File content as of revision 0:a04710facbb6:

/* mbed Microcontroller Library
* Copyright (c) 2006-2017 ARM Limited
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

/**
  * This file configures the system clock as follows:
  *-----------------------------------------------------------------------------
  * System clock source                | 1- PLL_HSE_EXTC        | 3- PLL_HSI
  *                                    | (external 8 MHz clock) | (internal 8 MHz)
  *                                    | 2- PLL_HSE_XTAL        |
  *                                    | (external 8 MHz xtal)  |
  *-----------------------------------------------------------------------------
  * SYSCLK(MHz)                        | 72                     | 64
  *-----------------------------------------------------------------------------
  * AHBCLK (MHz)                       | 72                     | 64
  *-----------------------------------------------------------------------------
  * APB1CLK (MHz)                      | 36                     | 32
  *-----------------------------------------------------------------------------
  * APB2CLK (MHz)                      | 72                     | 64
  *-----------------------------------------------------------------------------
  * USB capable (48 MHz precise clock) | NO                     | NO
  *-----------------------------------------------------------------------------
  ******************************************************************************
  */

#include "stm32f1xx.h"

/*!< Uncomment the following line if you need to relocate your vector Table in
     Internal SRAM. */
/* #define VECT_TAB_SRAM */
#define VECT_TAB_OFFSET  0x00000000U /*!< Vector Table base offset field. 
                                  This value must be a multiple of 0x200. */


/* Select the clock sources (other than HSI) to start with (0=OFF, 1=ON) */
#define USE_PLL_HSE_EXTC (0) /* Use external clock */
#define USE_PLL_HSE_XTAL (1) /* Use external xtal */


#if (USE_PLL_HSE_XTAL != 0) || (USE_PLL_HSE_EXTC != 0)
uint8_t SetSysClock_PLL_HSE(uint8_t bypass);
#endif

uint8_t SetSysClock_PLL_HSI(void);


/**
  * @brief  Setup the microcontroller system
  *         Initialize the Embedded Flash Interface, the PLL and update the
  *         SystemCoreClock variable.
  * @note   This function should be used only after reset.
  * @param  None
  * @retval None
  */
void SystemInit (void)
{
    /* Reset the RCC clock configuration to the default reset state(for debug purpose) */
    /* Set HSION bit */
    RCC->CR |= 0x00000001U;

    /* Reset SW, HPRE, PPRE1, PPRE2, ADCPRE and MCO bits */
#if !defined(STM32F105xC) && !defined(STM32F107xC)
    RCC->CFGR &= 0xF8FF0000U;
#else
    RCC->CFGR &= 0xF0FF0000U;
#endif /* STM32F105xC */

    /* Reset HSEON, CSSON and PLLON bits */
    RCC->CR &= 0xFEF6FFFFU;

    /* Reset HSEBYP bit */
    RCC->CR &= 0xFFFBFFFFU;

    /* Reset PLLSRC, PLLXTPRE, PLLMUL and USBPRE/OTGFSPRE bits */
    RCC->CFGR &= 0xFF80FFFFU;

#if defined(STM32F105xC) || defined(STM32F107xC)
    /* Reset PLL2ON and PLL3ON bits */
    RCC->CR &= 0xEBFFFFFFU;

    /* Disable all interrupts and clear pending bits  */
    RCC->CIR = 0x00FF0000U;

    /* Reset CFGR2 register */
    RCC->CFGR2 = 0x00000000U;
#elif defined(STM32F100xB) || defined(STM32F100xE)
    /* Disable all interrupts and clear pending bits  */
    RCC->CIR = 0x009F0000U;

    /* Reset CFGR2 register */
    RCC->CFGR2 = 0x00000000U;
#else
    /* Disable all interrupts and clear pending bits  */
    RCC->CIR = 0x009F0000U;
#endif /* STM32F105xC */

#if defined(STM32F100xE) || defined(STM32F101xE) || defined(STM32F101xG) || defined(STM32F103xE) || defined(STM32F103xG)
#ifdef DATA_IN_ExtSRAM
    SystemInit_ExtMemCtl();
#endif /* DATA_IN_ExtSRAM */
#endif

#ifdef VECT_TAB_SRAM
    SCB->VTOR = SRAM_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal SRAM. */
#else
    SCB->VTOR = FLASH_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal FLASH. */
#endif

