明明没有高电平触发，却一直能进EXIT外部中断

安宁和平

GPIO_InitTypeDef   GPIO_InitStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
TIM_ICInitTypeDef  TIM_ICInitStructure;
NVIC_InitTypeDef   NVIC_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
EXTI_InitTypeDef EXTI_InitStructure;

void TIM6_Config(void)
{
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6 , ENABLE);
       
  TIM_TimeBaseStructure.TIM_Prescaler = 16800 - 1;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = 5000;   
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
  TIM_TimeBaseInit(TIM6, &TIM_TimeBaseStructure);
       
  TIM_ClearITPendingBit(TIM6, TIM_FLAG_Update);
  TIM_ITConfig(TIM6, TIM_FLAG_Update,ENABLE);
  TIM_ITConfig(TIM6, TIM_FLAG_Trigger,ENABLE);
  TIM_Cmd(TIM6, ENABLE);       
       
        NVIC_InitStructure.NVIC_IRQChannel = TIM6_DAC_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_Init(&NVIC_InitStructure);
}

void HCSR04_Init_EXIT(void)
{
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
  SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOE, EXTI_PinSource8);       
       
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;                           
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
  GPIO_Init(GPIOE, &GPIO_InitStructure);

        EXTI_InitStructure.EXTI_Line = EXTI_Line8;
  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;  
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;
  EXTI_Init(&EXTI_InitStructure);
       
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
  NVIC_InitStructure.NVIC_IRQChannel = EXTI9_5_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

安宁和平

答：这是我司一道考题，我在不经意间掉进了这个坑里：
我移植的公司电脑上 STM32F407开发版程序，公司领导知道我今天要做外部中断部分程序，就刻意把我电脑上开发板上外部中断例程中RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);这一句删除了，我比对开发板程序始终没找到原因，刚刚才想到STM32F4外部时钟未打开；
这里要注意M4与M3的差别，M4外部中断时钟不是AFIO，而是SYSCFG。