108.3.3外部中断相关寄存器

/* ==================== Core\Inc\main.h ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.h
  * @brief          : Header for main.c file.
  *                   This file contains the common defines of the application.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __MAIN_H
#define __MAIN_H

#ifdef __cplusplus
extern "C" {
#endif

/* Includes ------------------------------------------------------------------*/
#include "stm32f1xx_hal.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Exported types ------------------------------------------------------------*/
/* USER CODE BEGIN ET */

/* USER CODE END ET */

/* Exported constants --------------------------------------------------------*/
/* USER CODE BEGIN EC */

/* USER CODE END EC */

/* Exported macro ------------------------------------------------------------*/
/* USER CODE BEGIN EM */

/* USER CODE END EM */

/* Exported functions prototypes ---------------------------------------------*/
void Error_Handler(void);

/* USER CODE BEGIN EFP */

/* USER CODE END EFP */

/* Private defines -----------------------------------------------------------*/
#define EXIT_KEY1_Pin GPIO_PIN_3
#define EXIT_KEY1_GPIO_Port GPIOE
#define EXIT_KEY1_EXTI_IRQn EXTI3_IRQn
#define EXTI_KEY2_Pin GPIO_PIN_4
#define EXTI_KEY2_GPIO_Port GPIOE
#define EXTI_KEY2_EXTI_IRQn EXTI4_IRQn
#define LED1_Pin GPIO_PIN_5
#define LED1_GPIO_Port GPIOB
#define BEEP_Pin GPIO_PIN_8
#define BEEP_GPIO_Port GPIOB

/* USER CODE BEGIN Private defines */

/* USER CODE END Private defines */

#ifdef __cplusplus
}
#endif

#endif /* __MAIN_H */

/* ==================== Core\Inc\gpio.h ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    gpio.h
  * @brief   This file contains all the function prototypes for
  *          the gpio.c file
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __GPIO_H__
#define __GPIO_H__

#ifdef __cplusplus
extern "C" {
#endif

/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* USER CODE BEGIN Private defines */

/* USER CODE END Private defines */

void MX_GPIO_Init(void);

/* USER CODE BEGIN Prototypes */

/* USER CODE END Prototypes */

#ifdef __cplusplus
}
#endif
#endif /*__ GPIO_H__ */


/* ==================== Core\Inc\stm32f1xx_it.h ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    stm32f1xx_it.h
  * @brief   This file contains the headers of the interrupt handlers.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
 ******************************************************************************
  */
/* USER CODE END Header */

/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __STM32F1xx_IT_H
#define __STM32F1xx_IT_H

#ifdef __cplusplus
 extern "C" {
#endif

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Exported types ------------------------------------------------------------*/
/* USER CODE BEGIN ET */

/* USER CODE END ET */

/* Exported constants --------------------------------------------------------*/
/* USER CODE BEGIN EC */

/* USER CODE END EC */

/* Exported macro ------------------------------------------------------------*/
/* USER CODE BEGIN EM */

/* USER CODE END EM */

/* Exported functions prototypes ---------------------------------------------*/
void NMI_Handler(void);
void HardFault_Handler(void);
void MemManage_Handler(void);
void BusFault_Handler(void);
void UsageFault_Handler(void);
void SVC_Handler(void);
void DebugMon_Handler(void);
void PendSV_Handler(void);
void SysTick_Handler(void);
void EXTI3_IRQHandler(void);
void EXTI4_IRQHandler(void);
/* USER CODE BEGIN EFP */

/* USER CODE END EFP */

#ifdef __cplusplus
}
#endif

#endif /* __STM32F1xx_IT_H */

/* ==================== Core\Src\main.c ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "gpio.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/* USER CODE BEGIN 4 */
void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
	HAL_Delay(10);
	if(HAL_GPIO_ReadPin(EXIT_KEY1_GPIO_Port, EXIT_KEY1_Pin)==0)
	{
		HAL_GPIO_TogglePin(BEEP_GPIO_Port, BEEP_Pin);
	}
	if(HAL_GPIO_ReadPin(EXTI_KEY2_GPIO_Port, EXTI_KEY2_Pin)==0)
	{
		HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
	}
}
/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

