STM32的备份寄存器测试

1. 研究STM3的备份寄存器，注意，如果要测试这个例程的话，VBAT不能和VDD接一起，必须分开。

2. 理解，备份寄存器可以有VBAT独立供电，也就是外接电池，备份寄存器在VBAT供电情况下，如果发生系统复位（按键复位）和上电复位，备份寄存器的值可以保持。

3. 代码如下：

 int main(void)

 {

 #ifdef DEBUG

   debug();

 #endif

   /* System Clocks Configuration */

   RCC_Configuration();

   /* NVIC configuration */

   NVIC_Configuration();

   /* GPIO configuration */

   GPIO_Configuration();

   /* Enable PWR and BKP clock */

   RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);

   /* Enable write access to Backup domain */

   PWR_BackupAccessCmd(ENABLE);

   /* Clear Tamper pin Event(TE) pending flag */

   BKP_ClearFlag();

   //首先判断是不是上电复位的

   if(RCC_GetFlagStatus(RCC_FLAG_PORRST) != RESET)

   {

     /* Clear reset flags */

     RCC_ClearFlag();

     /* Turn on led connected to GPIO_LED Pin8 */

     GPIO_SetBits(GPIO_LED, GPIO_Pin_8);

     /* Check if Backup data registers are programmed */

     if(CheckBackupReg(0x3211) == 0x00)

     { /* Backup data registers values are correct */

       /* Turn on led connected to GPIO_LED Pin6 */

       GPIO_SetBits(GPIO_LED, GPIO_Pin_6);

     }

     else

     { /* Backup data registers values are not correct or they are not yet

          programmed (when the first time the program is executed) */

       /* Write data to Backup data registers */

       WriteToBackupReg(0x3211);

       /* Turn on led connected to GPIO_LED Pin7 */

       GPIO_SetBits(GPIO_LED, GPIO_Pin_7);

     }

   }

   /* Turn on led connected to GPIO_LED Pin9 */

   GPIO_SetBits(GPIO_LED, GPIO_Pin_9);

   while ()

   {

   }

 }

4. 测试，第一次上电，亮灯LED7，LED8，LED9，然后VDD断电重新上电，亮灯LED6，LED8，LED9，然后按复位按键，亮灯LED9（代码只检查是不是上电复位）