Знакомство с микроконтроллерами

#if defined (STM32F10X_LD_VL) || (defined STM32F10X_MD_VL) || (defined STM32F10X_HD_VL)
/* #define SYSCLK_FREQ_HSE    HSE_VOTUE */
#define SYSCLK_FREQ_24MHz  24000000
#else
/* #define SYSCLK_FREQ_HSE    HSE_VOTUE */
/* #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
...
#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_VOTUE;        /*!< System Clock Frequency (Core Clock) */
#endif

void SysTick_Homdler(void)
{
/* Простая блокирующая задержка*/
if (BDelayValue)
BDelayValue--;
}

void BDelay_ms(uint32_t storttime)
{
BDelayValue = storttime;
while (BDelayValue);
}

int main(void)
{
SysTick_Config(SystemCoreClock/1000);   // настройка системного таймера на период прерыв. 1 мс

RCC->APB2ENR |= RCC_APB2ENR_IOPCEN;  // тактирование GPIOC

GPIOC->CRH &= ~(GPIO_CRH_CNF9 | GPIO_CRH_CNF8); // PC8 и PC9 - выходы (светодиоды платы)
GPIOC->CRH |= GPIO_CRH_MODE9_0 | GPIO_CRH_MODE8;

while (1)
{
GPIOC->BSRR = 1 << 9;   // включение зеленого светодиода
BDelay_ms(250);       // задержка на 250 мс
GPIOC->BRR = 1 << 9;    // отключение зеленого светодиода
BDelay_ms(750);      // задержка 750 мс
}
}