其中输入捕获的函数是这么写的：
void input_catch(u32 arr,u16 psc){
       
       
        GPIO_InitTypeDef GPIO_InitStructure;
        TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
        TIM_ICInitTypeDef TIM_ICInitStructure;
        NVIC_InitTypeDef NVIC_InitStructure;
       
        //时钟使能
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB,ENABLE);
        RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
        //外设声明
        GPIO_PinAFConfig(GPIOB,GPIO_PinSource0,GPIO_AF_TIM3);
        //GPIO初始化
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
        GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
        GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
        GPIO_InitStructure.GPIO_Speed = GPIO_High_Speed;
        GPIO_Init(GPIOB,&GPIO_InitStructure);
        //定时器基本初始化
        TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
        TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
        TIM_TimeBaseStructure.TIM_Period = arr;
        TIM_TimeBaseStructure.TIM_Prescaler = psc;
        TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);
        //输入捕获相关设置
        TIM_ICInitStructure.TIM_Channel = TIM_Channel_3;
        TIM_ICInitStructure.TIM_ICFilter = 0;
        TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
        TIM_ICInitStructure.TIM_ICPrescaler = psc;
        TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
        TIM_ICInit(TIM3,&TIM_ICInitStructure);
       
        TIM_ITConfig(TIM3,TIM_IT_Update|TIM_IT_CC1,ENABLE);//使能定时器以及输入捕获的中断
       
        TIM_Cmd(TIM3,ENABLE);
       
        NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
       
        NVIC_Init(&NVIC_InitStructure);
}