/* ==================== Core\Src\gpio.c ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    gpio.c
  * @brief   This file provides code for the configuration
  *          of all used GPIO pins.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "gpio.h"

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/*----------------------------------------------------------------------------*/
/* Configure GPIO                                                             */
/*----------------------------------------------------------------------------*/
/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

/** Configure pins as
        * Analog
        * Input
        * Output
        * EVENT_OUT
        * EXTI
*/
void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOE_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_SET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(BEEP_GPIO_Port, BEEP_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pins : PEPin PEPin */
  GPIO_InitStruct.Pin = EXIT_KEY1_Pin|EXTI_KEY2_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);

  /*Configure GPIO pin : PtPin */
  GPIO_InitStruct.Pin = LED1_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(LED1_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : PtPin */
  GPIO_InitStruct.Pin = BEEP_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(BEEP_GPIO_Port, &GPIO_InitStruct);

  /* EXTI interrupt init*/
  HAL_NVIC_SetPriority(EXTI3_IRQn, 5, 0);
  HAL_NVIC_EnableIRQ(EXTI3_IRQn);

  HAL_NVIC_SetPriority(EXTI4_IRQn, 7, 0);
  HAL_NVIC_EnableIRQ(EXTI4_IRQn);

}

/* USER CODE BEGIN 2 */

/* USER CODE END 2 */

/* ==================== Core\Src\stm32f1xx_it.c ==================== */
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    stm32f1xx_it.c
  * @brief   Interrupt Service Routines.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "stm32f1xx_it.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN TD */

/* USER CODE END TD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/* External variables --------------------------------------------------------*/

/* USER CODE BEGIN EV */

/* USER CODE END EV */

/******************************************************************************/
/*           Cortex-M3 Processor Interruption and Exception Handlers          */
/******************************************************************************/
/**
  * @brief This function handles Non maskable interrupt.
  */
void NMI_Handler(void)
{
  /* USER CODE BEGIN NonMaskableInt_IRQn 0 */

  /* USER CODE END NonMaskableInt_IRQn 0 */
  /* USER CODE BEGIN NonMaskableInt_IRQn 1 */
   while (1)
  {
  }
  /* USER CODE END NonMaskableInt_IRQn 1 */
}

/**
  * @brief This function handles Hard fault interrupt.
  */
void HardFault_Handler(void)
{
  /* USER CODE BEGIN HardFault_IRQn 0 */

  /* USER CODE END HardFault_IRQn 0 */
  while (1)
  {
    /* USER CODE BEGIN W1_HardFault_IRQn 0 */
    /* USER CODE END W1_HardFault_IRQn 0 */
  }
}

/**
  * @brief This function handles Memory management fault.
  */
void MemManage_Handler(void)
{
  /* USER CODE BEGIN MemoryManagement_IRQn 0 */

  /* USER CODE END MemoryManagement_IRQn 0 */
  while (1)
  {
    /* USER CODE BEGIN W1_MemoryManagement_IRQn 0 */
    /* USER CODE END W1_MemoryManagement_IRQn 0 */
  }
}

/**
  * @brief This function handles Prefetch fault, memory access fault.
  */
void BusFault_Handler(void)
{
  /* USER CODE BEGIN BusFault_IRQn 0 */

  /* USER CODE END BusFault_IRQn 0 */
  while (1)
  {
    /* USER CODE BEGIN W1_BusFault_IRQn 0 */
    /* USER CODE END W1_BusFault_IRQn 0 */
  }
}

/**
  * @brief This function handles Undefined instruction or illegal state.
  */
void UsageFault_Handler(void)
{
  /* USER CODE BEGIN UsageFault_IRQn 0 */

  /* USER CODE END UsageFault_IRQn 0 */
  while (1)
  {
    /* USER CODE BEGIN W1_UsageFault_IRQn 0 */
    /* USER CODE END W1_UsageFault_IRQn 0 */
  }
}

/**
  * @brief This function handles System service call via SWI instruction.
  */
void SVC_Handler(void)
{
  /* USER CODE BEGIN SVCall_IRQn 0 */

