定时器的PWM捕获问题

djqlyy

STM32F407VGT6
TIM3_CH3(PB0)作为PWM输出 （此路正常工作）
TIM3_CH1(PB4)作为PWM输入捕获(此路工作不正常)
配置信息如下： GPIO_InitTypeDef GPIO_InitStructure; TIM_ICInitTypeDef TIM_ICInitStructure; RCC_AHB1PeriphClockCmd( RCC_AHB1Periph_GPIOB, ENABLE); GPIO_PinAFConfig(GPIOB,GPIO_PinSource4,GPIO_AF_TIM3); GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; GPIO_Init(GPIOB, &GPIO_InitStructure); RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE); TIM_ICInitStructure.TIM_Channel = TIM_Channel_1; TIM_ICInitStructure.TIM_ICPolarity =TIM_ICPolarity_Rising; TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1; TIM_ICInitStructure.TIM_ICFilter = 0x0; TIM_PWMIConfig(TIM3, &TIM_ICInitStructure); TIM_SelectInputTrigger(TIM3, TIM_TS_TI1FP1); TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset); TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable); TIM_Cmd(TIM3, ENABLE); 运行中，只有CCR2中有正确的脉宽值，CCR1中应有的PWM周期值一直为0，不知道是什么原因！！！