STM32F401的外部中断EXTI

stm32f401 EXTI

EXTI就是External interrupt/event controller, 外部事件和中断控制器, 包含21条边沿检测线. 每条线可以独立设置触发事件(上升沿, 下降沿或两者同时). 一个等待寄存器维护中断请求的状态.

当动作发生(例如按键按下)时, 如果电平状态由低变高, 会在输入线产生一个上升沿信号, 这个信号到达边沿检测电路后, 会被上升沿触发选择寄存器(EXTI_RTSR)检测并触发, 输出有效信号, 否则输出无效信号0. 反之如果电平由高变低, 则会被下降沿触发选择寄存器(EXTI_FTSR)检测触发.

EXTI可以在外部连线上检测到比内部APB2时钟周期更短的脉冲. stm32f4系列最多有81个GPIO可以连接到16个外部中断线. IO口和中断线的映射是多对一的, 例如EXTI0, 可以对应PA0, PB0, PC0等, 实际用到某个I/O引脚时, 通过配置决定具体哪个引脚对应EXTI0.

在stm32f4xx_exti.h中定义了0 - 23的中断线

#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 OTG FS Wakeup from suspend event */
#define EXTI_Line19      ((uint32_t)0x80000)     /*!< External interrupt line 19 Connected to the Ethernet Wakeup event */
#define EXTI_Line20      ((uint32_t)0x00100000)  /*!< External interrupt line 20 Connected to the USB OTG HS (configured in FS) Wakeup event  */
#define EXTI_Line21      ((uint32_t)0x00200000)  /*!< External interrupt line 21 Connected to the RTC Tamper and Time Stamp events */
#define EXTI_Line22      ((uint32_t)0x00400000)  /*!< External interrupt line 22 Connected to the RTC Wakeup event */
#define EXTI_Line23      ((uint32_t)0x00800000)  /*!< External interrupt line 23 Connected to the LPTIM Wakeup event */

在stm32f4xx.h中, 有这些中断的常量, 注意: Line虽然是各自独立的, 但是IRQn不是, Handler也不是

  EXTI0_IRQn                  = 6,      /*!< EXTI Line0 Interrupt                                              */
  EXTI1_IRQn                  = 7,      /*!< EXTI Line1 Interrupt                                              */
  EXTI2_IRQn                  = 8,      /*!< EXTI Line2 Interrupt                                              */
  EXTI3_IRQn                  = 9,      /*!< EXTI Line3 Interrupt                                              */
  EXTI4_IRQn                  = 10,     /*!< EXTI Line4 Interrupt                                              */
  EXTI9_5_IRQn                = 23,     /*!< External Line[9:5] Interrupts                                     */
  EXTI15_10_IRQn              = 40,     /*!< External Line[15:10] Interrupts                                   */

可以看到, 对于EXTI0到EXTI4(Line0到Line4), 都是单独的常量, 而Line5到Line9, Line10到Line15都是合用的.

对应的, 有以下的中断处理方法, 通过这些方法将自己的中断逻辑关联到对应的中断事件上去

EXTI0_IRQHandler
EXTI1_IRQHandler
EXTI2_IRQHandler
EXTI3_IRQHandler
EXTI4_IRQHandler
EXTI9_5_IRQHandler
EXTI15_10_IRQHandler

初始化的步骤

                       ##### How to use this driver #####
 ==================================================

 [..] In order to use an I/O pin as an external interrupt source, follow steps
      below:
   (#) Configure the I/O in input mode using GPIO_Init()
   (#) Select the input source pin for the EXTI line using SYSCFG_EXTILineConfig()
   (#) Select the mode(interrupt, event) and configure the trigger
       selection (Rising, falling or both) using EXTI_Init()
   (#) Configure NVIC IRQ channel mapped to the EXTI line using NVIC_Init()

 [..]
   (@) SYSCFG APB clock must be enabled to get write access to SYSCFG_EXTICRx
       registers using RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

1. 使能I/O口时钟, 初始化I/O口为输入
2. 使能SYSCFG时钟, 设置I/O口与中断线的映射关系
3. 初始化中断线(EXTI线编号, 中断模式是中断还是事件, 触发方式是下降沿触发、上升沿触发还是任意电平触发, 是否使能中断线)
4. 配置嵌套中断向量控制器NVIC
5. 编写中断服务函数 对应各个中断线分别有EXTI0_IRQHandler(), EXTI1_IRQHandler(), ... EXTI9_5_IRQHandler(), EXTI15_10_IRQHandler().

