1、概述

STM32的每個IO都可以作為外部中斷輸入。
STM32的中斷控制器支援19個外部中斷/事件請求：

• 線0~15：對應外部IO口的輸入中斷。
• 線16：連線到PVD輸出。
• 線17：連線到RTC鬧鐘事件。

• 線18：連線到USB喚醒事件。

  1）引腳與中斷線對應關係

  STM32F103有112個IO，但是中斷線只有16個，中斷線按如下方式與IO對應：我們知道STM32F103有7組IO，即GPIOA、GPIOB、…、GPIOG，每一組有16個引腳，如GPIOA0、GPIOA1、…、GPIOA15，因此STM32F103是按引腳分類為16組對應到16箇中斷線上，如下圖：
  
  即：GPIOx.0對映到EXTI0、GPIOx.1對映到EXTI1、…、GPIOx.15對映到EXTI15。

2）外部中斷服務函式

STM32的IO外部中斷函式只有6個，如下：

EXPORT EXTI0_IRQHandler           
EXPORT EXTI1_IRQHandler
EXPORT EXTI2_IRQHandler           
EXPORT EXTI3_IRQHandler           
EXPORT EXTI4_IRQHandler           
EXPORT EXTI9_5_IRQHandler         
EXPORT EXTI15_10_IRQHandler

中斷線0~4每個中斷線對應一箇中斷函式，中斷線5~9共用中斷函式EXTI9_5_IRQHandler，中斷線10~15共用中斷函式EXTI15_10_IRQHandler。
中斷函式使用示例如下：

void EXTI3_IRQHandler(void){
    if(EXTI_GetITStatus(EXIT_Line3)!=RESET){//判斷某個線上的中斷是否發生
        ...
        EXTI_ClearITPendingBit(EXTI_Line3);//清除LINE上的中斷標誌位
    }
}

3）外部中斷編寫步驟

①初始化IO口為輸入。
GPIO_Init();
② 開啟IO口複用時鐘。
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);
②設定IO口與中斷線的對映關係。
void GPIO_EXTILineConfig();
③初始化線上中斷，設定觸發條件等。
EXTI_Init();
④配置中斷分組（NVIC），並使能中斷。
NVIC_Init();
⑤編寫中斷服務函式。
EXTIx_IRQHandler();
⑥清除中斷標誌位
EXTI_ClearITPendingBit();

4）有關外部中斷的相關變數定義

stm32f10x_exti.h

typedef enum
{
  EXTI_Mode_Interrupt = 0x00,
  EXTI_Mode_Event = 0x04
}EXTIMode_TypeDef;

#define IS_EXTI_MODE(MODE) (((MODE) == EXTI_Mode_Interrupt) || ((MODE) == EXTI_Mode_Event))

typedef enum
{
  EXTI_Trigger_Rising = 0x08,
  EXTI_Trigger_Falling = 0x0C,  
  EXTI_Trigger_Rising_Falling = 0x10
}EXTITrigger_TypeDef;

#define IS_EXTI_TRIGGER(TRIGGER) (((TRIGGER) == EXTI_Trigger_Rising) || \
                                  ((TRIGGER) == EXTI_Trigger_Falling) || \
                                  ((TRIGGER) == EXTI_Trigger_Rising_Falling))

typedef struct
{
  uint32_t EXTI_Line;               /*!< Specifies the EXTI lines to be enabled or disabled.
                                         This parameter can be any combination of @ref EXTI_Lines */

  EXTIMode_TypeDef EXTI_Mode;       /*!< Specifies the mode for the EXTI lines.
                                         This parameter can be a value of @ref EXTIMode_TypeDef */

  EXTITrigger_TypeDef EXTI_Trigger; /*!< Specifies the trigger signal active edge for the EXTI lines.
                                         This parameter can be a value of @ref EXTIMode_TypeDef */

