STM32学习笔记

• 时钟配置

时钟配置

• 时钟树
  

• 系统时钟倍频到168MHz

 void SystemClock_Config(void)
{
  RCC_ClkInitTypeDef RCC_ClkInitStruct;
  RCC_OscInitTypeDef RCC_OscInitStruct;
  
  /* Enable Power Control clock */
  __HAL_RCC_PWR_CLK_ENABLE();
  
  /* The voltage scaling allows optimizing the power consumption when the device is 
     clocked below the maximum system frequency, to update the voltage scaling value 
     regarding system frequency refer to product datasheet.  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  /* Enable HSE Oscillator and activate PLL with HSE as source */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 8;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 7;
  HAL_RCC_OscConfig(&RCC_OscInitStruct);
  
  /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 
     clocks dividers */
  RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | 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;  
  HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5);

  /* STM32F405x/407x/415x/417x Revision Z devices: prefetch is supported  */
  if (HAL_GetREVID() == 0x1001)
  {
    /* Enable the Flash prefetch */
    __HAL_FLASH_PREFETCH_BUFFER_ENABLE();
  }
}

• 注意：HSE默认频率为25MHz,在 stm32f4xx_hal_conf.h 中按照实际情况修改外部高速晶振频率值 HSE_VALUE
  

• 验证时钟频率

  • 输出系统频率到MCO脚
  • 调用函数获取时钟频率值

// Debug 仿真 wathch 只能查看全局变量
uint32_t SySCLKFreq = 0;
uint32_t HCLKFreq = 0;
uint32_t PCLK1Freq = 0;
uint32_t PCLK2Freq = 0;

int main(void){	
	
	HAL_Init();

	SystemClock_Config();
	
	HAL_RCC_MCOConfig(RCC_MCO2,RCC_MCO2SOURCE_SYSCLK,RCC_MCODIV_1);
	SystemCoreClockUpdate();
	
	SySCLKFreq = HAL_RCC_GetSysClockFreq();
	HCLKFreq = HAL_RCC_GetHCLKFreq();
	PCLK1Freq = HAL_RCC_GetPCLK1Freq();
	PCLK2Freq = HAL_RCC_GetPCLK2Freq();
}