官方的代码例子

• This example shows how to configure external interrupt lines.
• In this example, 2 EXTI lines (EXTI Line0 and Line15) are configured to generate an interrupt on each rising and falling edge, respectively.
• In the interrupt routine a LED connected to a specific GPIO pin is toggled.

static void EXTILine0_Config(void);
static void EXTILine13_15_Config(void);

/* Private functions ---------------------------------------------------------*/

/**
  * @brief  Main program
  * @param  None
  * @retval None
  */
int main(void)
{
  /* Initialize LEDs mounted on EVAL board */
  STM_EVAL_LEDInit(LED1);
  STM_EVAL_LEDInit(LED2);

  /* Configure EXTI Line0 (connected to PA0 pin) in interrupt mode */
  EXTILine0_Config();

  /* Configure EXTI Line13/15 (connected to PG13/15 pin) in interrupt mode
     according to EVAL used */
  EXTILine13_15_Config();

  /* Generate software interrupt: simulate a falling edge applied on EXTI0 line */
  EXTI_GenerateSWInterrupt(EXTI_Line0);

  while (1)
  {
  }
}

/**
  * @brief  Configures EXTI Line0 (connected to PA0 pin) in interrupt mode
  * @param  None
  * @retval None
  */
static void EXTILine0_Config(void)
{
  EXTI_InitTypeDef   EXTI_InitStructure;
  GPIO_InitTypeDef   GPIO_InitStructure;
  NVIC_InitTypeDef   NVIC_InitStructure;

  /* Enable GPIOA clock */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
  /* Enable SYSCFG clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

  /* Configure PA0 pin as input floating */
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* Connect EXTI Line0 to PA0 pin */
  SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource0);

  /* Configure EXTI Line0 */
  EXTI_InitStructure.EXTI_Line = EXTI_Line0;
  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;
  EXTI_Init(&EXTI_InitStructure);

  /* Enable and set EXTI Line0 Interrupt to the lowest priority */
  NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x0F;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x0F;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

/**
  * @brief  Configures EXTI Line15 (connected to PG15 pin) in interrupt mode
  * @param  None
  * @retval None
  */
static void EXTILine13_15_Config(void)
{
  EXTI_InitTypeDef   EXTI_InitStructure;
  GPIO_InitTypeDef   GPIO_InitStructure;
  NVIC_InitTypeDef   NVIC_InitStructure;

#ifdef USE_STM324x9I_EVAL
  /* Enable GPIOC clock */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
#else
  /* Enable GPIOG clock */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOG, ENABLE);
#endif /* USE_STM324x9I_EVAL */

  /* Enable SYSCFG clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

  /* Configure PG15 pin as input floating */
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
#ifdef USE_STM324x9I_EVAL
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
#else
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_15;
  GPIO_Init(GPIOG, &GPIO_InitStructure);
#endif /* USE_STM324x9I_EVAL */  

  /* Connect EXTI Line15 to PG15 pin */
#ifdef USE_STM324x9I_EVAL
  SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOC, EXTI_PinSource13);
#else
  SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOG, EXTI_PinSource15);
#endif /* USE_STM324x9I_EVAL */  

  /* Configure EXTI Line15 */
#ifdef USE_STM324x9I_EVAL
  EXTI_InitStructure.EXTI_Line = EXTI_Line13;
#else
  EXTI_InitStructure.EXTI_Line = EXTI_Line15;
#endif /* USE_STM324x9I_EVAL */  

  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;
  EXTI_Init(&EXTI_InitStructure);

  /* Enable and set EXTI15_10 Interrupt to the lowest priority */
  NVIC_InitStructure.NVIC_IRQChannel = EXTI15_10_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x0F;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x0F;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

  NVIC_Init(&NVIC_InitStructure);
}

处理中断的例子

中断处理, 涉及的就是三步: 1)消抖(如果是按键触发), 2)确认中断源, 3)清除中断标志位

// 1
void EXTI4_IRQHandler( void )
{
  delay_ms( 10 ); /* 消抖 */
  if ( GPIO_ReadInputDataBit( GPIOE, GPIO_Pin_4 ) == 0 ) {
    GPIO_ResetBits(GPIOF,GPIO_Pin_9);//输出低电平，灯亮
  }
  /* 清除LINE4上的中断标志位 */
  EXTI_ClearITPendingBit( EXTI_Line4 );
}

// 2
void EXTI0_IRQHandler(void)
{
  if(EXTI_GetITStatus(EXTI_Line0) != RESET) {} // 确保产生了EXTI0线中断
    LED_TOGGLE; // LED灯状态切换
    EXTI_ClearITPendingBit(EXTI_Line0);// 清除中断标志位
  }
}

// 3
/* Set interrupt handlers */
/* Handle PB12 interrupt */
void EXTI15_10_IRQHandler(void) {
  /* Make sure that interrupt flag is set */
  if (EXTI_GetITStatus(EXTI_Line12) != RESET) {
    /* Do your stuff when PB12 is changed */

    /* Clear interrupt flag */
    EXTI_ClearITPendingBit(EXTI_Line12);
  }
}

参考

• https://stm32f4-discovery.net/2014/08/stm32f4-external-interrupts-tutorial/