  FunctionalState EXTI_LineCmd;     /*!< Specifies the new state of the selected EXTI lines.
                                         This parameter can be set either to ENABLE or DISABLE */ 
}EXTI_InitTypeDef;

#define EXTI_Line0       ((uint32_t)0x00001)  /*!< External interrupt line 0 */
#define EXTI_Line1       ((uint32_t)0x00002)  /*!< External interrupt line 1 */
#define EXTI_Line2       ((uint32_t)0x00004)  /*!< External interrupt line 2 */
#define EXTI_Line3       ((uint32_t)0x00008)  /*!< External interrupt line 3 */
#define EXTI_Line4       ((uint32_t)0x00010)  /*!< External interrupt line 4 */
#define EXTI_Line5       ((uint32_t)0x00020)  /*!< External interrupt line 5 */
#define EXTI_Line6       ((uint32_t)0x00040)  /*!< External interrupt line 6 */
#define EXTI_Line7       ((uint32_t)0x00080)  /*!< External interrupt line 7 */
#define EXTI_Line8       ((uint32_t)0x00100)  /*!< External interrupt line 8 */
#define EXTI_Line9       ((uint32_t)0x00200)  /*!< External interrupt line 9 */
#define EXTI_Line10      ((uint32_t)0x00400)  /*!< External interrupt line 10 */
#define EXTI_Line11      ((uint32_t)0x00800)  /*!< External interrupt line 11 */
#define EXTI_Line12      ((uint32_t)0x01000)  /*!< External interrupt line 12 */
#define EXTI_Line13      ((uint32_t)0x02000)  /*!< External interrupt line 13 */
#define EXTI_Line14      ((uint32_t)0x04000)  /*!< External interrupt line 14 */
#define EXTI_Line15      ((uint32_t)0x08000)  /*!< External interrupt line 15 */
#define EXTI_Line16      ((uint32_t)0x10000)  /*!< External interrupt line 16 Connected to the PVD Output */
#define EXTI_Line17      ((uint32_t)0x20000)  /*!< External interrupt line 17 Connected to the RTC Alarm event */
#define EXTI_Line18      ((uint32_t)0x40000)  /*!< External interrupt line 18 Connected to the USB Device/USB OTG FS
                                                   Wakeup from suspend event */                                    
#define EXTI_Line19      ((uint32_t)0x80000)  /*!< External interrupt line 19 Connected to the Ethernet Wakeup event */

#define IS_EXTI_LINE(LINE) ((((LINE) & (uint32_t)0xFFF00000) == 0x00) && ((LINE) != (uint16_t)0x00))
#define IS_GET_EXTI_LINE(LINE) (((LINE) == EXTI_Line0) || ((LINE) == EXTI_Line1) || \
                            ((LINE) == EXTI_Line2) || ((LINE) == EXTI_Line3) || \
                            ((LINE) == EXTI_Line4) || ((LINE) == EXTI_Line5) || \
                            ((LINE) == EXTI_Line6) || ((LINE) == EXTI_Line7) || \
                            ((LINE) == EXTI_Line8) || ((LINE) == EXTI_Line9) || \
                            ((LINE) == EXTI_Line10) || ((LINE) == EXTI_Line11) || \
                            ((LINE) == EXTI_Line12) || ((LINE) == EXTI_Line13) || \
                            ((LINE) == EXTI_Line14) || ((LINE) == EXTI_Line15) || \
                            ((LINE) == EXTI_Line16) || ((LINE) == EXTI_Line17) || \
                            ((LINE) == EXTI_Line18) || ((LINE) == EXTI_Line19))

void EXTI_DeInit(void);
void EXTI_Init(EXTI_InitTypeDef* EXTI_InitStruct);
void EXTI_StructInit(EXTI_InitTypeDef* EXTI_InitStruct);
void EXTI_GenerateSWInterrupt(uint32_t EXTI_Line);
FlagStatus EXTI_GetFlagStatus(uint32_t EXTI_Line);
void EXTI_ClearFlag(uint32_t EXTI_Line);
ITStatus EXTI_GetITStatus(uint32_t EXTI_Line);
void EXTI_ClearITPendingBit(uint32_t EXTI_Line);

