STM32CubeF4

@verbatim
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
* @file Examples_LL/RCC/RCC_UseHSI_PLLasSystemClock/readme.txt
* @author MCD Application Team
* @brief Description of the RCC_UseHSI_PLLasSystemClock example.
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@par Example Description

This example shows how to modify 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 40MHz) and PLL with HSI as clock source (SYSCLK set to 100MHz).
LED2 will toggle differently between the 2 configurations (quick toggle with HSI configuration at 100MHz).

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 Keywords

System, RCC, PLL, PLLCLK, SYSCLK, HSE, Clock, Oscillator, HSI

@par Directory contents

- RCC/RCC_UseHSI_PLLasSystemClock/Inc/stm32f4xx_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/stm32f4xx_it.c Interrupt handlers
- RCC/RCC_UseHSI_PLLasSystemClock/Src/main.c Main program
- RCC/RCC_UseHSI_PLLasSystemClock/Src/system_stm32f4xx.c STM32F4xx system source file

@par Hardware and Software environment

- This example runs on STM32F411xE devices.

- This example has been tested with NUCLEO-F411RE 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