001 时钟RCC

RCC（Reset Clock Control）

/**
  * @brief  System Clock Configuration
  *         The system Clock is configured as follow : 
  *            System Clock source            = PLL (HSE)
  *            SYSCLK(Hz)                     = 72000000
  *            HCLK(Hz)                       = 72000000
  *            AHB Prescaler                  = 1
  *            APB1 Prescaler                 = 2
  *            APB2 Prescaler                 = 1
  *            HSE Frequency(Hz)              = 8000000
  *            HSE PREDIV1                    = 2
  *            PLLMUL                         = 9
  *            Flash Latency(WS)              = 0
  * @param  None
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_ClkInitTypeDef clkinitstruct = {0};
  RCC_OscInitTypeDef oscinitstruct = {0};
  
  /* Enable HSE Oscillator and activate PLL with HSE as source */
  oscinitstruct.OscillatorType  = RCC_OSCILLATORTYPE_HSE;
  oscinitstruct.HSEState        = RCC_HSE_ON;
  // RCC_HSE_PREDIV_DIV1 = 0
  oscinitstruct.HSEPredivValue  = RCC_HSE_PREDIV_DIV1;
  oscinitstruct.PLL.PLLState    = RCC_PLL_ON;
  oscinitstruct.PLL.PLLSource   = RCC_PLLSOURCE_HSE;
  // 8MHz * 9 = 72MHz
  oscinitstruct.PLL.PLLMUL      = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&oscinitstruct)!= HAL_OK)
  {
    /* Initialization Error */
    while(1); 
  }

  /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 
     clocks dividers */
  clkinitstruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
  // SYSCLK=72Mhz
  clkinitstruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  // AHB, HCLK=72Mhz
  clkinitstruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  // APB2, HCLK=72Mhz
  clkinitstruct.APB2CLKDivider = RCC_HCLK_DIV1;
  // APB1, HCLK=36Mhz
  clkinitstruct.APB1CLKDivider = RCC_HCLK_DIV2;  
  if (HAL_RCC_ClockConfig(&clkinitstruct, FLASH_LATENCY_2)!= HAL_OK)
  {
    /* Initialization Error */
    while(1); 
  }
}