stm32f4xx_rtc.c

STM3240G-Eval_uCOS-III

  1. The RTC Prescaler is programmed to generate the RTC 1Hz time base. It is
     split into 2 programmable prescalers to minimize power consumption.
     - A 7-bit asynchronous prescaler and A 13-bit synchronous prescaler.
     - When both prescalers are used, it is recommended to configure the asynchronous
       prescaler to a high value to minimize consumption.

  2. All RTC registers are Write protected. Writing to the RTC registers
     is enabled by writing a key into the Write Protection register, RTC_WPR.

  3. To Configure the RTC Calendar, user application should enter initialization
     mode. In this mode, the calendar counter is stopped and its value can be 
     updated. When the initialization sequence is complete, the calendar restarts 
     counting after 4 RTCCLK cycles.

  4. To read the calendar through the shadow registers after Calendar initialization,
     calendar update or after wakeup from low power modes the software must first 
     clear the RSF flag. The software must then wait until it is set again before 
     reading the calendar, which means that the calendar registers have been 
     correctly copied into the RTC_TR and RTC_DR shadow registers.
     The RTC_WaitForSynchro() function implements the above software sequence 
     (RSF clear and RSF check).

@endverbatim
  * @{
  */

/**
  * @brief  Deinitializes the RTC registers to their default reset values.
  * @note   This function doesn't reset the RTC Clock source and RTC Backup Data
  *         registers.       
  * @param  None
  * @retval An ErrorStatus enumeration value:
  *          - SUCCESS: RTC registers are deinitialized
  *          - ERROR: RTC registers are not deinitialized
  */
ErrorStatus RTC_DeInit(void)
{
  __IO uint32_t wutcounter = 0x00;
  uint32_t wutwfstatus = 0x00;
  ErrorStatus status = ERROR;
  
  /* Disable the write protection for RTC registers */
  RTC->WPR = 0xCA;
  RTC->WPR = 0x53;

  /* Set Initialization mode */
  if (RTC_EnterInitMode() == ERROR)
  {
    status = ERROR;
  }  
  else
  {
    /* Reset TR, DR and CR registers */
    RTC->TR = (uint32_t)0x00000000;
    RTC->DR = (uint32_t)0x00002101;
    /* Reset All CR bits except CR[2:0] */
    RTC->CR &= (uint32_t)0x00000007;
  
    /* Wait till RTC WUTWF flag is set and if Time out is reached exit */
    do
    {
      wutwfstatus = RTC->ISR & RTC_ISR_WUTWF;
      wutcounter++;  
    } while((wutcounter != INITMODE_TIMEOUT) && (wutwfstatus == 0x00));
    
    if ((RTC->ISR & RTC_ISR_WUTWF) == RESET)
    {
      status = ERROR;
    }
    else
    {
      /* Reset all RTC CR register bits */
      RTC->CR &= (uint32_t)0x00000000;
      RTC->WUTR = (uint32_t)0x0000FFFF;
      RTC->PRER = (uint32_t)0x007F00FF;
      RTC->CALIBR = (uint32_t)0x00000000;
      RTC->ALRMAR = (uint32_t)0x00000000;        
      RTC->ALRMBR = (uint32_t)0x00000000;
      
      /* Reset ISR register and exit initialization mode */
      RTC->ISR = (uint32_t)0x00000000;
      
      /* Reset Tamper and alternate functions configuration register */
      RTC->TAFCR = 0x00000000;
  
      if(RTC_WaitForSynchro() == ERROR)
      {
        status = ERROR;
      }
      else
      {
        status = SUCCESS;      
      }
    }
  }
  
  /* Enable the write protection for RTC registers */
  RTC->WPR = 0xFF;  
  
  return status;
}

/**
  * @brief  Initializes the RTC registers according to the specified parameters 
  *         in RTC_InitStruct.
  * @param  RTC_InitStruct: pointer to a RTC_InitTypeDef structure that contains 
  *         the configuration information for the RTC peripheral.
  * @note   The RTC Prescaler register is write protected and can be written in 
  *         initialization mode only.  
  * @retval An ErrorStatus enumeration value:
  *          - SUCCESS: RTC registers are initialized
  *          - ERROR: RTC registers are not initialized  
  */
ErrorStatus RTC_Init(RTC_InitTypeDef* RTC_InitStruct)
{
  ErrorStatus status = ERROR;
  
