STM32外部晶振和内部晶振切换

在STM32中，可以通过修改寄存器的值来切换外部晶振和内部晶振。以下是一些常用的切换方法：

1. 切换到外部晶振

RCC_OscInitTypeDef RCC_OscInitStruct;

/* Enable HSE Oscillator and activate PLL with HSE as source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON; // HSE启动
RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
HAL_RCC_OscConfig(&RCC_OscInitStruct);

/* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers */
RCC_ClkInitTypeDef RCC_ClkInitStruct;

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_DIV2;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2);

2. 切换到内部晶振

RCC_OscInitTypeDef RCC_OscInitStruct;

/* Enable HSI Oscillator and activate PLL with HSI as source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON; // HSI启动
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
HAL_RCC_OscConfig(&RCC_OscInitStruct);

/* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers */
RCC_ClkInitTypeDef RCC_ClkInitStruct;

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_DIV2;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2);

需要注意的是，切换晶振需要重新配置系统时钟，并且需要根据实际情况调整时钟分频器的值。另外，如果您的程序中使用了外部晶振相关的外设，例如定时器、串口等，需要对代码进行相应的修改，以适应内部晶振。