STM32F030 使用内部晶振，PF0与PF1作普通IO使用

static void SetSysClock(void)
{
  __IO uint32_t StartUpCounter = 0, HSEStatus = 0;
 
 
     

 //需要修改的关键地方，一定一定。。。。
  //RCC->CR |= ((uint32_t)RCC_CR_HSEON);
 RCC->CR &= ~((uint32_t)RCC_CR_HSEON);

 
  do
  {
    HSEStatus = RCC->CR & RCC_CR_HSERDY;
    StartUpCounter++; 
  } while((HSEStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));

  if ((RCC->CR & RCC_CR_HSERDY) != RESET)
  {
    HSEStatus = (uint32_t)0x01;
  }
  else
  {
    HSEStatus = (uint32_t)0x00;
  } 

  if (HSEStatus == (uint32_t)0x01)
  {
   
    FLASH->ACR = FLASH_ACR_PRFTBE | FLASH_ACR_LATENCY;

   
    RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;
     
   
    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE_DIV1;

   
    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLMULL));
    RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_PREDIV1 | RCC_CFGR_PLLXTPRE_PREDIV1 | RCC_CFGR_PLLMULL6);
           
   
    RCC->CR |= RCC_CR_PLLON;

   
    while((RCC->CR & RCC_CR_PLLRDY) == 0)
    {
    }

   
    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
    RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL;   

   
    while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)RCC_CFGR_SWS_PLL)
    {
    }
  }
  else
  {
  } 
}