void main(void)
{
RCC_ClocksTypeDef get_rcc_clock; //结构体
RCC_GetClocksFreq(&get_rcc_clock); //获取时钟信息
while(1)
{}
}
STM32F407自带结构体
stm32f4xx_rcc.h
/* Exported types ------------------------------------------------------------*/
typedef struct
{
uint32_t SYSCLK_Frequency; /*!< SYSCLK clock frequency expressed in Hz */
uint32_t HCLK_Frequency; /*!< HCLK clock frequency expressed in Hz */
uint32_t PCLK1_Frequency; /*!< PCLK1 clock frequency expressed in Hz */
uint32_t PCLK2_Frequency; /*!< PCLK2 clock frequency expressed in Hz */
}RCC_ClocksTypeDef;
stm32f4xx_rcc.c
/**
* @brief Returns the frequencies of different on chip clocks; SYSCLK, HCLK,
* PCLK1 and PCLK2.
*
* @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:
* @note If SYSCLK source is HSI, function returns values based on HSI_VALUE(*)
* @note If SYSCLK source is HSE, function returns values based on HSE_VALUE(**)
* @note If SYSCLK source is PLL, function returns values based on HSE_VALUE(**)
* or HSI_VALUE(*) multiplied/divided by the PLL factors.
* @note (*) HSI_VALUE is a constant defined in stm32f4xx.h file (default value
* 16 MHz) but the real value may vary depending on the variations
* in voltage and temperature.
* @note (**) HSE_VALUE is a constant defined in stm32f4xx.h file (default value
* 25 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.
*
* @note The result of this function could be not correct when using fractional
* value for HSE crystal.
*
* @param RCC_Clocks: pointer to a RCC_ClocksTypeDef structure which will hold
* the clocks frequencies.
*
* @note This function can be used by the user application to compute the
* baudrate for the communication peripherals or configure other parameters.
* @note Each time SYSCLK, HCLK, PCLK1 and/or PCLK2 clock changes, this function
* must be called to update the structure's field. Otherwise, any
* configuration based on this function will be incorrect.
*
* @retval None
*/
void RCC_GetClocksFreq(RCC_ClocksTypeDef* RCC_Clocks)
{
uint32_t tmp = 0, presc = 0, pllvco = 0, pllp = 2, pllsource = 0, pllm = 2;
/* Get SYSCLK source -------------------------------------------------------*/
tmp = RCC->CFGR & RCC_CFGR_SWS;
switch (tmp)
{
case 0x00: /* HSI used as system clock source */
RCC_Clocks->SYSCLK_Frequency = HSI_VALUE;
break;
case 0x04: /* HSE used as system clock source */
RCC_Clocks->SYSCLK_Frequency = HSE_VALUE;
break;
case 0x08: /* PLL used as system clock source */
/* PLL_VCO = (HSE_VALUE or HSI_VALUE / PLLM) * PLLN
SYSCLK = PLL_VCO / PLLP
*/
pllsource = (RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC) >> 22;
pllm = RCC->PLLCFGR & RCC_PLLCFGR_PLLM;
if (pllsource != 0)
{
/* HSE used as PLL clock source */
pllvco = (HSE_VALUE / pllm) * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6);
}
else
{
/* HSI used as PLL clock source */
pllvco = (HSI_VALUE / pllm) * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6);
}
pllp = (((RCC->PLLCFGR & RCC_PLLCFGR_PLLP) >>16) + 1 ) *2;
RCC_Clocks->SYSCLK_Frequency = pllvco/pllp;
break;
default:
RCC_Clocks->SYSCLK_Frequency = HSI_VALUE;
break;
}
/* Compute HCLK, PCLK1 and PCLK2 clocks frequencies ------------------------*/
/* Get HCLK prescaler */
tmp = RCC->CFGR & RCC_CFGR_HPRE;
tmp = tmp >> 4;
presc = APBAHBPrescTable[tmp];
/* HCLK clock frequency */
RCC_Clocks->HCLK_Frequency = RCC_Clocks->SYSCLK_Frequency >> presc;
/* Get PCLK1 prescaler */
tmp = RCC->CFGR & RCC_CFGR_PPRE1;
tmp = tmp >> 10;
presc = APBAHBPrescTable[tmp];
/* PCLK1 clock frequency */
RCC_Clocks->PCLK1_Frequency = RCC_Clocks->HCLK_Frequency >> presc;
/* Get PCLK2 prescaler */
tmp = RCC->CFGR & RCC_CFGR_PPRE2;
tmp = tmp >> 13;
presc = APBAHBPrescTable[tmp];
/* PCLK2 clock frequency */
RCC_Clocks->PCLK2_Frequency = RCC_Clocks->HCLK_Frequency >> presc;
}
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