Posted on September 27, 2017 at 10:36
Hi,
Thanks for reply. Actually I meant to say that the initialization of “SystemCoreClock�? is wrong.
In the era of SPL(standard package library, which I still prefer in some aspects mainly for its comprehensive examples ) the initialization of system clock was the duty of “SystemInit()�? function which is defined in “system_stm32xxxx.c�? and called at startup before coming to main function(for example line 150 in startup_stm32f10x_hd.s). So, At the entry of main function system clock was truly initialized base on one of the following defines in “system_stm32xxxx.c�?:
#if defined (STM32F10X_LD_VL) || (defined STM32F10X_MD_VL) || (defined STM32F10X_HD_VL)
/* #define SYSCLK_FREQ_HSE HSE_VALUE */
#define SYSCLK_FREQ_24MHz 24000000
#else
/* #define SYSCLK_FREQ_HSE HSE_VALUE */
/* #define SYSCLK_FREQ_24MHz 24000000 */
/* #define SYSCLK_FREQ_36MHz 36000000 */
/* #define SYSCLK_FREQ_48MHz 48000000 */
/* #define SYSCLK_FREQ_56MHz 56000000 */
#define SYSCLK_FREQ_72MHz 72000000
#endif
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and then:
#ifdef SYSCLK_FREQ_HSE
uint32_t SystemCoreClock = SYSCLK_FREQ_HSE; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_24MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_24MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_36MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_36MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_48MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_48MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_56MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_56MHz; /*!< System Clock Frequency (Core Clock) */
#elif defined SYSCLK_FREQ_72MHz
uint32_t SystemCoreClock = SYSCLK_FREQ_72MHz; /*!< System Clock Frequency (Core Clock) */
#else /*!< HSI Selected as System Clock source */
uint32_t SystemCoreClock = HSI_VALUE; /*!< System Clock Frequency (Core Clock) */
#endif
�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?
While in new version of “system_stm32xxxx.c�? (one which is used in CubeMX) the above
definitions are truncated to :
#if defined(STM32F100xB) ||defined(STM32F100xE)
uint32_t SystemCoreClock = 24000000; /*!< System Clock Frequency (Core Clock) */
#else /*!< HSI Selected as System Clock source */
uint32_t SystemCoreClock = 72000000; /*!< System Clock Frequency (Core Clock) */
#endif
�?�?�?�?�?
As a result at startup that system clock is HSI (8 MHz) and no setting is done inside “SystemInit()�? (absence of “SetSysClock()�? function) the clock is wrongly assumed as 72MHz.
