配置一个I/O为EXTI中断的步骤：

GPIO_InitTypeDefGPIO_InitStructure;

EXTI_InitTypeDefEXTI_InitStructure;

NVIC_InitTypeDefNVIC_InitStructure;

//1.使能EXTIx线的时钟和第二功能AFIO时钟

RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO|RCC_APB2Periph_GPIOA,ENABLE);

//NVIC_CONFIG();

//2.配置EXTIx线的中断优先级

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);

NVIC_InitStructure.NVIC_IRQChannel=EXTI3_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority=0;

NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;

NVIC_Init(&NVIC_InitStructure);

//3.配置EXTIx中断线的I/O口

GPIO_InitStructure.GPIO_Pin=GPIO_Pin_3;

GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IPD;

GPIO_Init(GPIOA,&GPIO_InitStructure);

GPIO_EXTILineConfig(GPIO_PortSourceGPIOA,GPIO_PinSource3);//4.选定要配置为EXTI的I/O口线

//5.EXTIx中断线的工作模式的配置

EXTI_InitStructure.EXTI_Line=EXTI_Line3;

EXTI_InitStructure.EXTI_Mode=EXTI_Mode_Interrupt;

EXTI_InitStructure.EXTI_Trigger=EXTI_Trigger_Falling;

EXTI_InitStructure.EXTI_LineCmd=ENABLE;

EXTI_Init(&EXTI_InitStructure);