STM32F0xx_StdPeriph_Examples/RTC/RTC_LSI/main.c

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/**
  ******************************************************************************
  * @file    RTC/RTC_LSI/main.c 
  * @author  MCD Application Team
  * @version V1.4.0
  * @date    24-July-2014
  * @brief   Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; COPYRIGHT 2014 STMicroelectronics</center></h2>
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
  */

/* Includes ------------------------------------------------------------------*/
#include "main.h"

/** @addtogroup STM32F0xx_StdPeriph_Examples
  * @{
  */

/** @addtogroup RTC_LSI
  * @{
  */

/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
RTC_InitTypeDef   RTC_InitStructure;
__IO uint32_t LsiFreq = 0;
__IO uint32_t CaptureNumber = 0, PeriodValue = 0;

/* Private function prototypes -----------------------------------------------*/
static void RTC_Config(void);
static uint32_t GetLSIFrequency(void);

/* Private functions ---------------------------------------------------------*/

/**
  * @brief  Main program.
  * @param  None
  * @retval None
  */
int main(void)
{
  /*!< At this stage the microcontroller clock setting is already configured, 
       this is done through SystemInit() function which is called from startup
       file (startup_stm32f0xx.s) before to branch to application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f0xx.c file
     */ 

/* Initialize LEDs mounted on STM320518-EVAL board --------------------------*/
  STM_EVAL_LEDInit(LED1);
  STM_EVAL_LEDInit(LED2);
  STM_EVAL_PBInit(BUTTON_TAMPER, BUTTON_MODE_GPIO);
  
  /* RTC Configuration -------------------------------------------------------*/
  RTC_Config();

  /* Wait Until KEY BUTTON is pressed */
  while(STM_EVAL_PBGetState(BUTTON_TAMPER) != RESET)
  {
  }
  
  /* Get the LSI frequency:  TIM14 is used to measure the LSI frequency */
  LsiFreq = GetLSIFrequency();

  /* Turn on LED2 */
  STM_EVAL_LEDOn(LED2);
  
  /* Calendar Configuration */
  RTC_InitStructure.RTC_AsynchPrediv = 99;
  RTC_InitStructure.RTC_SynchPrediv     =  (LsiFreq/100) - 1;
  RTC_InitStructure.RTC_HourFormat = RTC_HourFormat_24;
  RTC_Init(&RTC_InitStructure);

  /* Infinite loop */
  while (1)
  {
  }
}

/**
  * @brief  Configure the RTC peripheral by selecting the clock source.
  * @param  None
  * @retval None
  */
static void RTC_Config(void)
{
  RTC_TimeTypeDef RTC_TimeStructure;
  NVIC_InitTypeDef NVIC_InitStructure; 
  EXTI_InitTypeDef EXTI_InitStructure;
  RTC_AlarmTypeDef RTC_AlarmStructure;
  /* Enable the PWR clock */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);
  
  /* Allow access to RTC */
  PWR_BackupAccessCmd(ENABLE);

/* LSI used as RTC source clock */
/* The RTC Clock may varies due to LSI frequency dispersion. */   
  /* 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 the RTC Clock */
  RCC_RTCCLKCmd(ENABLE);

  /* Wait for RTC APB registers synchronisation */
  RTC_WaitForSynchro();

  /* Calendar Configuration */
  RTC_InitStructure.RTC_AsynchPrediv = 99;
  RTC_InitStructure.RTC_SynchPrediv     =  399; /* (40KHz / 100) - 1 = 399*/
  RTC_InitStructure.RTC_HourFormat = RTC_HourFormat_24;
  RTC_Init(&RTC_InitStructure);  

  /* EXTI configuration *******************************************************/
  EXTI_ClearITPendingBit(EXTI_Line17);
  EXTI_InitStructure.EXTI_Line = EXTI_Line17;
  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;
  EXTI_Init(&EXTI_InitStructure);
  
  /* Enable the RTC Wakeup Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = RTC_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
  