  /* Check the parameters */
  assert_param(IS_RTC_HOUR_FORMAT(RTC_InitStruct->RTC_HourFormat));
  assert_param(IS_RTC_ASYNCH_PREDIV(RTC_InitStruct->RTC_AsynchPrediv));
  assert_param(IS_RTC_SYNCH_PREDIV(RTC_InitStruct->RTC_SynchPrediv));

  /* Disable the write protection for RTC registers */
  RTC->WPR = 0xCA;
  RTC->WPR = 0x53;

  /* Set Initialization mode */
  if (RTC_EnterInitMode() == ERROR)
  {
    status = ERROR;
  } 
  else
  {
    /* Clear RTC CR FMT Bit */
    RTC->CR &= ((uint32_t)~(RTC_CR_FMT));
    /* Set RTC_CR register */
    RTC->CR |=  ((uint32_t)(RTC_InitStruct->RTC_HourFormat));
  
    /* Configure the RTC PRER */
    RTC->PRER = (uint32_t)(RTC_InitStruct->RTC_SynchPrediv);
    RTC->PRER |= (uint32_t)(RTC_InitStruct->RTC_AsynchPrediv << 16);

    /* Exit Initialization mode */
    RTC_ExitInitMode();

    status = SUCCESS;    
  }
  /* Enable the write protection for RTC registers */
  RTC->WPR = 0xFF; 
  
  return status;
}

/**
  * @brief  Fills each RTC_InitStruct member with its default value.
  * @param  RTC_InitStruct: pointer to a RTC_InitTypeDef structure which will be 
  *         initialized.
  * @retval None
  */
void RTC_StructInit(RTC_InitTypeDef* RTC_InitStruct)
{
  /* Initialize the RTC_HourFormat member */
  RTC_InitStruct->RTC_HourFormat = RTC_HourFormat_24;
    
  /* Initialize the RTC_AsynchPrediv member */
  RTC_InitStruct->RTC_AsynchPrediv = (uint32_t)0x7F;

  /* Initialize the RTC_SynchPrediv member */
  RTC_InitStruct->RTC_SynchPrediv = (uint32_t)0xFF; 
}

/**
  * @brief  Enables or disables the RTC registers write protection.
  * @note   All the RTC registers are write protected except for RTC_ISR[13:8], 
  *         RTC_TAFCR and RTC_BKPxR.
  * @note   Writing a wrong key reactivates the write protection.
  * @note   The protection mechanism is not affected by system reset.  
  * @param  NewState: new state of the write protection.
  *          This parameter can be: ENABLE or DISABLE.
  * @retval None
  */
void RTC_WriteProtectionCmd(FunctionalState NewState)
{
  /* Check the parameters */
  assert_param(IS_FUNCTIONAL_STATE(NewState));
    
  if (NewState != DISABLE)
  {
    /* Enable the write protection for RTC registers */
    RTC->WPR = 0xFF;   
  }
  else
  {
    /* Disable the write protection for RTC registers */
    RTC->WPR = 0xCA;
    RTC->WPR = 0x53;    
  }
}

/**
  * @brief  Enters the RTC Initialization mode.
  * @note   The RTC Initialization mode is write protected, use the 
  *         RTC_WriteProtectionCmd(DISABLE) before calling this function.    
  * @param  None
  * @retval An ErrorStatus enumeration value:
  *          - SUCCESS: RTC is in Init mode
  *          - ERROR: RTC is not in Init mode  
  */
ErrorStatus RTC_EnterInitMode(void)
{
  __IO uint32_t initcounter = 0x00;
  ErrorStatus status = ERROR;
  uint32_t initstatus = 0x00;
     
