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）;