File content as of revision 4:306609fe9dc8:

/*
  ******************************************************************************
  * @file    SysClockConf.c
  * @author  Zoltan Hudak
  * @version 
  * @date    05-July-2016
  * @brief   System Clock configuration for STM32F103C8T6
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; COPYRIGHT(c) 2016 Zoltan Hudak <hudakz@inbox.com>
  *
  * All rights reserved.

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

#include "SysClockConf.h"
#include "mbed.h"

bool HSE_SystemClock_Config(int freq) {
    RCC_OscInitTypeDef RCC_OscInitStruct;

    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
    RCC_OscInitStruct.HSEState = RCC_HSE_ON;
    RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
    switch(freq) {
    case 36:
        RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
        break;
    case 48:
        RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL6;
        break;
    default:
        RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
    }

    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
        return false;
    }

    RCC_ClkInitTypeDef RCC_ClkInitStruct;

    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                                |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK) {
        return false;
    }

    RCC_PeriphCLKInitTypeDef PeriphClkInit;

    PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC|RCC_PERIPHCLK_USB;
    switch(freq) {
    case 36:
        PeriphClkInit.AdcClockSelection = RCC_ADCPCLK2_DIV6;
        break;
    case 48:
        PeriphClkInit.AdcClockSelection = RCC_ADCPCLK2_DIV4;
        break;
    default:
        PeriphClkInit.AdcClockSelection = RCC_ADCPCLK2_DIV6;
    }
    PeriphClkInit.UsbClockSelection = RCC_USBPLLCLK_DIV1;
    if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK) {
        return false;
    }
    return true;
}

bool confSysClock(int freq) {
    HAL_RCC_DeInit();
    if (!HSE_SystemClock_Config(freq)) {
        return false;
    }
    SystemCoreClockUpdate();
    return true;
}