}

/**
  * @brief  Configures the System clock source, PLL Multiplier and Divider factors,
  *               AHB/APBx prescalers and Flash settings
  * @note   This function should be called only once the RCC clock configuration
  *         is reset to the default reset state (done in SystemInit() function).
  * @param  None
  * @retval None
  */
void SetSysClock(void)
{
    /* 1- Try to start with HSE and external clock */
#if USE_PLL_HSE_EXTC != 0
    if (SetSysClock_PLL_HSE(1) == 0)
#endif
    {
        /* 2- If fail try to start with HSE and external xtal */
#if USE_PLL_HSE_XTAL != 0
        if (SetSysClock_PLL_HSE(0) == 0)
#endif
        {
            /* 3- If fail start with HSI clock */
            if (SetSysClock_PLL_HSI() == 0) {
                while(1) {
                    // [TODO] Put something here to tell the user that a problem occured...
                }
            }
        }
    }

    /* Output clock on MCO1 pin(PA8) for debugging purpose */
    //HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_SYSCLK, RCC_MCODIV_1); // 72 MHz or 64 MHz
}

#if (USE_PLL_HSE_XTAL != 0) || (USE_PLL_HSE_EXTC != 0)
/******************************************************************************/
/*            PLL (clocked by HSE) used as System clock source                */
/******************************************************************************/
uint8_t SetSysClock_PLL_HSE(uint8_t bypass)
{
    RCC_ClkInitTypeDef RCC_ClkInitStruct;
    RCC_OscInitTypeDef RCC_OscInitStruct;

    /* Enable HSE oscillator and activate PLL with HSE as source */
    RCC_OscInitStruct.OscillatorType      = RCC_OSCILLATORTYPE_HSE;
    if (bypass == 0) {
        RCC_OscInitStruct.HSEState          = RCC_HSE_ON; /* External 8 MHz xtal on OSC_IN/OSC_OUT */
    } else {
        RCC_OscInitStruct.HSEState          = RCC_HSE_BYPASS; /* External 8 MHz clock on OSC_IN */
    }
    RCC_OscInitStruct.HSEPredivValue      = RCC_HSE_PREDIV_DIV1;
    RCC_OscInitStruct.PLL.PLLState        = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource       = RCC_PLLSOURCE_HSE;
    RCC_OscInitStruct.PLL.PLLMUL          = RCC_PLL_MUL9; // 72 MHz (8 MHz * 9)
    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
        return 0; // FAIL
    }

    /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers */
    RCC_ClkInitStruct.ClockType      = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
    RCC_ClkInitStruct.SYSCLKSource   = RCC_SYSCLKSOURCE_PLLCLK; // 72 MHz
    RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 72 MHz
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           // 36 MHz
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 72 MHz
    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK) {
        return 0; // FAIL
    }

    /* Output clock on MCO1 pin(PA8) for debugging purpose */
    //HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSE, RCC_MCODIV_1); // 8 MHz

    return 1; // OK
}
#endif

/******************************************************************************/
/*            PLL (clocked by HSI) used as System clock source                */
/******************************************************************************/
uint8_t SetSysClock_PLL_HSI(void)
{
    RCC_ClkInitTypeDef RCC_ClkInitStruct;
    RCC_OscInitTypeDef RCC_OscInitStruct;

    /* Enable HSI oscillator and activate PLL with HSI as source */
    RCC_OscInitStruct.OscillatorType      = RCC_OSCILLATORTYPE_HSI | RCC_OSCILLATORTYPE_HSE;
    RCC_OscInitStruct.HSIState            = RCC_HSI_ON;
    RCC_OscInitStruct.HSEState            = RCC_HSE_OFF;
    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
    RCC_OscInitStruct.PLL.PLLState        = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource       = RCC_PLLSOURCE_HSI_DIV2;
    RCC_OscInitStruct.PLL.PLLMUL          = RCC_PLL_MUL16; // 64 MHz (8 MHz/2 * 16)
    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
        return 0; // FAIL
    }

    /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers */
    RCC_ClkInitStruct.ClockType      = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
    RCC_ClkInitStruct.SYSCLKSource   = RCC_SYSCLKSOURCE_PLLCLK; // 64 MHz
    RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 64 MHz
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           // 32 MHz
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 64 MHz
    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK) {
        return 0; // FAIL
    }

    /* Output clock on MCO1 pin(PA8) for debugging purpose */
    //HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSI, RCC_MCODIV_1); // 8 MHz

    return 1; // OK
}