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/**

  ******************************************************************************

  * @file    system_stm32f0xx.c

  * @author  MCD Application Team

  * @brief   CMSIS Cortex-M0 Device Peripheral Access Layer System Source File.

  *

  * 1. This file provides two functions and one global variable to be called from

  *    user application:

  *      - SystemInit(): This function is called at startup just after reset and

  *                      before branch to main program. This call is made inside

  *                      the "startup_stm32f0xx.s" file.

  *

  *      - SystemCoreClock variable: Contains the core clock (HCLK), it can be used

  *                                  by the user application to setup the SysTick

  *                                  timer or configure other parameters.

  *

  *      - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must

  *                                 be called whenever the core clock is changed

  *                                 during program execution.

  *

  * 2. After each device reset the HSI (8 MHz) is used as system clock source.

  *    Then SystemInit() function is called, in "startup_stm32f0xx.s" file, to

  *    configure the system clock before to branch to main program.

  *

  * 3. This file configures the system clock as follows:

  *=============================================================================

  *                         Supported STM32F0xx device

  *-----------------------------------------------------------------------------

  *        System Clock source                    | HSI

  *-----------------------------------------------------------------------------

  *        SYSCLK(Hz)                             | 8000000

  *-----------------------------------------------------------------------------

  *        HCLK(Hz)                               | 8000000

  *-----------------------------------------------------------------------------

  *        AHB Prescaler                          | 1

  *-----------------------------------------------------------------------------

  *        APB1 Prescaler                         | 1

  *-----------------------------------------------------------------------------

  *=============================================================================

  ******************************************************************************

  * @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

  *

  ******************************************************************************

  */

/** @addtogroup CMSIS

  * @{

  */

/** @addtogroup stm32f0xx_system

  * @{

  */

/** @addtogroup STM32F0xx_System_Private_Includes

  * @{

  */

#include "stm32f0xx.h"

/**

  * @}

  */

/** @addtogroup STM32F0xx_System_Private_TypesDefinitions

  * @{

  */

/**

  * @}

  */

/** @addtogroup STM32F0xx_System_Private_Defines

  * @{

  */

#if !defined  (HSE_VALUE) 

  #define HSE_VALUE    ((uint32_t)8000000) /*!< Default value of the External oscillator in Hz.

                                                This value can be provided and adapted by the user application. */

#endif /* HSE_VALUE */

#if !defined  (HSI_VALUE)

  #define HSI_VALUE    ((uint32_t)8000000) /*!< Default value of the Internal oscillator in Hz.

                                                This value can be provided and adapted by the user application. */

#endif /* HSI_VALUE */

#if !defined (HSI48_VALUE)

#define HSI48_VALUE    ((uint32_t)48000000) /*!< Default value of the HSI48 Internal oscillator in Hz.

                                                 This value can be provided and adapted by the user application. */

#endif /* HSI48_VALUE */

/**

  * @}

  */

/** @addtogroup STM32F0xx_System_Private_Macros

  * @{

  */

/**

  * @}

  */

/** @addtogroup STM32F0xx_System_Private_Variables

  * @{

  */

  /* This variable is updated in three ways:

      1) by calling CMSIS function SystemCoreClockUpdate()

      2) by calling HAL API function HAL_RCC_GetHCLKFreq()

      3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency

         Note: If you use this function to configure the system clock there is no need to

               call the 2 first functions listed above, since SystemCoreClock variable is

               updated automatically.

  */

uint32_t SystemCoreClock = 8000000;

const uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};

const uint8_t APBPrescTable[8]  = {0, 0, 0, 0, 1, 2, 3, 4};

/**

  * @}

  */

/** @addtogroup STM32F0xx_System_Private_FunctionPrototypes

  * @{

  */

/**

  * @}

  */

/** @addtogroup STM32F0xx_System_Private_Functions

  * @{

  */

/**

  * @brief  Setup the microcontroller system.

  * @param  None

  * @retval None

  */

void SystemInit(void)

{

  /* NOTE :SystemInit(): This function is called at startup just after reset and

                         before branch to main program. This call is made inside

                         the "startup_stm32f0xx.s" file.

                         User can setups the default system clock (System clock source, PLL Multiplier

                         and Divider factors, AHB/APBx prescalers and Flash settings).

   */

}

/**

   * @brief  Update SystemCoreClock variable according to Clock Register Values.

  *         The SystemCoreClock variable contains the core clock (HCLK), it can

  *         be used by the user application to setup the SysTick timer or configure

  *         other parameters.

