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configure system clock using registers for stm32f030k6t6

jdo
Associate II

0693W00000QNZsmQAH.jpgI need to configure the system clock using registers for 48mhz without external crystal, I already have it configured and tested with stmcube ide manager, but I need to decrease the flash memory and ram, as they are critical.

i have this configuration step for 32mhz, but with external crystal:

/* 32MHz HSI PLL Configuration */
		RCC->CR &= ~RCC_CR_PLLON; /* Keep PLL off */
 
		RCC->CFGR &= ~RCC_CFGR_PLLSRC_Msk;
		RCC->CFGR |= RCC_CFGR_PLLSRC_HSI_DIV2;
 
		RCC->CFGR &= ~RCC_CFGR_PLLMUL_Msk;
		RCC->CFGR |= RCC_CFGR_PLLMUL8;
 
		RCC->CR |= RCC_CR_PLLON; /* Turn PLL on */
		while ((RCC->CR & RCC_CR_PLLRDY) == 0); /* Wait for PLL to be ready */
 
		RCC->CFGR &= ~RCC_CFGR_HPRE_Msk; /* Clear AHB resister */
		RCC->CFGR |= RCC_CFGR_HPRE_DIV1; /* AHB Prescaler */
 
		RCC->CFGR &= ~RCC_CFGR_PPRE_Msk; /* Clear APB1 resister */
		RCC->CFGR |= RCC_CFGR_PPRE_DIV1; /* APB1 Prescaler */
 
		RCC->CFGR &= ~RCC_CFGR_SW_Msk; /* Clear SW resister */
		RCC->CFGR |= RCC_CFGR_SW_PLL; /* Set PLL as system clock */

find in the internet the step for configure clock is:

1._ ENABLE HSI and wait for the HSI to become Ready

2._ Set the POWER ENABLE CLOCK and VOLTAGE REGULATOR

3._Configure the FLASH PREFETCH and the LATENCY Related Settings

4._Configure the PRESCALARS HCLK, PCLK1

5._Configure the MAIN PLL

6._ Enable the PLL and wait for it to become ready

7._Select the Clock Source and wait for it to be set

THE STEP ONE I DON´T KNOW THIS IS RIGTH.

3 REPLIES 3
gbm
Lead III
  1. Don't enable HSI - it's already enabled after reset.
  2. Set the PLL parameters in RCC->CFGR
  3. enable PLL in RCC->CR
  4. wait for PLL stabiized
  5. set Flash wait states
  6. Switch to PLL clock

This makes 5 lines of code total

My STM32 stuff on github - compact USB device stack and more: https://github.com/gbm-ii/gbmUSBdevice
jdo
Associate II

i am using the SystemInit() generated for excel macro

 
/** @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
  * @{
  */
static void SetSysClock(void);
/**
  * @}
  */
 
/** @addtogroup STM32F0xx_System_Private_Functions
  * @{
  */
 
/**
  * @brief  Setup the microcontroller system
  * @param  None
  * @retval None
  */
void SystemInit(void)
{
	/* Set HSION bit */
	  RCC->CR |= (uint32_t)0x00000001;
 
	  /* Reset SW[1:0], HPRE[3:0], PPRE[2:0], ADCPRE and MCOSEL[2:0] bits */
	  RCC->CFGR &= (uint32_t)0xF8FFB80C;
 
	  /* Reset HSEON, CSSON and PLLON bits */
	  RCC->CR &= (uint32_t)0xFEF6FFFF;
 
	  /* Reset HSEBYP bit */
	  RCC->CR &= (uint32_t)0xFFFBFFFF;
 
	  /* Reset PLLSRC, PLLXTPRE and PLLMUL[3:0] bits */
	  RCC->CFGR &= (uint32_t)0xFFC0FFFF;
 
	  /* Reset PREDIV1[3:0] bits */
	  RCC->CFGR2 &= (uint32_t)0xFFFFFFF0;
 
	  /* Reset USARTSW[1:0], I2CSW, CECSW and ADCSW bits */
	  RCC->CFGR3 &= (uint32_t)0xFFFFFEAC;
 
	  /* Reset HSI14 bit */
	  RCC->CR2 &= (uint32_t)0xFFFFFFFE;
 
	  /* Disable all interrupts */
	  RCC->CIR = 0x00000000;
 
	  /* Configure the System clock frequency, AHB/APBx prescalers and Flash settings */
	  SetSysClock();
}
 
/**
   * @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.
  *
  *         (*) 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.
  *
  *         - 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(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 || 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;
}
 
static void SetSysClock(void)
{
/******************************************************************************/
/*            PLL (clocked by HSI) used as System clock source                */
/******************************************************************************/
 
