void USART1_Init (void)
{
    unsigned int integerdivider, tmpreg, fractionaldivider;


    RCC->APB2ENR |= (1u<<2);
  /* Configure PA9 as alternate function push-pull */
    GPIOA->CRH &= ~(1u<<6);
    GPIOA->CRH |=(1u<<4)|(1u<<5)|(1u<<7);        
  /* Configure PA10 as input */
    GPIOA->CRL &= ~((1u<<8)|(1u<<9)|(1u<<11));
    GPIOA->CRL |=(1u<<10);        

  /* Determine the integer part */
  integerdivider = ((0x19 * fclk) / (0x04 * (115200)));
  tmpreg = (integerdivider / 0x64) << 0x04;
  /* Determine the fractional part */
  fractionaldivider = integerdivider - (0x64 * (tmpreg >> 0x04));
  tmpreg |= ((((fractionaldivider * 0x10) + 0x32) / 0x64)) & ((uint8_t)0x0F);
  /* Write to USART BRR */
// USARTx->BRR = (unsigned short)tmpreg;
    
    RCC->APB2ENR |= (1u<<14);
    USART1->BRR = (unsigned short)tmpreg;//313UL; //115200
    USART1->CR1 |= (1UL<<2)|(1UL<<3)|(1UL<<13);
}

void BYTE_Transmit_USART1 (unsigned char data)
{
    USART1->DR = data;
    while (!(USART1->SR & (1UL << 6)));
    USART1->SR &= ~(1UL << 6);    
}

//это передача.
for(i=0; i<10; i++)
{
BYTE_Transmit_USART1(0xAA);
}