STM32C011 Clock Config

[saraacri]

Hi @ST Community ,

I struggle to configure the clock speed to the frequency I desire.

The chip I am using is STM32C011F6U and the code I use as first function in main() is the following:

uint16_t cr = RCC->CR;
uint16_t cal = RCC->ICSCR;
uint16_t cfgr = RCC->CFGR;

//Reset Clock divider to 1 (full 48MHz)
cr &= ~(RCC_CR_HSIDIV_0 | RCC_CR_HSIDIV_1 | RCC_CR_HSIDIV_2);
cr |= (1U << 11);
cr |= (1U << 12);
cr |= (1U << 13);
RCC->CR = cr;

//Enable HSI48 Clock
RCC->CR |= RCC_CR_HSION;

//Wait for HSI to be ready
while((RCC->CR &= RCC_CR_HSIRDY) == 0u);

//Default HSI calibration trimming value
cal &= ~RCC_ICSCR_HSITRIM;
cal |= RCC_ICSCR_HSITRIM_6;
RCC->ICSCR = cal;

//Set APB divider to 8
cfgr &= ~RCC_CFGR_PPRE;
cfgr |= (RCC_CFGR_PPRE_2 | RCC_CFGR_PPRE_1);
RCC->CFGR = cfgr;

//Set AHB divider to 1
cfgr &= ~RCC_CFGR_HPRE;
RCC->CFGR = cfgr;

However the above doesn't seem to have any effect and the clock frequency never change. I have also tried to output the SYSCLK using the MCO pins.

What am I doing wrong or missing?

Thanks!

[AScha.3 · Accepted solution]

make a project with CubeMX , set clock tree as you want it, generate code -> and look there, what you should write

[EXUE.2]

the normal clock configuration is as below in our example and CubeMX, you also can get the official example project in ST official website.

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSIDiv = RCC_HSI_DIV1;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
  {
    Error_Handler();
  }
}