  /* At this stage the HSI is already enabled and used as System clock source */
 
  /* SYSCLK, HCLK, PCLK configuration ----------------------------------------*/
 
    /* Enable Prefetch Buffer and set Flash Latency */
    FLASH->ACR = FLASH_ACR_PRFTBE | FLASH_ACR_LATENCY;
 
     /* HCLK = SYSCLK / 1 */
     RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;
 
     /* PCLK = HCLK / 1 */
     RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE_DIV1;
 
  /* PLL configuration */
    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE ));
    RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_HSI_DIV2 | RCC_CFGR_PLLXTPRE_Pos);
 
  /* Enable PLL */
  RCC->CR |= RCC_CR_PLLON;
 
  /* Wait till PLL is ready */
  while((RCC->CR & RCC_CR_PLLRDY) == 0)
  {
  }
 
  /* Select PLL as system clock source */
  RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
  RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL;
 
  /* Wait till PLL is used as system clock source */
  while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)RCC_CFGR_SWS_PLL)
  {
  }
}
 
 
/**
  * @}
  */
 
/**
  * @}
  */
 
/**
  * @}
  */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
 
 

the main code is:

i want view led blink in PA12, but i don´t view blink, the led is fixed on.

jdo
Associate II

excuse me not resume the code,

#include <stdint.h>
#include <stm32f0xx.h>
 
 
 
/*
#if !defined(__SOFT_FP__) && defined(__ARM_FP)
  #warning "FPU is not initialized, but the project is compiling for an FPU. Please initialize the FPU before use."
#endif
*/
 
void systme_clk()
{
 
	/* 48 Mhz HSI PLL configuration */
	/**************************************************************/
	// HSI RC
	// HSI PLL ON
	// CONFIGURATE PLL MULTIPLEXOR
	//
 
	/*************************************************************/
 
 
	/* 32MHz HSI PLL Configuration */
		RCC->CR &= ~RCC_CR_PLLON; /* Keep PLL off */
 
		RCC->CFGR &= ~RCC_CFGR_PLLSRC_Msk;
		RCC->CFGR |= RCC_CFGR_PLLSRC_HSI_DIV2;
 
		RCC->CFGR &= ~RCC_CFGR_PLLMUL_Msk;
		RCC->CFGR |= RCC_CFGR_PLLMUL8;
 
		RCC->CR |= RCC_CR_PLLON; /* Turn PLL on */
		while ((RCC->CR & RCC_CR_PLLRDY) == 0); /* Wait for PLL to be ready */
 
		RCC->CFGR &= ~RCC_CFGR_HPRE_Msk; /* Clear AHB resister */
		RCC->CFGR |= RCC_CFGR_HPRE_DIV1; /* AHB Prescaler */
 
		RCC->CFGR &= ~RCC_CFGR_PPRE_Msk; /* Clear APB1 resister */
		RCC->CFGR |= RCC_CFGR_PPRE_DIV1; /* APB1 Prescaler */
 
		RCC->CFGR &= ~RCC_CFGR_SW_Msk; /* Clear SW resister */
		RCC->CFGR |= RCC_CFGR_SW_PLL; /* Set PLL as system clock */
}
void GPIO_Init(void)
{
	RCC->AHBENR |= RCC_AHBENR_GPIOAEN; /* Enable GPIOA clock */
	GPIOA->MODER |= (1<<24);  // pin PA12(bits 11:10) as Output (01)
	GPIOA->OTYPER &= ~(1<<12);  // bit 12=0 --> Output push pull
	GPIOA->OSPEEDR |= (1<<25);  // Pin PA12 (bits 25:24) as Fast Speed (1:0)
	GPIOA->PUPDR &= ~((1<<24) | (1<<25));  // Pin PA12 (bits 25:24) are 0:0 --> no pull up or pulldown
 
 
 
	//RGB_DATA_GPIO_Port->MODER |= 0x02U << (RGB_DATA_Pin << 1); /* Alternate function mode */
	//RGB_DATA_GPIO_Port->AFR[11] |= 5U << (RGB_DATA_Pin << 2); /* Alternate function (TIM16_CH1 AF5) */
	//RGB_DATA_GPIO_Port->OSPEEDR |= 0b11 << (RGB_DATA_Pin << 1); /* output high-speed */
}
void Delay(uint32_t time)
{
	while(time--);
}
 
 
int main(void)
{
 
	//systme_clk();
	SystemInit();
 
	GPIO_Init();
 
 
 
    /* Loop forever */
		while(1)
		{
			//GPIOA->BSRR |= (1<<12); // Set the Pin PA12
					GPIOA->ODR = 1<<12;
					Delay (100000000);  // random delay
			//		GPIOA->BSRR |= (1<<5) <<16;  // Clear the Pin PA5
					GPIOA->ODR &= ~(1<<12);
					Delay (100000000);  // random delay
 
		}
}