/**
  ******************************************************************************
  * @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.
  *
  *
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2016 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.
  *
  ******************************************************************************
  */
/** @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; then 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.
  *
  *           - If SYSCLK source is HSI48, SystemCoreClock will contain the HSI48_VALUE(***)
  *
  *         (*) HSI_VALUE is a constant defined in stm32f0xx_hal_conf.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_conf.h file (its value
  *              depends on the application requirements), user has to ensure that HSE_VALUE
  *              is same as the real frequency of the crystal used. Otherwise, this function
  *              may have wrong result.
  *
  *         (***) HSI48_VALUE is a constant defined in stm32f0xx_hal_conf.h file (default value
  *             48 MHz) but the real value may vary depending on the variations
  *             in voltage and temperature.
  *
  *         - 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(STM32F071xB) || 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 || STM32F071xB || 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;
}

/**
  * @}
  */

/**
  * @}
  */

/**
  * @}
  */