  /* Check if the Initialization mode is set */
  if ((RTC->ISR & RTC_ISR_INITF) == (uint32_t)RESET)
  {
    /* Set the Initialization mode */
    RTC->ISR = (uint32_t)RTC_INIT_MASK;
    
    /* Wait till RTC is in INIT state and if Time out is reached exit */
    do
    {
      initstatus = RTC->ISR & RTC_ISR_INITF;
      initcounter++;  
    } while((initcounter != INITMODE_TIMEOUT) && (initstatus == 0x00));
    
    if ((RTC->ISR & RTC_ISR_INITF) != RESET)
    {
      status = SUCCESS;
    }
    else
    {
      status = ERROR;
    }        
  }
  else
  {
    status = SUCCESS;  
  } 
    
  return (status);  
}

/**
  * @brief  Exits the RTC Initialization mode.
  * @note   When the initialization sequence is complete, the calendar restarts 
  *         counting after 4 RTCCLK cycles.  
  * @note   The RTC Initialization mode is write protected, use the 
  *         RTC_WriteProtectionCmd(DISABLE) before calling this function.      
  * @param  None
  * @retval None
  */
void RTC_ExitInitMode(void)
{ 
  /* Exit Initialization mode */
  RTC->ISR &= (uint32_t)~RTC_ISR_INIT;  
}

/**
  * @brief  Waits until the RTC Time and Date registers (RTC_TR and RTC_DR) are 
  *         synchronized with RTC APB clock.
  * @note   The RTC Resynchronization mode is write protected, use the 
  *         RTC_WriteProtectionCmd(DISABLE) before calling this function. 
  * @note   To read the calendar through the shadow registers after Calendar 
  *         initialization, calendar update or after wakeup from low power modes 
  *         the software must first clear the RSF flag. 
  *         The software must then wait until it is set again before reading 
  *         the calendar, which means that the calendar registers have been 
  *         correctly copied into the RTC_TR and RTC_DR shadow registers.   
  * @param  None
  * @retval An ErrorStatus enumeration value:
  *          - SUCCESS: RTC registers are synchronised
  *          - ERROR: RTC registers are not synchronised
  */
ErrorStatus RTC_WaitForSynchro(void)
{
  __IO uint32_t synchrocounter = 0;
  ErrorStatus status = ERROR;
  uint32_t synchrostatus = 0x00;

  /* Disable the write protection for RTC registers */
  RTC->WPR = 0xCA;
  RTC->WPR = 0x53;
    
  /* Clear RSF flag */
  RTC->ISR &= (uint32_t)RTC_RSF_MASK;
    
  /* Wait the registers to be synchronised */
  do
  {
    synchrostatus = RTC->ISR & RTC_ISR_RSF;
    synchrocounter++;  
  } while((synchrocounter != SYNCHRO_TIMEOUT) && (synchrostatus == 0x00));
    
  if ((RTC->ISR & RTC_ISR_RSF) != RESET)
  {
    status = SUCCESS;
  }
  else
  {
    status = ERROR;
  }        

  /* Enable the write protection for RTC registers */
  RTC->WPR = 0xFF; 
    
  return (status); 
}

/**
  * @brief  Enables or disables the RTC reference clock detection.
  * @param  NewState: new state of the RTC reference clock.
  *          This parameter can be: ENABLE or DISABLE.
  * @retval An ErrorStatus enumeration value:
  *          - SUCCESS: RTC reference clock detection is enabled
  *          - ERROR: RTC reference clock detection is disabled  
  */
ErrorStatus RTC_RefClockCmd(FunctionalState NewState)
{ 
  ErrorStatus status = ERROR;
  
  /* Check the parameters */
  assert_param(IS_FUNCTIONAL_STATE(NewState));
  
  /* Disable the write protection for RTC registers */
  RTC->WPR = 0xCA;
  RTC->WPR = 0x53;
    
  /* Set Initialization mode */
  if (RTC_EnterInitMode() == ERROR)