WWDG -窗口看门狗

本篇总结

配置 WWDG 窗口看门狗，演示中断喂狗防复位 + 不喂狗触发系统复位两种场景。

硬件平台：本例程基于 W55MH32L-EVB 开发板运行。

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超时时间公式

T_wwdg = T_PCLK1 × 4096 × 2^WDGTB × (T[5:0] + 1)
当 PCLK1 = 36MHz、WDGTB = 3（分频 8）时，计数器减一格约 910μs，最大超时约 58.3ms。

void UART_Configuration(uint32_t bound)
{
    GPIO_InitTypeDef  GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;

    /* 开启外设时钟 */
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    /* PA9: USART1_TX → 复用推挽输出 */
    GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    /* PA10: USART1_RX → 浮空输入 */
    GPIO_InitStructure.GPIO_Pin  = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    /* USART 参数：115200 / 8N1 / 全双工 */
    USART_InitStructure.USART_BaudRate            = bound;
    USART_InitStructure.USART_WordLength          = USART_WordLength_8b;
    USART_InitStructure.USART_StopBits            = USART_StopBits_1;
    USART_InitStructure.USART_Parity              = USART_Parity_No;
    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStructure.USART_Mode                = USART_Mode_Rx | USART_Mode_Tx;

    USART_Init(USART_TEST, &USART_InitStructure);
    USART_Cmd(USART_TEST, ENABLE);
}

void WWDG_Configuration(void)
{
    /* 开启 WWDG 时钟（挂载在 APB1） */
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_WWDG, ENABLE);

    /* 预分频器 8：CNT_CK = PCLK1 / 4096 / 8 */
    WWDG_SetPrescaler(WWDG_Prescaler_8);

    /* 窗口上限 0x5F：计数器在 0x40~0x5F 之间喂狗才合法 */
    WWDG_SetWindowValue(0x5F);

    /* 使能 WWDG，初始计数器值 0x7F（最大值，T6 必须为 1） */
    WWDG_Enable(0x7F);
}

如果你想自定义

• 改超时时间 → 修改 WWDG_SetPrescaler 参数为 WWDG_Prescaler_1/2/4/8，分频越大超时越长
• 改窗口范围 → 修改 WWDG_SetWindowValue 参数（0x41~0x7F），值越小窗口越宽，喂狗时机越宽松

/* NVIC 中断优先级配置 */
void NVIC_Configuration(void)
{
    NVIC_InitTypeDef NVIC_InitStructure;
    NVIC_InitStructure.NVIC_IRQChannel                   = WWDG_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority        = 3;
    NVIC_InitStructure.NVIC_IRQChannelCmd                = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
}

/* WWDG 提前唤醒中断（EWI）：计数器减到 0x40 时触发，此处喂狗防复位 */
void WWDG_IRQHandler(void)
{
    WWDG_SetCounter(0x7F);   /* 喂狗：重装计数器到最大值 */
    WWDG_ClearFlag();        /* 清除中断标志，等待下一次触发 */
}

中断喂狗的代价

中断喂狗虽能防复位，但若程序主循环跑飞、只剩中断在喂，看门狗就失去了监控意义。生产环境中应在中断里加上"看主循环是否正常运行"的判断，而非无条件喂狗。

int main(void)
{
    RCC_ClocksTypeDef clocks;

    delay_init();
    UART_Configuration(115200);
    RCC_GetClocksFreq(&clocks);

    printf("\n");
    printf("SYSCLK: %3.1fMhz, HCLK: %3.1fMhz, PCLK1: %3.1fMhz, "
           "PCLK2: %3.1fMhz, ADCCLK: %3.1fMhz\n",
           (float)clocks.SYSCLK_Frequency / 1000000,
           (float)clocks.HCLK_Frequency / 1000000,
           (float)clocks.PCLK1_Frequency / 1000000,
           (float)clocks.PCLK2_Frequency / 1000000,
           (float)clocks.ADCCLK_Frequency / 1000000);
    printf("WWDG Int Test.\n");
    printf("Interrupt Feed Dog\n");

    /* 配置 WWDG：预分频 8 / 窗口 0x5F / 计数器 0x7F */
    WWDG_Configuration();

    /* 使能提前唤醒中断 */
    WWDG_ClearFlag();
    NVIC_Configuration();
    WWDG_EnableIT();

    while (1);   /* 主循环空转，由 EWI 中断自动喂狗 */
}

int main(void)
{
    RCC_ClocksTypeDef clocks;

    delay_init();
    UART_Configuration(115200);
    RCC_GetClocksFreq(&clocks);

    printf("\n");
    printf("SYSCLK: %3.1fMhz, HCLK: %3.1fMhz, PCLK1: %3.1fMhz, "
           "PCLK2: %3.1fMhz, ADCCLK: %3.1fMhz\n",
           (float)clocks.SYSCLK_Frequency / 1000000,
           (float)clocks.HCLK_Frequency / 1000000,
           (float)clocks.PCLK1_Frequency / 1000000,
           (float)clocks.PCLK2_Frequency / 1000000,
           (float)clocks.ADCCLK_Frequency / 1000000);
    printf("WWDG Reset Test.\n");

    /* 配置 WWDG：预分频 8 / 窗口 0x5F / 计数器 0x7F */
    WWDG_Configuration();

    /* 不使能中断、不喂狗 → 计数器减到 0x40 触发系统复位 */
    while (1);
}

调试小技巧

若想在 WWDG_IRQHandler 中确认喂狗是否执行，可加一行 printf("[WWDG] Feed dog!\n");，串口会周期性打印该信息。

int fputc(int c, FILE *f)
{
    if (c == '\n')
        SER_PutChar('\r');         // 补回车，确保串口工具正确换行
    return (SER_PutChar(c));
}

int SER_PutChar(int ch)
{
    while (!USART_GetFlagStatus(USART_TEST, USART_FLAG_TC));
    USART_SendData(USART_TEST, (uint8_t)ch);
    return ch;
}