TIM--不进中断捕获PWM

　　定时器具有输入捕获的功能，常用方法是使能定时器输入捕获中断，当上升/下降沿来临时，触发中断，进而进中断

读取到比较捕获值，但该办法有个限制，需要CPU参与处理，同时如果中断过多的话，可能还会有中断打断的问题。所

以可以采用更高效的办法，那就是用DMA来处理，具体处理思路就是利用捕获的这一DMA触发源，当捕获成功发生后触

发DMA搬运数据捕获寄存器里的数据至buff中。

配置：

1，TIM基础配置（参考EVT中输入捕获例程实现，如若部分配置不理解，参考此链接：https://www.cnblogs.com/wchmcu/p/17798582.html）:

void Input_Capture_Init( u16 arr, u16 psc )
{
    GPIO_InitTypeDef GPIO_InitStructure={0};
    TIM_ICInitTypeDef TIM_ICInitStructure={0};
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure={0};
    NVIC_InitTypeDef NVIC_InitStructure={0};

    RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOA | RCC_APB2Periph_TIM1, ENABLE );

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init( GPIOA, &GPIO_InitStructure);
    GPIO_ResetBits( GPIOA, GPIO_Pin_8 );

    TIM_TimeBaseInitStructure.TIM_Period = arr;
    TIM_TimeBaseInitStructure.TIM_Prescaler = psc;
    TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInitStructure.TIM_RepetitionCounter =  0x00;
    TIM_TimeBaseInit( TIM1, &TIM_TimeBaseInitStructure);

    TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
    TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
    TIM_ICInitStructure.TIM_ICFilter = 0x00;
    TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
    TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;

    TIM_PWMIConfig( TIM1, &TIM_ICInitStructure );

    NVIC_InitStructure.NVIC_IRQChannel = TIM1_CC_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    TIM_SelectInputTrigger( TIM1, TIM_TS_TI1FP1 );
    TIM_SelectSlaveMode( TIM1, TIM_SlaveMode_Reset );
    TIM_SelectMasterSlaveMode( TIM1, TIM_MasterSlaveMode_Enable );

}

 2，DMA配置（主要配置就是数据来源于外设，循环模式等）：

void TIM1_DMA_Init(DMA_Channel_TypeDef *DMA_CHx, u32 ppadr, u32 memadr, u16 bufsize)
{
    DMA_InitTypeDef DMA_InitStructure = {0};

    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

    DMA_DeInit(DMA_CHx);
    DMA_InitStructure.DMA_PeripheralBaseAddr = ppadr;
    DMA_InitStructure.DMA_MemoryBaseAddr = memadr;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = bufsize;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA_CHx, &DMA_InitStructure);

    DMA_Cmd(DMA_CHx, ENABLE);
}

比较捕获寄存器的地址

#define TIM1_CH1CVR_ADDRESS    0x40012C34
#define TIM1_CH2CVR_ADDRESS    0x40012C38

3，main中参数配置（500ms打印一次buff中的值，buff0中是PWM周期，buff1中是占空比）

u16 pbuf[2] = {0};
int main(void)
{
    USART_Printf_Init(115200);
    SystemCoreClockUpdate();
    Delay_Init();
    printf("SystemClk:%d\r\n",SystemCoreClock);
    printf( "ChipID:%08x\r\n", DBGMCU_GetCHIPID() );
    Input_Capture_Init( 0xFFFF, 96-1 );
    TIM1_DMA_Init(DMA1_Channel2, (u32)TIM1_CH1CVR_ADDRESS,  (u32)pbuf, 1);
    TIM1_DMA_Init(DMA1_Channel3, (u32)TIM1_CH2CVR_ADDRESS,  (u32)(pbuf+1), 1);
    TIM_DMACmd(TIM1, TIM_DMA_CC1, ENABLE);
    TIM_DMACmd(TIM1, TIM_DMA_CC2, ENABLE);
    TIM_Cmd( TIM1, ENABLE );

    while(1){

        printf("CH1: %d\r\n",pbuf[0]);
        printf("CH2: %d\r\n",pbuf[1]);
        Delay_Ms(500);
    }
}

测试结果（输入占空比75%，周期10K hz的方波）：

 

至此，测试实验完毕！