2、外部中斷示例程式碼

本示例程式碼實現的功能是按按鍵1 板子上的的兩個LED燈的 交替亮，硬體連線圖如下：

從上圖中我們知道PE2接KEY3、PE3接KEY2、PE3接KEY1、PE5接LED1、PB5接LED0

程式碼如下：

staitc bool isLed0Light=true;

void Base_Init(void)
{

    EXTI_InitTypeDef EXTI_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;

    //  按鍵埠初始化
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOE,ENABLE);//使能PORTA,PORTE時鐘

    GPIO_InitStructure.GPIO_Pin  = GPIO_Pin_3;//KEY3
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; //設定成上拉輸入
    GPIO_Init(GPIOE, &GPIO_InitStructure);//初始化GPIOE3

    //LED初始化    
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB|RCC_APB2Periph_GPIOE, ENABLE);   //使能PB,PE埠時鐘

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;                //LED0-->PB.5 埠配置
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;         //推輓輸出
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;        //IO口速度為50MHz
    GPIO_Init(GPIOB, &GPIO_InitStructure);                   //根據設定引數初始化GPIOB.5
    GPIO_SetBits(GPIOB,GPIO_Pin_5);                      //PB.5 輸出高

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;                //LED1-->PE.5 埠配置, 推輓輸出
    GPIO_Init(GPIOE, &GPIO_InitStructure);                   //推輓輸出 ，IO口速度為50MHz
    GPIO_SetBits(GPIOE,GPIO_Pin_5);                          //PE.5 輸出高 
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE); //使能複用功能時鐘

    //GPIOE.3     中斷線以及中斷初始化配置 下降沿觸發 //KEY1
    GPIO_EXTILineConfig(GPIO_PortSourceGPIOE,GPIO_PinSource3);
    EXTI_InitStructure.EXTI_Line=EXTI_Line3;
    EXTI_Init(&EXTI_InitStructure);     //根據EXTI_InitStruct中指定的引數初始化外設EXTI暫存器

    EXTI_InitStructure.EXTI_Line=EXTI_Line3;    //KEY1
    EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt; 
    EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
    EXTI_InitStructure.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStructure);     //根據EXTI_InitStruct中指定的引數初始化外設EXTI暫存器

    NVIC_InitStructure.NVIC_IRQChannel = EXTI3_IRQn;            //使能按鍵KEY1所在的外部中斷通道
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x02;    //搶佔優先順序2 
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x01;                   //子優先順序1 
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;                             //使能外部中斷通道
    NVIC_Init(&NVIC_InitStructure);       //根據NVIC_InitStruct中指定的引數初始化外設NVIC暫存器 
}

//外部中斷3服務程式
void EXTI3_IRQHandler(void)
{
    delay_ms(10);//消抖
    uint8_t KEY1 = GPIO_ReadInputDataBit(GPIOE,GPIO_Pin_3)//讀取按鍵1
    if(KEY1==0)  //按鍵KEY1，因為由按鍵電路圖知當鍵按下時微控制器接到的是低電平，所以KEY1==0表示按下KEY1
    {
        if(isLed0Light){
            isLed0Light = !isLed0Light;
            GPIO_SetBits(GPIOE, GPIO_Pin_5);//LED1點亮
            GPIO_ResetBits(GPIOB, GPIO_Pin_5);//LED0熄滅
        }else{
            GPIO_SetBits(GPIOB, GPIO_Pin_5);//LED0點亮
            GPIO_ResetBits(GPIOE, GPIO_Pin_5);//LED1熄滅
        }
    }        
    EXTI_ClearITPendingBit(EXTI_Line3);  //清除LINE3上的中斷標誌位  
}