STM32 掉電檢測程序

當VDD下降到PVD閥值以下或當VDD上升到PVD閥值之上時，根據外部中斷第16線的上升/下降邊沿觸發設置，就會產生PVD中斷

void  PVD_IRQHandler(void)
{
   led_ctrl(LED1, ON);

   if(PWR_GetFlagStatus(PWR_FLAG_PVDO))
   {
      MSD0_WriteSingleBlock(1, buf);
   }

   EXTI_ClearITPendingBit(EXTI_Line16);
}

void PVD_Init(void)
{
   EXTI_InitTypeDef EXTI_InitStructure;
   NVIC_InitTypeDef NVIC_InitStructure;

   NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
   NVIC_InitStructure.NVIC_IRQChannel = PVD_IRQn;
   NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
   NVIC_Init(&NVIC_InitStructure);

   RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);

   PWR_PVDLevelConfig(PWR_PVDLevel_2V9);	//可設置范圍：2.2-2.9V
   PWR_PVDCmd(ENABLE);

   EXTI_DeInit();
   EXTI_StructInit(&EXTI_InitStructure);
   EXTI_InitStructure.EXTI_Line = EXTI_Line16;	//PVD連接到外部中斷16
   EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
   EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
   EXTI_InitStructure.EXTI_LineCmd = ENABLE;
   EXTI_Init(&EXTI_InitStructure);
}

當檢測到掉電以后，led會亮一下，然后進行掉電保存操作。

注意：

1. 掉電時間有限，如果耗時較長的操作，可能會操作失敗；
2. 時鍾頻率設置也會有影響。（SysTick_Config）