我手头有一片nucelo STM32F411RE 板子,是透过有源振荡器,osc in ,osc out (空接),然后这个振荡器是由 through STLINK MCO pin of STM32F103 microcontroller. The frequencycannot be changed and is fixed at 8 MHz.

         

我找不到这两个宏定义STM32F411xE,#define USE_HSE_BYPASS,这个在那边可以找的到

#if defined(STM32F411xE)    /*!< Uncomment the following line if you need to clock the STM32F411xE by HSE Bypass
     through STLINK MCO pin of STM32F103 microcontroller. The frequency cannot be changed
     and is fixed at 8 MHz.
     Hardware configuration needed for Nucleo Board:
     ?SB54, SB55 OFF
     ?R35 removed
     ?SB16, SB50 ON */
/* #define USE_HSE_BYPASS */     //这叙述为何被屏蔽掉

#if defined(USE_HSE_BYPASS)     
#define HSE_BYPASS_INPUT_FREQUENCY   8000000
#endif /* USE_HSE_BYPASS */   
#endif /* STM32F411xE */