技術標籤：MCU

STM32獲取系統時鐘源和系統時鐘分配情況

一、相關庫函式

• ST官方提供了一些函式介面可以用來獲取系統時鐘的資訊

• 獲取系統當前使用的時鐘源

stm32f10x_rcc.c

/**
  * @brief  Returns the clock source used as system clock.
  * @param  None
  * @retval The clock source used as system clock. The returned value can
  *   be one of the following:
  *     - 0x00: HSI used as system clock
  *     - 0x04: HSE used as system clock
  *     - 0x08: PLL used as system clock
  */
 

uint8_t RCC_GetSYSCLKSource(void)
{
  return ((uint8_t)(RCC->CFGR & CFGR_SWS_Mask));
}

• 獲取系統不同部分時鐘的分配情況

stm32f10x_rcc.c

typedef struct
{
  uint32_t SYSCLK_Frequency;  /*!< returns SYSCLK clock frequency expressed in Hz */
  uint32_t HCLK_Frequency;    /*!< returns HCLK clock frequency expressed in Hz */
 

  uint32_t PCLK1_Frequency;   /*!< returns PCLK1 clock frequency expressed in Hz */
  uint32_t PCLK2_Frequency;   /*!< returns PCLK2 clock frequency expressed in Hz */
  uint32_t ADCCLK_Frequency;  /*!< returns ADCCLK clock frequency expressed in Hz */
}RCC_ClocksTypeDef;

/**
  * @brief  Returns the frequencies of different on chip clocks.
  * @param  RCC_Clocks: pointer to a RCC_ClocksTypeDef structure which will hold
  *         the clocks frequencies.
  * @note   The result of this function could be not correct when using 
  *         fractional value for HSE crystal.  
  * @retval None
  */
 

void RCC_GetClocksFreq(RCC_ClocksTypeDef* RCC_Clocks)
{
  uint32_t tmp = 0, pllmull = 0, pllsource = 0, presc = 0;

#ifdef  STM32F10X_CL
  uint32_t prediv1source = 0, prediv1factor = 0, prediv2factor = 0, pll2mull = 0;
#endif /* STM32F10X_CL */

#if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || defined (STM32F10X_HD_VL)
  uint32_t prediv1factor = 0;
#endif
    
  /* Get SYSCLK source -------------------------------------------------------*/
  tmp = RCC->CFGR & CFGR_SWS_Mask;
  
  switch (tmp)
  {
    case 0x00:  /* HSI used as system clock */
      RCC_Clocks->SYSCLK_Frequency = HSI_VALUE;
      break;
    case 0x04:  /* HSE used as system clock */
      RCC_Clocks->SYSCLK_Frequency = HSE_VALUE;
      break;
    case 0x08:  /* PLL used as system clock */

      /* Get PLL clock source and multiplication factor ----------------------*/
      pllmull = RCC->CFGR & CFGR_PLLMull_Mask;
      pllsource = RCC->CFGR & CFGR_PLLSRC_Mask;
      
#ifndef STM32F10X_CL      
      pllmull = ( pllmull >> 18) + 2;
      
      if (pllsource == 0x00)
      {/* HSI oscillator clock divided by 2 selected as PLL clock entry */
        RCC_Clocks->SYSCLK_Frequency = (HSI_VALUE >> 1) * pllmull;
      }
      else
      {
 #if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || defined (STM32F10X_HD_VL)
       prediv1factor = (RCC->CFGR2 & CFGR2_PREDIV1) + 1;
       /* HSE oscillator clock selected as PREDIV1 clock entry */
       RCC_Clocks->SYSCLK_Frequency = (HSE_VALUE / prediv1factor) * pllmull; 
 #else
        /* HSE selected as PLL clock entry */
        if ((RCC->CFGR & CFGR_PLLXTPRE_Mask) != (uint32_t)RESET)
        {/* HSE oscillator clock divided by 2 */
          RCC_Clocks->SYSCLK_Frequency = (HSE_VALUE >> 1) * pllmull;
        }
        else
        {
          RCC_Clocks->SYSCLK_Frequency = HSE_VALUE * pllmull;
        }
 #endif
      }
#else
      pllmull = pllmull >> 18;
      
      if (pllmull != 0x0D)
      {
         pllmull += 2;
      }
      else
      { /* PLL multiplication factor = PLL input clock * 6.5 */
        pllmull = 13 / 2; 
      }
            
      if (pllsource == 0x00)
      {/* HSI oscillator clock divided by 2 selected as PLL clock entry */
        RCC_Clocks->SYSCLK_Frequency = (HSI_VALUE >> 1) * pllmull;
      }
      else
      {/* PREDIV1 selected as PLL clock entry */
        
