关于RTC晶体起振条件

gujingyangguang 2009-3-11 10:54 楼主

前面在DEBUG过程中一直认为是晶体问题，要求6P，结果试了很多个6P晶体均无法起振，反复很长时间，也按照要求去选择晶体，直到后来看了下参考DEMO的电路图，发现PC13引脚被上拉了，后来参照接法，就很快起振了(本人电路为下拉)，但之前察看了很多个参考资料均未提及此条件，不知为何，还请斑竹确认下。
另在初始化时将侵入检测重新关闭一次，也可以起振，这点也未看到有提示，还请核实，是否如此。THKS！！！

回复评论（18）

沙发 chenyu19845

程序里怎么处理的？

点赞 2009-3-11 11:07

板凳崔明义

playzwm，你的RTC的时钟初始化有问题

你的问题与PC13引脚被上拉无关。

点赞 2009-3-11 11:42

4楼 amanonline

RTC初始化程序

相关初始化程序为：
/*******************************************************************************
* Function Name  : main
* Description    : Main program
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
int main(void)
{
int len;
u8 bufs[50];
#ifdef DEBUG
debug();
#endif

/* System Clocks Configuration */
RCC_Configuration();

/* NVIC configuration */
NVIC_Configuration();

  /* SysTick end of count event each 1ms with input clock equal to 9MHz (HCLK/8, default) */

TIM_Configuration();
GPIO_Configuration();

if (BKP_ReadBackupRegister(BKP_DR1) != 0x5AA5)
   {
     /* Backup data register value is not correct or not yet programmed (when
        the first time the program is executed) */

     //printf(" RTC not yet configured....");

     /* RTC Configuration */
  if(RTC_LSE_Configuration())
#if 1
  {
   LedAlarm(HIGH_LEVEL);
   while(1);
  }
  else
  {
   LedFail(LOW_LEVEL);
   LedAlarm(LOW_LEVEL);
   LedRun(HIGH_LEVEL);
  }
#else
       RTC_Configuration();
#endif

     /* Adjust time by values entred by the user on the hyperterminal */
     Time_Adjust(secondcount);

     BKP_WriteBackupRegister(BKP_DR1, 0x5AA5);
   }
   else
   {
     /* Check if the Power On Reset flag is set */
     if (RCC_GetFlagStatus(RCC_FLAG_PORRST) != RESET)
     {
       //printf(" Power On Reset occurred....");
     }
     /* Check if the Pin Reset flag is set */
     else if (RCC_GetFlagStatus(RCC_FLAG_PINRST) != RESET)
     {
       //printf(" External Reset occurred....");
     }

     //printf(" No need to configure RTC....");
     /* Wait for RTC registers synchronization */
     RTC_WaitForSynchro();

     /* Enable the RTC Second */
     RTC_ITConfig(RTC_IT_SEC, ENABLE);
     /* Wait until last write operation on RTC registers has finished */
     RTC_WaitForLastTask();
   }

LcdInit();
InitKey();

/* Initialize the SPI FLASH driver */
SPI_FLASH_Init();

ADCInit();
SPI_ADC_Init();

DisplayMenuTest();

while (1)
{
len=ReadComm(1, bufs, 8);

if(len)//<100*1024)
{ //int i;
  //for(i = 0; i < 0x2000; i++);
  WriteComm(1, bufs, len);

  //len+=len;
}
}
}

/*******************************************************************************
* Function Name  : RCC_Configuration
* Description    : Configures the different system clocks.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
void RCC_Configuration(void)
{
  /* RCC system reset(for debug purpose) */
  RCC_DeInit();

  /* Enable HSE */
  RCC_HSEConfig(RCC_HSE_ON);

  /* Wait till HSE is ready */
  HSEStartUpStatus = RCC_WaitForHSEStartUp();

  if(HSEStartUpStatus == SUCCESS)
  {
    /* Enable Prefetch Buffer */
    FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);

    /* Flash 2 wait state */
    FLASH_SetLatency(FLASH_Latency_2);

    /* HCLK = SYSCLK */
    RCC_HCLKConfig(RCC_SYSCLK_Div1);

    /* PCLK2 = HCLK */
    RCC_PCLK2Config(RCC_HCLK_Div1);

    /* PCLK1 = HCLK/2 */
    RCC_PCLK1Config(RCC_HCLK_Div2);

    /* ADCCLK = PCLK2/4 */
    RCC_ADCCLKConfig(RCC_PCLK2_Div4);
    /* PLLCLK = 8MHz * 9 = 72 MHz */
    RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);

    /* Enable PLL */
    RCC_PLLCmd(ENABLE);

    /* Wait till PLL is ready */
    while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
    {
    }

    /* Select PLL as system clock source */
    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

    /* Wait till PLL is used as system clock source */
    while(RCC_GetSYSCLKSource() != 0x08)
    {
    }
  }