  /* USER CODE END SVCall_IRQn 0 */
  /* USER CODE BEGIN SVCall_IRQn 1 */

  /* USER CODE END SVCall_IRQn 1 */
}

/**
  * @brief This function handles Debug monitor.
  */
void DebugMon_Handler(void)
{
  /* USER CODE BEGIN DebugMonitor_IRQn 0 */

  /* USER CODE END DebugMonitor_IRQn 0 */
  /* USER CODE BEGIN DebugMonitor_IRQn 1 */

  /* USER CODE END DebugMonitor_IRQn 1 */
}

/**
  * @brief This function handles Pendable request for system service.
  */
void PendSV_Handler(void)
{
  /* USER CODE BEGIN PendSV_IRQn 0 */

  /* USER CODE END PendSV_IRQn 0 */
  /* USER CODE BEGIN PendSV_IRQn 1 */

  /* USER CODE END PendSV_IRQn 1 */
}

/**
  * @brief This function handles System tick timer.
  */
void SysTick_Handler(void)
{
  /* USER CODE BEGIN SysTick_IRQn 0 */

  /* USER CODE END SysTick_IRQn 0 */
  HAL_IncTick();
  /* USER CODE BEGIN SysTick_IRQn 1 */

  /* USER CODE END SysTick_IRQn 1 */
}

/******************************************************************************/
/* STM32F1xx Peripheral Interrupt Handlers                                    */
/* Add here the Interrupt Handlers for the used peripherals.                  */
/* For the available peripheral interrupt handler names,                      */
/* please refer to the startup file (startup_stm32f1xx.s).                    */
/******************************************************************************/

/**
  * @brief This function handles EXTI line3 interrupt.
  */
void EXTI3_IRQHandler(void)
{
  /* USER CODE BEGIN EXTI3_IRQn 0 */

  /* USER CODE END EXTI3_IRQn 0 */
  HAL_GPIO_EXTI_IRQHandler(EXIT_KEY1_Pin);
  /* USER CODE BEGIN EXTI3_IRQn 1 */

  /* USER CODE END EXTI3_IRQn 1 */
}

/**
  * @brief This function handles EXTI line4 interrupt.
  */
void EXTI4_IRQHandler(void)
{
  /* USER CODE BEGIN EXTI4_IRQn 0 */

  /* USER CODE END EXTI4_IRQn 0 */
  HAL_GPIO_EXTI_IRQHandler(EXTI_KEY2_Pin);
  /* USER CODE BEGIN EXTI4_IRQn 1 */

  /* USER CODE END EXTI4_IRQn 1 */
}

/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

一、外部中断相关寄存器

PE3、PE4 的下降沿中断涉及四组硬件：

flowchart LR
    RCC[RCC<br/>开启 GPIOE/AFIO 时钟] --> GPIO[GPIOE<br/>输入上拉]
    GPIO --> AFIO[AFIO_EXTICR<br/>端口 E 映射到 EXTI3/4]
    AFIO --> EXTI[EXTI<br/>下降沿、屏蔽、挂起]
    EXTI --> NVIC[NVIC<br/>使能与优先级]
    NVIC --> CPU[CPU 进入向量函数]

只看 EXTI 寄存器还不够；EXTI 不负责选择“哪一个端口的 3 号脚”，这由 AFIO_EXTICR 完成，也不负责 CPU 级优先级，这由 NVIC 完成。

1.1 从代码层面对外部中断进行剖析

课程配置：

GPIO_InitStruct.Pin = EXIT_KEY1_Pin | EXTI_KEY2_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;
GPIO_InitStruct.Pull = GPIO_PULLUP;
HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);

GPIO_MODE_IT_FALLING 在 HAL 头文件中编码为 0x10210000。这个数不是直接写入某一个硬件寄存器，而是供 HAL_GPIO_Init 拆解：

0x10210000
│ ││
│ │└─ GPIO 输入配置
│ └── 中断模式
└──── 下降沿触发

HAL 对每一个选中的引脚依次配置 GPIO 四位字段、AFIO 映射、RTSR/FTSR、EMR/IMR。

1.1.1 GPIO的初始化

PE3 和 PE4 配为“上拉/下拉输入”：

GPIOE_CRL：
PE3 四位字段 CRL[15:12] = CNF3 MODE3 = 10 00
PE4 四位字段 CRL[19:16] = CNF4 MODE4 = 10 00

