输出频率可调的PWM波一个纠结了好几天的问题 - 平头弟

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

6644 8

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

1楼-- · 2019-08-23 20:03

精彩回答 2 元偷偷看……

2楼-- · 2019-08-24 01:02

自己顶一个

3楼-- · 2019-08-24 05:54

看到代码头就大了，虽然我也不会，但还是顶一个，希望你早日解决问题

4楼-- · 2019-08-24 06:47

TIM_TimeBaseStructure.TIM_Period = 65535;
就是这句搞不懂

5楼-- · 2019-08-24 08:15

回复【5楼】rgzdb:
---------------------------------
回复【5楼】rgzdb:

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle; //PWM模式2 这个不是PWM模式，是输出比较模式中的翻转模式，计数器值与CCRx_Val匹配时翻转OCx的输出引脚获得占空比为50%的波形，频率通过改变CCRx_Val值可以调但占空比不变，TIM_TimeBaseStructure.TIM_Period = 65535这句并不决定输出脚的频率，只要大于CCRx_Val值即可。

---------------------------------
CCRX_Val 不是调节占空比的吗？在这里为什么能调节频率？
谢谢你了

6楼-- · 2019-08-24 09:00

精彩回答 2 元偷偷看……

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