/**
  @page RTC_LSI RTC prescaler adjustment with LSI Measurements example
  
  @verbatim
  ******************** (C) COPYRIGHT 2015 STMicroelectronics *******************
  * @file    RTC/RTC_LSI/readme.txt 
  * @author  MCD Application Team
  * @version V1.1.3
  * @date    15-December-2021
  * @brief   Description of the RTC prescaler adjustment with LSI Measurements example.
  ******************************************************************************
  *
  * Copyright (c) 2015 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
   @endverbatim

@par Example Description 

This example demonstrates and explains how to use the LSI clock source auto
calibration to get a precise RTC clock. 
As an application example, it demonstrates how to configure the TIM16 timer
internally connected to LSI clock output, in order to adjust the RTC prescaler. 

The Low Speed Internal (LSI) clock is used as RTC clock source.
After reset, the RTC prescaler (asynchronous and synchronous) is set with the 
default LSI frequency (42KHz).
The RTC wakeup is configured to generate an interrupt each 1s. LED1 is toggled 
inside the RTC WakeUp interrupt each 1s.

The inaccuracy of the LSI clock causes the RTC wakeup Interrupt to be inaccurate.
The RTC CK_SPRE signal can be monitored by LED1 which is toggled into the RTC 
wakeup interrupt service routine.

The program waits until Key Push button is pressed to begin the auto calibration 
procedure:
 - Configure the TIM16 to remap internally the TIM16 Channel 1 Input Capture to 
   the LSI clock output.
 - Enable the TIM16 Input Capture interrupt: after one cycle of LSI clock, the
   period value is stored in a variable and compared to the HCLK clock to get
   its real value.
 - The RTC prescaler is adjusted with this LSI frequency value so that the RTC
   CK_SPRE value become more accurate.
 - When calibration is done LED2 is turned ON to indicate the end of this operation.
 

@par Directory contents 

  - RTC/RTC_LSI/stm32f30x_conf.h    Library Configuration file
  - RTC/RTC_LSI/stm32f30x_it.c      Interrupt handlers
  - RTC/RTC_LSI/stm32f30x_it.h      Interrupt handlers header file
  - RTC/RTC_LSI/main.c              Main program
  - RTC/RTC_LSI/main.h              Main program header file
  - RTC/RTC_LSI/system_stm32f30x.c  STM32F30x system source file
  
@note The "system_stm32f30x.c" is generated by an automatic clock configuration 
      system and can be easily customized to your own configuration. 
      To select different clock setup, use the "STM32F30x_Clock_Configuration_V1.0.0.xls" 
      provided with the AN4152 package available on <a href="http://www.st.com/internet/mcu/family/141.jsp">  ST Microcontrollers </a>
 
@par Hardware and Software environment

  - This example runs on STM32F303xC and STM32F303xE Devices.
  
  - This example has been tested with STMicroelectronics STM32303C-EVAL (STM32F30x)
    evaluation board and can be easily tailored to any other supported device 
    and development board.
    
  - STM32303C-EVAL Set-up
    - Use the KEY push button connected to PE.06 pin (EXTI Line6)
    
@par How to use it ? 

In order to make the program work, you must do the following :
 - Copy all source files from this example folder to the template folder under
   Projects\STM32F30x_StdPeriph_Templates
 - Open your preferred toolchain 
 - Add the following file to the project source list
   - Utilities\STM32_EVAL\STM32303C_EVAL\stm32303c_eval.c
 - Rebuild all files and load your image into target memory
 - Run the example
    

 */
