STM32CubeF1/Projects/STM32F103RB-Nucleo/Examples_LL/RCC/RCC_UseHSI_PLLasSystemClock

/**
  @page RCC_UseHSI_PLLasSystemClock RCC example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    Examples_LL/RCC/RCC_UseHSI_PLLasSystemClock/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the RCC_UseHSI_PLLasSystemClock example.
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2016 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  @endverbatim

@par Example Description

Modification of the PLL parameters in run time.

In this example, the toggling frequency of the green LED2 depends on the system clock 
frequency and, each time the user-button is pressed, the PLL switches between two configurations.
This make the LED2 blinking speed to highlight the system clock frequency changes.

In this example, after start-up, SYSCLK is configured to the max frequency using the PLL with
HSE as clock source.
Then, at user-button press, an automatic switch is done between PLL with HSI as clock source (SYSCLK
set to 32MHz) and PLL with HSI as clock source (SYSCLK set to 64MHz). 
LED2 will toggle differently between the 2 configurations (quick toggle with HSI configuration at 64MHz).

To detect a problem with PLL configuration, switch USE_TIMEOUT can be enabled. Then in case of issues, 
LED2 will toggle every 1 second.
Note: "uwFrequency" variable can be added in LiveWatch to monitor the system clock frequency.


@par Directory contents 

  - RCC/RCC_UseHSI_PLLasSystemClock/Inc/stm32f1xx_it.h          Interrupt handlers header file
  - RCC/RCC_UseHSI_PLLasSystemClock/Inc/main.h                  Header for main.c module
  - RCC/RCC_UseHSI_PLLasSystemClock/Inc/stm32_assert.h          Template file to include assert_failed function
  - RCC/RCC_UseHSI_PLLasSystemClock/Src/stm32f1xx_it.c          Interrupt handlers
  - RCC/RCC_UseHSI_PLLasSystemClock/Src/main.c                  Main program
  - RCC/RCC_UseHSI_PLLasSystemClock/Src/system_stm32f1xx.c      STM32F1xx system source file


@par Hardware and Software environment

  - This example runs on STM32F103xB devices.
    
  - This example has been tested with STM32F103RB-Nucleo board and can be
    easily tailored to any other supported device and development board.


@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>
 */