/* Enable peripheral clocks --------------------------------------------------*/
  /* Enable DMA1 clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
  /* Enable GPIOA and USART1 clocks */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ALL , ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2|RCC_APB1Periph_TIM3|RCC_APB1Periph_SPI2|RCC_APB1Periph_TIM2|RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);
}

#endif
/*******************************************************************************
* Function Name  : NVIC_Configuration
* Description    : Configures the nested vectored interrupt controller.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
void NVIC_Configuration(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;

#ifdef  VECT_TAB_RAM
  /* Set the Vector Table base location at 0x20000000 */
  NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0);
#else  /* VECT_TAB_FLASH  */
  /* Set the Vector Table base location at 0x08000000 */
#ifdef  VECT_DFU
  NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x4000);
#else
  NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
#endif
#endif

  /* Configure one bit for preemption priority */
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);

  /* Enable the RTC Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = RTC_IRQChannel;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
  /* Enable the USART1 Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQChannel;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

    /* Enable the DMA1 Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel1_IRQChannel;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

    /* Enable the TIM2 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQChannel;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

/*******************************************************************************
* Function Name  : RTC_Configuration
* Description    : Configures the RTC.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/

void RTC_Configuration(void)
{
  /* Enable PWR and BKP clocks */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);

  /* Allow access to BKP Domain */
  PWR_BackupAccessCmd(ENABLE);

  /* Reset Backup Domain */
  BKP_DeInit();

  /* Enable the LSI OSC */
  RCC_LSICmd(ENABLE);
  /* Wait till LSI is ready */
  while (RCC_GetFlagStatus(RCC_FLAG_LSIRDY) == RESET)
  {}
  /* Select the RTC Clock Source */
  RCC_RTCCLKConfig(RCC_RTCCLKSource_LSI);

  /* Enable RTC Clock */
  RCC_RTCCLKCmd(ENABLE);

  /* Wait for RTC registers synchronization */
  RTC_WaitForSynchro();

  /* Wait until last write operation on RTC registers has finished */
  RTC_WaitForLastTask();

  /* Enable the RTC Second */
  RTC_ITConfig(RTC_IT_SEC, ENABLE);

  /* Wait until last write operation on RTC registers has finished */
  RTC_WaitForLastTask();

  /* Set RTC prescaler: set RTC period to 1sec */
  RTC_SetPrescaler(40000);

  /* Wait until last write operation on RTC registers has finished */
  RTC_WaitForLastTask();

  /* To output second signal on Tamper pin, the tamper functionality
       must be disabled (by default this functionality is disabled) */
  BKP_TamperPinCmd(DISABLE);

  /* Enable the RTC Second Output on Tamper Pin */
  BKP_RTCOutputConfig(BKP_RTCOutputSource_Second);
}

int RTC_LSE_Configuration(void)
{
u32 tick1,tick2;

  /* Enable PWR and BKP clocks */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);

  /* Allow access to BKP Domain */
  PWR_BackupAccessCmd(ENABLE);

  /* Reset Backup Domain */
  BKP_DeInit();

  /* Enable LSE */
  RCC_LSEConfig(RCC_LSE_ON);
  /* Wait till LSE is ready */
  tick1 = 0;
  while (RCC_GetFlagStatus(RCC_FLAG_LSERDY) == RESET)
  {
   LedFail(HIGH_LEVEL);
   Delayms(3000);
LedFail(LOW_LEVEL);
   Delayms(3000);
RCC_LSEConfig(RCC_LSE_ON);
  }
if(RCC_GetFlagStatus(RCC_FLAG_LSERDY) == RESET)
{
  xtal_32k = 1;
  //RCC_LSEConfig(RCC_LSE_OFF);
  //PrintStr(10, 10, "LSE work abnormal", 16);
  //Delayms(2000);
  return 1;
}

  /* Select LSE as RTC Clock Source */
  RCC_RTCCLKConfig(RCC_RTCCLKSource_LSE);

  /* Enable RTC Clock */
  RCC_RTCCLKCmd(ENABLE);

  /* Wait for RTC registers synchronization */
  RTC_WaitForSynchro();

  /* Wait until last write operation on RTC registers has finished */
  RTC_WaitForLastTask();

  /* Enable the RTC Second */
  RTC_ITConfig(RTC_IT_SEC, ENABLE);

  /* Wait until last write operation on RTC registers has finished */
  RTC_WaitForLastTask();

  /* Set RTC prescaler: set RTC period to 1sec */
  RTC_SetPrescaler(32767); /* RTC period = RTCCLK/RTC_PR = (32.768 KHz)/(32767+1) */

  /* Wait until last write operation on RTC registers has finished */
  RTC_WaitForLastTask();

  return 0;
}

点赞 2009-3-11 11:52