        /* Get PREDIV1 clock source and division factor */
        prediv1source = RCC->CFGR2 & CFGR2_PREDIV1SRC;
        prediv1factor = (RCC->CFGR2 & CFGR2_PREDIV1) + 1;
        
        if (prediv1source == 0)
        { /* HSE oscillator clock selected as PREDIV1 clock entry */
          RCC_Clocks->SYSCLK_Frequency = (HSE_VALUE / prediv1factor) * pllmull;          
        }
        else
        {/* PLL2 clock selected as PREDIV1 clock entry */
          
          /* Get PREDIV2 division factor and PLL2 multiplication factor */
          prediv2factor = ((RCC->CFGR2 & CFGR2_PREDIV2) >> 4) + 1;
          pll2mull = ((RCC->CFGR2 & CFGR2_PLL2MUL) >> 8 ) + 2; 
          RCC_Clocks->SYSCLK_Frequency = (((HSE_VALUE / prediv2factor) * pll2mull) / prediv1factor) * pllmull;                         
        }
      }
#endif /* STM32F10X_CL */ 
      break;

    default:
      RCC_Clocks->SYSCLK_Frequency = HSI_VALUE;
      break;
  }

  /* Compute HCLK, PCLK1, PCLK2 and ADCCLK clocks frequencies ----------------*/
  /* Get HCLK prescaler */
  tmp = RCC->CFGR & CFGR_HPRE_Set_Mask;
  tmp = tmp >> 4;
  presc = APBAHBPrescTable[tmp];
  /* HCLK clock frequency */
  RCC_Clocks->HCLK_Frequency = RCC_Clocks->SYSCLK_Frequency >> presc;
  /* Get PCLK1 prescaler */
  tmp = RCC->CFGR & CFGR_PPRE1_Set_Mask;
  tmp = tmp >> 8;
  presc = APBAHBPrescTable[tmp];
  /* PCLK1 clock frequency */
  RCC_Clocks->PCLK1_Frequency = RCC_Clocks->HCLK_Frequency >> presc;
  /* Get PCLK2 prescaler */
  tmp = RCC->CFGR & CFGR_PPRE2_Set_Mask;
  tmp = tmp >> 11;
  presc = APBAHBPrescTable[tmp];
  /* PCLK2 clock frequency */
  RCC_Clocks->PCLK2_Frequency = RCC_Clocks->HCLK_Frequency >> presc;
  /* Get ADCCLK prescaler */
  tmp = RCC->CFGR & CFGR_ADCPRE_Set_Mask;
  tmp = tmp >> 14;
  presc = ADCPrescTable[tmp];
  /* ADCCLK clock frequency */
  RCC_Clocks->ADCCLK_Frequency = RCC_Clocks->PCLK2_Frequency / presc;
}

二、程式碼參考

typedef struct
{
    u8 sys_clk_src;                             //檢視系統時鐘使用的時鐘源：0x00：HSI  0x04:HSE  0x08：PLL
    RCC_ClocksTypeDef RCC_Clocks;               //存放系統時鐘分配資訊
}sys_clk_info_stu_t;

/******************************************************************************
 * @Function: get_sys_clk_info
 * @Description: 獲取當前系統的時鐘資訊
 * @Input: sys_clk_info：存放時鐘分配資訊的結構體地址
 * @Output: None
 * @Return: void
 * @Others: None
 * @param {sys_clk_info_stu_t} *sys_clk_info
*******************************************************************************/
void get_sys_clk_info(sys_clk_info_stu_t *sys_clk_info)
{
    sys_clk_info->sys_clk_src = RCC_GetSYSCLKSource();
    RCC_GetClocksFreq(&(sys_clk_info->RCC_Clocks));
}

三、效果展示

說明：從結果可以知道系統的時鐘源來源於PLL，系統時鐘頻率為72M，AHB匯流排時鐘為72M，APB1匯流排時鐘為36M，APB2匯流排時鐘為72M，ADC時鐘為36M。