  *

  * @note   Each time the core clock (HCLK) changes, this function must be called

  *         to update SystemCoreClock variable value. Otherwise, any configuration

  *         based on this variable will be incorrect.

  *

  * @note   - The system frequency computed by this function is not the real

  *           frequency in the chip. It is calculated based on the predefined

  *           constant and the selected clock source:

  *

  *           - If SYSCLK source is HSI, SystemCoreClock will contain the HSI_VALUE(*)

  *

  *           - If SYSCLK source is HSE, SystemCoreClock will contain the HSE_VALUE(**)

  *

  *           - If SYSCLK source is PLL, SystemCoreClock will contain the HSE_VALUE(**)

  *             or HSI_VALUE(*) multiplied/divided by the PLL factors.

  *

  *         (*) HSI_VALUE is a constant defined in stm32f0xx_hal.h file (default value

  *             8 MHz) but the real value may vary depending on the variations

  *             in voltage and temperature.

  *

  *         (**) HSE_VALUE is a constant defined in stm32f0xx_hal.h file (default value

  *              8 MHz), user has to ensure that HSE_VALUE is same as the real

  *              frequency of the crystal used. Otherwise, this function may

  *              have wrong result.

  *

  *         - The result of this function could be not correct when using fractional

  *           value for HSE crystal.

  *

  * @param  None

  * @retval None

  */

void SystemCoreClockUpdate (void)

{

  uint32_t tmp = 0, pllmull = 0, pllsource = 0, predivfactor = 0;

  /* Get SYSCLK source -------------------------------------------------------*/

  tmp = RCC->CFGR & RCC_CFGR_SWS;

  switch (tmp)

  {

    case RCC_CFGR_SWS_HSI:  /* HSI used as system clock */

      SystemCoreClock = HSI_VALUE;

      break;

    case RCC_CFGR_SWS_HSE:  /* HSE used as system clock */

      SystemCoreClock = HSE_VALUE;

      break;

    case RCC_CFGR_SWS_PLL:  /* PLL used as system clock */

      /* Get PLL clock source and multiplication factor ----------------------*/

      pllmull = RCC->CFGR & RCC_CFGR_PLLMUL;

      pllsource = RCC->CFGR & RCC_CFGR_PLLSRC;

      pllmull = ( pllmull >> 18) + 2;

      predivfactor = (RCC->CFGR2 & RCC_CFGR2_PREDIV) + 1;

      if (pllsource == RCC_CFGR_PLLSRC_HSE_PREDIV)

      {

        /* HSE used as PLL clock source : SystemCoreClock = HSE/PREDIV * PLLMUL */

        SystemCoreClock = (HSE_VALUE/predivfactor) * pllmull;

      }

#if defined(STM32F042x6) || defined(STM32F048xx) || defined(STM32F072xB) || defined(STM32F078xx) || defined(STM32F091xC) || defined(STM32F098xx)

      else if (pllsource == RCC_CFGR_PLLSRC_HSI48_PREDIV)

      {

        /* HSI48 used as PLL clock source : SystemCoreClock = HSI48/PREDIV * PLLMUL */

        SystemCoreClock = (HSI48_VALUE/predivfactor) * pllmull;

      }

#endif /* STM32F042x6 || STM32F048xx || STM32F072xB || STM32F078xx || STM32F091xC || STM32F098xx */

      else

      {

#if defined(STM32F042x6) || defined(STM32F048xx)  || defined(STM32F070x6) \

 || defined(STM32F078xx) || defined(STM32F071xB)  || defined(STM32F072xB) \

 || defined(STM32F070xB) || defined(STM32F091xC) || defined(STM32F098xx)  || defined(STM32F030xC)

        /* HSI used as PLL clock source : SystemCoreClock = HSI/PREDIV * PLLMUL */

        SystemCoreClock = (HSI_VALUE/predivfactor) * pllmull;

#else

        /* HSI used as PLL clock source : SystemCoreClock = HSI/2 * PLLMUL */

        SystemCoreClock = (HSI_VALUE >> 1) * pllmull;

#endif /* STM32F042x6 || STM32F048xx || STM32F070x6 || 

          STM32F071xB || STM32F072xB || STM32F078xx || STM32F070xB ||

          STM32F091xC || STM32F098xx || STM32F030xC */

      }

      break;

    default: /* HSI used as system clock */

      SystemCoreClock = HSI_VALUE;

      break;

  }

  /* Compute HCLK clock frequency ----------------*/

  /* Get HCLK prescaler */

  tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];

  /* HCLK clock frequency */

  SystemCoreClock >>= tmp;

}

/**

  * @}

  */

/**

  * @}

  */

/**

  * @}

  */

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