stm32系列--PWM捕获功能

 

 

Capture_Init(59999,120-1);  // 可捕获最小频率 72M/(120*60000)= 17*0.6=10Hz  PA1

// TIM2_CH2  PA7 做为捕获通道 
// 输入捕获能捕获到的最小的频率为 72M/{ (ARR+1)*(PSC+1) }
void Capture_Init(u16 arr, u16 psc)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitSturcture;
    TIM_ICInitTypeDef TIM_ICInitSturcture;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD;//GPIO_Mode_IN_FLOATING
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    TIM_TimeBaseInitSturcture.TIM_Period = arr;
    TIM_TimeBaseInitSturcture.TIM_Prescaler = psc;
    TIM_TimeBaseInitSturcture.TIM_ClockDivision = TIM_CKD_DIV1;                                                                       
    TIM_TimeBaseInitSturcture.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitSturcture);

    TIM_ICInitSturcture.TIM_Channel = TIM_Channel_2;
    TIM_ICInitSturcture.TIM_ICFilter = 0x0f; //0x00
    TIM_ICInitSturcture.TIM_ICPolarity = TIM_ICPolarity_Rising;
    TIM_ICInitSturcture.TIM_ICPrescaler = TIM_ICPSC_DIV1;
    TIM_ICInitSturcture.TIM_ICSelection = TIM_ICSelection_DirectTI;
    //TIM_ICInit(TIM2, &TIM_ICInitSturcture);

    TIM_PWMIConfig(TIM2, &TIM_ICInitSturcture);            //初始化PWM输入模式
    // 当工作做PWM输入模式时,只需要设置触发信号的那一路即可（用于测量周期）
    // 另外一路（用于测量占空比）会由硬件自带设置，不需要再配置

    TIM_SelectInputTrigger(TIM2, TIM_TS_TI2FP2);            //选择输入捕获触发信号
    TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Reset);       // PWM输入模式时,从模式必须工作在复位模式，当捕获开始时,计数器CNT会被复位
    TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);


    NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x02;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x02;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    TIM_ITConfig(TIM2, TIM_IT_CC2, ENABLE);          // 使能捕获中断,这个中断针对的是主捕获通道（测量周期那个）
    TIM_Cmd(TIM2, ENABLE);
}

//float DutyCycle = 0;
//float Frequency  = 0;
u32  DutyCycle = 0;
u32  Frequency  = 0;
u32 IC1Value = 0;
u32 IC2Value = 0;
//
 // 如果是第一个上升沿中断，计数器会被复位，锁存到CCR1寄存器的值是0，CCR2寄存器的值也是0，
 // 无法计算频率和占空比。当第二次上升沿到来的时候，CCR1和CCR2捕获到的才是有效的值。其中
 // CCR1对应的是周期，CCR2对应的是占空比。
 //
void TIM2_IRQHandler(void)
{
 

    IC1Value = TIM_GetCapture1(TIM2);        // 占空比
    IC2Value = TIM_GetCapture2(TIM2);        // 总长度

      if( myusart.reflag==0)
        {    
            if(IC1Value != 0 && (IC2Value>IC1Value))
            {
                DutyCycle = ((IC1Value + 1) * 10000) / (IC2Value + 1); //5050  50.5%
                Frequency = 600000 / (IC2Value + 1);
            }
            else
            {
                DutyCycle = 0;
                Frequency = 0;
            }        
    }    
    
        TIM_ClearITPendingBit(TIM2,  TIM_IT_CC2);
}