GPIOE_ODR：
ODR3 = 1  → 选择内部上拉
ODR4 = 1  → 选择内部上拉

STM32F1 的内部上拉和下拉共用 CNF=10；方向不是 CRL 中另一个位，而是由 ODR 对应位选择。HAL 在配置上拉时向 BSRR 写目标位，使 ODR 位变成 1；配置下拉时通过 BRR 清 ODR 位。

1.1.2 STM32的复位和时钟控制

RCC_APB2ENR 相关位：

位	名称	本实验
6	IOPEEN	置 1，开启 GPIOE
3	IOPBEN	置 1，开启 GPIOB
2	IOPAEN	工程也置 1
0	AFIOEN	HAL 配置 EXTI 时自动置 1

没有 AFIO 时钟，EXTICR 映射不能正确配置；没有 GPIOE 时钟，PE3/PE4 输入配置无效。

1.1.3 通用和复用功能I/O

AFIO_EXTICR1～4 每个寄存器管理四条 EXTI 线，每条线占 4 位：

寄存器	管理的线
EXTICR1	EXTI0～3
EXTICR2	EXTI4～7
EXTICR3	EXTI8～11
EXTICR4	EXTI12～15

端口编码：

编码	端口
0000	PA
0001	PB
0010	PC
0011	PD
0100	PE
0101	PF
0110	PG

所以本实验：

AFIO_EXTICR1[15:12] = EXTI3[3:0] = 0100  → PE3
AFIO_EXTICR2[ 3: 0] = EXTI4[3:0] = 0100  → PE4

字段计算公式：

寄存器下标 = line / 4
字段左移位 = (line % 4) × 4

HAL 源码中的 AFIO->EXTICR[position >> 2] 和 4 * (position & 3) 正是这两个运算。

1.1.4 外部中断/事件控制器

EXTI_TypeDef 只有六个 32 位寄存器：

typedef struct
{
    __IO uint32_t IMR;    /* 0x00 中断屏蔽 */
    __IO uint32_t EMR;    /* 0x04 事件屏蔽 */
    __IO uint32_t RTSR;   /* 0x08 上升沿选择 */
    __IO uint32_t FTSR;   /* 0x0C 下降沿选择 */
    __IO uint32_t SWIER;  /* 0x10 软件请求 */
    __IO uint32_t PR;     /* 0x14 挂起，写1清除 */
} EXTI_TypeDef;

位 0～18 分别对应 EXTI0～18；位 19 只在互联型器件上有效。普通 STM32F103 应把未实现位视为保留位。

寄存器位 x	写 0	写 1
IMR.MRx	屏蔽中断请求	开放中断请求
EMR.MRx	屏蔽事件请求	开放事件请求
RTSR.TRx	不检测上升沿	检测上升沿
FTSR.TRx	不检测下降沿	检测下降沿
SWIER.SWIEx	无请求	产生软件请求并置挂起
PR.PRx	无清除作用	清除该挂起位

PR 的“写 1 清除”最容易出错。正确做法是：

EXTI->PR = GPIO_PIN_3;  /* 清 PR3 */

不要用普通变量思维执行 EXTI->PR &= ~GPIO_PIN_3；这会先读到多个挂起位，再以不合适的方式写回，可能错误清除其他线路。

1.1.5 外部中断的初始化过程

以 PE3 为例，HAL_GPIO_Init 的过程可展开为：

1. GPIOE_CRL[15:12] = 0b1000       输入上拉/下拉
2. GPIOE_BSRR = 1 << 3              ODR3=1，选择上拉
3. RCC_APB2ENR.AFIOEN = 1           开 AFIO 时钟
4. AFIO_EXTICR1[15:12] = 0b0100    EXTI3 选择端口 E
5. EXTI_RTSR.TR3 = 0                关闭上升沿
6. EXTI_FTSR.TR3 = 1                打开下降沿
7. EXTI_EMR.MR3 = 0                 不走事件通路
8. EXTI_IMR.MR3 = 1                 打开中断通路

