1、首先对楼主的一些建议：想要外设测试样例，不要去网上找，网上的根本没保证，就简单最可靠的就是去STM32CubeMX库里面找每个系列都对应的官方开发板，都有外设的驱动样例。以STM32L476RG-Nucleo为例，打开里面有很多代码可以学习参考： 各种外设驱动样例： 2、其次，楼主只贴了RCC代码，无法明确问题原因，只能帮楼主分析下，如果使用完整的HAL驱动的话，串口初始化，会执行底层的HAL_StatusTypeDef UART_SetConfig(UART_HandleTypeDef *huart)函数，里面会获取UART时钟源，并根据时钟源去查找系统当前时钟，进而进行波特率等更时钟相关的寄存器设置，而程序是如何知道系统当前时钟的呢？答案是stm32l4xx_hal_conf.h中定义的，并不是神奇的软件能够自动识别硬件得到的，只是根据RCC寄存器值获取分频、倍频等参数状态+基础时钟（HSE\HSI\LSE\LSI等）计算出来的，关键的就在这些定义上，如： /* ########################## Oscillator Values adaptation ####################*/ /** * @brief Adjust the value of External High Speed oscillator (HSE) used in your application. * This value is used by the RCC HAL module to compute the system frequency * (when HSE is used as system clock source, directly or through the PLL). */ #if !defined (HSE_VALUE) #define HSE_VALUE ((uint32_t)8000000) /*!< Value of the External oscillator in Hz */ #endif /* HSE_VALUE */ #if !defined (HSE_STARTUP_TIMEOUT) #define HSE_STARTUP_TIMEOUT ((uint32_t)100) /*!< Time out for HSE start up, in ms */ #endif /* HSE_STARTUP_TIMEOUT */ /** * @brief Internal Multiple Speed oscillator (MSI) default value. * This value is the default MSI range value after Reset. */ #if !defined (MSI_VALUE) #define MSI_VALUE ((uint32_t)4000000) /*!< Value of the Internal oscillator in Hz*/ #endif /* MSI_VALUE */ /** * @brief Internal High Speed oscillator (HSI) value. * This value is used by the RCC HAL module to compute the system frequency * (when HSI is used as system clock source, directly or through the PLL). */ #if !defined (HSI_VALUE) #define HSI_VALUE ((uint32_t)16000000) /*!< Value of the Internal oscillator in Hz*/ #endif /* HSI_VALUE */ /** * @brief Internal Low Speed oscillator (LSI) value. */ #if !defined (LSI_VALUE) #define LSI_VALUE ((uint32_t)32000) /*!< LSI Typical Value in Hz*/ #endif /* LSI_VALUE */ /*!< Value of the Internal Low Speed oscillator in Hz The real value may vary depending on the variations in voltage and temperature.*/ /** * @brief External Low Speed oscillator (LSE) value. * This value is used by the UART, RTC HAL module to compute the system frequency */ #if !defined (LSE_VALUE) #define LSE_VALUE ((uint32_t)32768) /*!< Value of the External oscillator in Hz*/ #endif /* LSE_VALUE */ #if !defined (LSE_STARTUP_TIMEOUT) #define LSE_STARTUP_TIMEOUT ((uint32_t)5000) /*!< Time out for LSE start up, in ms */ #endif /* HSE_STARTUP_TIMEOUT */ /** * @brief External clock source for SAI1 peripheral * This value is used by the RCC HAL module to compute the SAI1 & SAI2 clock source * frequency. */ #if !defined (EXTERNAL_SAI1_CLOCK_VALUE) #define EXTERNAL_SAI1_CLOCK_VALUE ((uint32_t)48000) /*!< Value of the SAI1 External clock source in Hz*/ #endif /* EXTERNAL_SAI1_CLOCK_VALUE */ /** * @brief External clock source for SAI2 peripheral * This value is used by the RCC HAL module to compute the SAI1 & SAI2 clock source * frequency. */ #if !defined (EXTERNAL_SAI2_CLOCK_VALUE) #define EXTERNAL_SAI2_CLOCK_VALUE ((uint32_t)48000) /*!< Value of the SAI2 External clock source in Hz*/ #endif /* EXTERNAL_SAI2_CLOCK_VALUE */ 复制代码比如如果你使用外部8M高速晶振，你需要修改HSE_VALUE为8000000，假设你实际使用的外部晶振为12M，而你的HSE_VALUE仍为8000000，系统也会跑起来，但是通过HAL_RCC_GetSysClockFreq()等获取时钟的函数得到的值就不对了。也许这就是问题原因的所在，希望楼主能解决此问题。
因为你把那个去掉了.这里屏蔽了.即使不定义,这里判断走的是else分支. //#ifdef STM32F10X_CL // #define HSE_VALUE ((uint32_t)25000000) /*!< Value of the External oscillator in Hz */ //#else #define HSE_VALUE ((uint32_t)8000000) /*!< Value of the External oscillator in Hz */ //#endif /* STM32F10X_CL */ #endif /* HSE_VALUE */
