How to modify the external crystal frequency and configure PLL for stm32duino?

[Star]

Hi, my Arduino IDE has stm32duino installed. I want to use the board of STM32F407, but I know that some boards use external crystal 25MHz and some use 8MHz. So if I want to configure the clock properly, where should I configure the PLL parameters?

[ag123]

you need to define your own

Code: Select all

void SystemClock_Config(void)

in your variant, you can look at examples from existing variants e.g.
https://github.com/stm32duino/Arduino_C ... I.cpp#L148

Code: Select all

WEAK void SystemClock_Config(void)
{

  RCC_OscInitTypeDef RCC_OscInitStruct = {};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {};

  /**Configure the main internal regulator output voltage
  */
  __HAL_RCC_PWR_CLK_ENABLE();

  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  /**Initializes the CPU, AHB and APB busses clocks
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 25;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 7;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
    Error_Handler();
  }

  /**Initializes the CPU, AHB and APB busses clocks
  */
  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_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK) {
    Error_Handler();
  }

  /* Ensure CCM RAM clock is enabled */
  __HAL_RCC_CCMDATARAMEN_CLK_ENABLE();

}

system clock and the peripheral clocks are linked, but that if you keep it to the standard published system clocks,
it is tuning the pll multipliers / dividers PLLM, PLLN, PLLP, PLLQ - this is for the stm32f4xx series.
other series may differ.

there is also a python script here, that you can use to explore the PLL configs.
viewtopic.php?t=78

[fpiSTM]

https://github.com/stm32duino/wiki/wiki ... ock_config