3 ); 
      capture = TIM_GetCapture3(TIM2); 
      TIM_SetCompare3(TIM2, capture + CCR3_Val ); 
    }    


}
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8条回答
rgzdb
2019-08-24 09:00
 精彩回答 2  元偷偷看……0人看过

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