    /* Set the alarm X+5s */
  RTC_AlarmStructure.RTC_AlarmTime.RTC_H12     = RTC_H12_AM;
  RTC_AlarmStructure.RTC_AlarmTime.RTC_Hours   = 0x00;
  RTC_AlarmStructure.RTC_AlarmTime.RTC_Minutes = 0x00;
  RTC_AlarmStructure.RTC_AlarmTime.RTC_Seconds = 0x01;
  RTC_AlarmStructure.RTC_AlarmDateWeekDay = 0x31;
  RTC_AlarmStructure.RTC_AlarmDateWeekDaySel = RTC_AlarmDateWeekDaySel_Date;
  RTC_AlarmStructure.RTC_AlarmMask = RTC_AlarmMask_DateWeekDay;
  RTC_SetAlarm(RTC_Format_BCD, RTC_Alarm_A, &RTC_AlarmStructure);

  RTC_ITConfig(RTC_IT_ALRA, ENABLE);
    
  /* Enable the alarm */
  RTC_AlarmCmd(RTC_Alarm_A, ENABLE);
  
  /* Set the time to 00h 00mn 00s AM */
  RTC_TimeStructure.RTC_H12     = RTC_H12_AM;
  RTC_TimeStructure.RTC_Hours   = 0x00;
  RTC_TimeStructure.RTC_Minutes = 0x00;
  RTC_TimeStructure.RTC_Seconds = 0x00;  
  
  RTC_SetTime(RTC_Format_BCD, &RTC_TimeStructure);
}

/**
  * @brief  Configures TIM14 to measure the LSI oscillator frequency. 
  * @param  None
  * @retval LSI Frequency
  */
static uint32_t GetLSIFrequency(void)
{
  NVIC_InitTypeDef   NVIC_InitStructure;
  TIM_ICInitTypeDef  TIM_ICInitStructure;
  RCC_ClocksTypeDef  RCC_ClockFreq;

  /* TIM14 configuration *******************************************************/ 
  /* Enable TIM14 clock */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM14, ENABLE);
  
  /* Reset TIM14 registers */
  TIM_DeInit(TIM14);

  /* Configure TIM14 prescaler */
  TIM_PrescalerConfig(TIM14, 0, TIM_PSCReloadMode_Immediate);

  /* Connect internally the TIM14_CH1 to the RTC clock output */
  TIM_RemapConfig(TIM14, TIM14_RTC_CLK);

  /* TIM14 configuration: Input Capture mode ---------------------
     The reference clock(LSE or external) is connected to TIM14 CH1
     The Rising edge is used as active edge,
     The TIM14 CCR1 is used to compute the frequency value 
  ------------------------------------------------------------ */
  TIM_ICInitStructure.TIM_Channel     = TIM_Channel_1;
  TIM_ICInitStructure.TIM_ICPolarity  = TIM_ICPolarity_Rising;
  TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV8;
  TIM_ICInitStructure.TIM_ICFilter = 0x0;
  TIM_ICInit(TIM14, &TIM_ICInitStructure);

  /* Enable the TIM14 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM14_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

  /* Enable TIM14 counter */
  TIM_Cmd(TIM14, ENABLE);

  /* Reset the flags */
  TIM14->SR = 0;
    
  /* Enable the CC1 Interrupt Request */  
  TIM_ITConfig(TIM14, TIM_IT_CC1, ENABLE);


  /* Wait until the TIM14 get 2 LSI edges (refer to TIM14_IRQHandler() in 
    stm32F0xx_it.c file) ******************************************************/
  while(CaptureNumber != 2)
  {
  }
  /* Deinitialize the TIM14 peripheral registers to their default reset values */
  TIM_DeInit(TIM14);


  /* Compute the LSI frequency, depending on TIM14 input clock frequency (PCLK1)*/
  /* Get SYSCLK, HCLK and PCLKx frequency */
  RCC_GetClocksFreq(&RCC_ClockFreq);
  
  /* PCLK1 prescaler equal to 1 => TIMCLK = PCLK1 */
  return ((RCC_ClockFreq.PCLK_Frequency / PeriodValue) * 8);
}

#ifdef  USE_FULL_ASSERT

/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t* file, uint32_t line)
{ 
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

  /* Infinite loop */
  while (1)
  {
  }
}
#endif

/**
  * @}
  */

/**
  * @}
  */

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/