/**
  @page CRS_Synchronization_Polling CRS example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    Examples_LL/CRS/CRS_Synchronization_Polling/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the CRS_Synchronization_Polling example.
  ******************************************************************************
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  @endverbatim

@par Example Description

This example describes how to configure Clock Recovery Service in polling mode through 
the STM32F0xx CRS LL API. Peripheral initialization done using 
LL unitary services functions for optimization purpose (performance and size).

At the beginning of the main program the SystemClock_Config() function is used to 
configure the system clock (SYSCLK) to run at 48 MHz.

Then, HSI48 and LSE oscillators are enabled. In this example CRS will use LSE 
oscillator to calibrate HSI48 frequency.
When HSI48 and LSE are started, automatic calibration starts and program call the
polling function to wait for synchronization status.

In this test, there are results which could occur:
 - Wait for User push-button press to start the test (Fast toggle LED2)
 - few loops occurs up to SYNC OK event (if SYNC WARN, HSI48 trimming value will be
 automatically modified)
 - in case of SYNC MISS or SYNC ERROR, there is an issue with synchronization input
 parameters. In this case, user need to apply new parameters after checking synchronization
 information and restart the synchronization.
 - LED2 is slowly blinking (1 sec. period) in case of timeout during polling 
 procedure. It may due to an issue with LSE synchronization frequency.
 - LED2 will finally power on if SYNC OK is returned by CRS.
 
@par Directory contents 

  - CRS/CRS_Synchronization_Polling/Inc/stm32f0xx_it.h          Interrupt handlers header file
  - CRS/CRS_Synchronization_Polling/Inc/main.h                  Header for main.c module
  - CRS/CRS_Synchronization_Polling/Inc/stm32_assert.h          Template file to include assert_failed function
  - CRS/CRS_Synchronization_Polling/Src/stm32f0xx_it.c          Interrupt handlers
  - CRS/CRS_Synchronization_Polling/Src/main.c                  Main program
  - CRS/CRS_Synchronization_Polling/Src/system_stm32f0xx.c      STM32F0xx system source file


@par Hardware and Software environment

  - This example runs on STM32F072xB devices.
    
  - This example has been tested with STM32F072RB-Nucleo RevC board and can be
    easily tailored to any other supported device and development board.

  - STM32F072RB-Nucleo RevC Set-up
    - Connect the MCO pin to an oscilloscope to monitor HSI48 frequency:
      - PA.08: connected to pin 23 of CN10 connector  


@par How to use it ? 

In order to make the program work, you must do the following :
 - Open your preferred toolchain
 - Rebuild all files and load your image into target memory
 - Run the example

 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */
