（一）概述

stm32有两个看门狗：硬件看门狗（LSI 40KHz，时间精度不高）和窗口看门狗(APB1)。

（二）硬件看门狗实现代码

IWDG_HandleTypeDef hiwdg;// 硬件看门狗初始化
static void MX_IWDG_Init(IWDG_HandleTypeDef *pHiwdg)
{pHiwdg->Instance = IWDG;pHiwdg->Init.Prescaler = IWDG_PRESCALER_4;pHiwdg->Init.Reload = 0xFFF; // Tout = ((4 * 2^prer) * rlr) / 40 = 409ms，看门狗溢出时间if (HAL_IWDG_Init(pHiwdg) != HAL_OK){Error_Handler();}
}int main(void)
{........MX_IWDG_Init(&hiwdg);........HAL_IWDG_Start(&hiwdg);while (1){........HAL_IWDG_Refresh(&hiwdg);}}

（三）初始上电获取硬件看门狗复位状态

if (__HAL_RCC_GET_FLAG(RCC_FLAG_IWDGRST) != RESET)
{}/* 硬件看门狗复位 */__HAL_RCC_CLEAR_RESET_FLAGS();

（四）看门狗复位后IO状态的保持方法

法一：硬件方式，锁存器。

法二：软件方式，当需要关注的IO状态改变时，立马存在Flash中，初始上电判断复位类型是硬件看门狗，就进行Flash读取和IO操作。该方式的缺点：由于stm32的Flash写操作是页写，每次写之前，都要先擦除，而且Flash的写次数有限，故经常写，Flash经常写的区域有可能被写坏。

法三：软件方式，BKP+初始判断处理（stm32F103RC大容量，备份寄存器是42个16位的寄存器）。

// BKP
#define BKP_DATA_LEN               16   
#define BKP_MAX_DATA_LEN           42
#define BKP_INTERVAL_POINT         10// 写备份寄存器
void BKP_Write(uint8_t *pSourcedata, uint32_t num)
{assert_param(num <= BKP_MAX_DATA_LEN);volatile uint32_t *pDestData;RCC->APB1ENR |= (1 << 27 | 1 << 28); 	// 电源接口时钟/备份时钟开启PWR->CR |= 1 << 8;				 	// 允许写入后备寄存器if (num > BKP_INTERVAL_POINT){	pDestData = &(BKP->DR1);		for (uint32_t i = 0; i < BKP_INTERVAL_POINT; i++){*(pDestData + i) = *(pSourcedata + i);}pDestData = &(BKP->DR11);for (uint32_t i = 0; i < (num - BKP_INTERVAL_POINT); i++){*(pDestData + i) = *(pSourcedata + i + BKP_INTERVAL_POINT);}}else{pDestData = &(BKP->DR1);		for (uint32_t i = 0; i < num; i++){*(pDestData + i) = *(pSourcedata + i);}}	
}// 读备份寄存器
void BKP_Read(uint8_t *pReadData, uint32_t num)
{assert_param(num <= BKP_MAX_DATA_LEN);volatile uint32_t *pSourceData;	if (num > BKP_INTERVAL_POINT){pSourceData = &(BKP->DR1);for (uint32_t i = 0; i < BKP_INTERVAL_POINT; i++){*(pReadData + i) = *(pSourceData + i);}	pSourceData = &(BKP->DR11);for (uint32_t i = 0; i < (num - BKP_INTERVAL_POINT); i++){*(pReadData + i + BKP_INTERVAL_POINT) = *(pSourceData + i);}	}else{pSourceData = &(BKP->DR1);for (uint32_t i = 0; i < num; i++){*(pReadData + i) = *(pSourceData + i);}}
}