目的： PB0作为外部中断IO口，当低电平时进入中断通过串口发送字符串
配置如下 ：IO配置如下  #define         Shi_0                                GPIO_Pin_0
        GPIO_InitTypeDef  GPIO_InitStructure;
       
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB);
       
        //ÅäÖÃADS_DR pb0
  GPIO_InitStructure.GPIO_Pin =Shi_0;
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;//¸′
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;//100MHz
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;//
  GPIO_Init(GPIOB, &GPIO_InitStructure);//


void EXTIX_Init(void)
{
        NVIC_InitTypeDef   NVIC_InitStructure;
        EXTI_InitTypeDef   EXTI_InitStructure;
       
       
  GPIO_Init();//初始化IO
       
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);//ê1ÄüSYSCFGê±Öó
       



        SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOB, EXTI_PinSource0);//Pb0 ᬽóμ½ÖD¶ÏÏß0
//       
  /* ÅäÖÃEXTI_Line0 */
  EXTI_InitStructure.EXTI_Line = EXTI_Line0;//LINE0
  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;//ÖD¶Ïê¼t
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling; //ϽμÑØ′￥·￠
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;//ê1ÄüLINE0
  EXTI_Init(&EXTI_InitStructure);//ÅäÖÃ

       
        NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;//ía2¿ÖD¶Ï0
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00;//ÇàÕ¼óÅÏ輶0
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x02;//×óóÅÏ輶2
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;//ê1Äüía2¿ÖD¶Ïí¨μà
  NVIC_Init(&NVIC_InitStructure);//ÅäÖÃ
}

void EXTI0_IRQHandler(void)
{
           if(Shi_0==0)         
        {
                printf("进入中断 “);
        }
        printf("发送 “);
         EXTI_ClearITPendingBit(EXTI_Line0); //Çå3yLINE0éÏμÄÖD¶Ï±ê־λ
}       


串口发送可以用已调试，我用的下降沿出发；用导线的一头接触GND当程序跑起来串口显示“发送”无法进入if语句求大神们给解释下