PE4 采用相同过程，目标位换成 4，映射字段位于 EXTICR2[3:0]。

1.1.5.1 GPIO速度定义

GPIO 速度宏只对输出模式有意义：

HAL 宏	STM32F1 MODE[1:0]	最大输出速度
GPIO_SPEED_FREQ_LOW	10	2 MHz
GPIO_SPEED_FREQ_MEDIUM	01	10 MHz
GPIO_SPEED_FREQ_HIGH	11	50 MHz

PE3/PE4 是输入模式，MODE 必须为 00，所以不使用 Speed 字段。把“输入中断速度”理解为 2/10/50 MHz 是不正确的；输入边沿能力由输入缓冲、EXTI 和数据手册电气特性决定。

1.1.6 外部中断的实现过程

按下 PE3 后：

sequenceDiagram
    participant P as PE3
    participant X as EXTI3
    participant N as NVIC
    participant H as EXTI3_IRQHandler
    participant C as Callback
    P->>X: 1→0
    X->>X: FTSR3=1，因此 PR3置1
    X->>N: IMR3=1，提交中断
    N->>H: IRQ已使能且优先级允许
    H->>X: HAL读取PR3
    H->>X: 向PR3写1清除
    H->>C: 参数GPIO_PIN_3

若边沿发生时 NVIC 通道关闭，EXTI 的 PR 位仍可能挂起；之后打开 NVIC，未清的请求可能立即得到服务。初始化结束前可按需要先清历史挂起位，再启用 NVIC。

1.1.7 PR寄存器

PR 是 Pending Register：

PRx=0：该线没有待处理请求
PRx=1：检测到所选边沿或软件请求
写 PRx=1：清除挂起

HAL 宏通常定义为：

#define __HAL_GPIO_EXTI_GET_IT(__PIN__)   (EXTI->PR & (__PIN__))
#define __HAL_GPIO_EXTI_CLEAR_IT(__PIN__) (EXTI->PR = (__PIN__))

清挂起应在确认请求后及时进行。如果先执行很长的业务逻辑再清除，期间的新边沿可能和旧状态混在一起；机械按键还会因抖动反复置位。

二、结束

PE3/PE4 下降沿中断的最终寄存器检查表：

检查项	PE3	PE4
GPIO 输入字段	CRL[15:12]=1000	CRL[19:16]=1000
上拉选择	ODR3=1	ODR4=1
AFIO 映射	EXTICR1[15:12]=0100	EXTICR2[3:0]=0100
上升沿	RTSR3=0	RTSR4=0
下降沿	FTSR3=1	FTSR4=1
中断开放	IMR3=1	IMR4=1
事件关闭	EMR3=0	EMR4=0
挂起清除	向 PR3 写 1	向 PR4 写 1

三、外部中断触发函数

EXTI3_IRQHandler 和 EXTI4_IRQHandler 是真正写入向量表的入口。它们只调用 HAL 分发函数，不直接读取按键或控制负载，这使底层清挂起与用户业务分离。

若使用 PE8，则对应 EXTI8，但 NVIC 入口是共享的 EXTI9_5_IRQHandler：

void EXTI9_5_IRQHandler(void)
{
    HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_8);
}

共享处理函数可能需要依次处理多个引脚，不能处理一个后直接忽略其他挂起位。

四、中断向量表

启动文件中的向量表保存处理函数地址。Cortex-M3 复位后通过向量表取得初始栈顶和 Reset_Handler；发生 EXTI3/EXTI4 中断时，NVIC 根据异常号索引对应入口。

向量表基址 VTOR
  + 0x00  初始 MSP
  + 0x04  Reset_Handler
  ...
  + 对应偏移  EXTI3_IRQHandler
  + 对应偏移  EXTI4_IRQHandler

函数名拼错、启动文件型号不匹配、目标文件未参与链接，都会导致弱默认处理函数被采用。此时外设寄存器可能已正确产生挂起，但程序进入默认死循环。因此寄存器、NVIC 状态和向量符号要一起检查。