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);
}

    /* для устройств на шине APB2 (up to 72 MHz) */
    static uint_fast32_t
    calcdivround_apb2(
        int_fast32_t freq        /* требуемая частота на выходе делителя, в герцах. */
        )
    {
        return (APB2_FREQ + freq / 2) / freq;
    }

    USART1->BRR = calcdivround_apb2(baudrate);        // младшие 4 бита - это дробная часть.

    RCC->APB2ENR |= RCC_APB2ENR_USART1EN; // Включение тактирования USART1.


    USART1->CR1 |= (USART_CR1_RE | USART_CR1_TE); // Transmitter Enable & Receiver Enables


    RCC->APB2ENR |= RCC_APB2ENR_AFIOEN;     //включить тактирование альтернативных функций

    arm_hardware_pioa_periphout_altfn2(GPIO_ODR_ODR9, 255);    // TX DATA line (2 MHz)
    arm_hardware_pioa_inputs(GPIO_ODR_ODR10);        // RX data line

    NVIC_EnableIRQ(USART1_IRQn);        // enable USART1_IRQHandler();

    USART1->CR1 |= USART_CR1_UE; // Включение USART1.

RCC_GetClocksFreq(&RCC_ClocksStatus);
  if ((*(u32*)&USARTx) == USART1_BASE)
  {
    apbclock = RCC_ClocksStatus.PCLK2_Frequency;
  }
  else
  {
    apbclock = RCC_ClocksStatus.PCLK1_Frequency;
  }

  /* Determine the integer part */
  integerdivider = ((0x19 * apbclock) / (0x04 * (USART_InitStruct->USART_BaudRate)));
  tmpreg = (integerdivider / 0x64) << 0x04;

  /* Determine the fractional part */
  fractionaldivider = integerdivider - (0x64 * (tmpreg >> 0x04));
  tmpreg |= ((((fractionaldivider * 0x10) + 0x32) / 0x64)) & ((u8)0x0F);

  /* Write to USART BRR */
  USARTx->BRR = (u16)tmpreg;

    USART1->BRR = (PCLK1_FREQ + TERMINAL_BAUDRATE / 2) / TERMINAL_BAUDRATE;

            for(i=0; i<10; i++)
                {
                    BYTE_Transmit_USART1(0xAA);
                }

            for(i=0; i<1000000; i++)
                {

                }

RCC->APB2ENR |= RCC_APB2ENR_AFIOEN;

RCC->APB2ENR |= (1u<<14)

RCC->APB2ENR |= RCC_APB2ENR_USART1EN

  /* Configure PA10 as input */
    GPIOA->CRL &= ~((1u<<8)|(1u<<9)|(1u<<11));
    GPIOA->CRL |=(1u<<10);

arm_hardware_pioa_periphout_altfn2(GPIO_ODR_ODR9, 255);    // TX DATA line (2 MHz)
    arm_hardware_pioa_inputs(GPIO_ODR_ODR10);        // RX data line

    RCC->APB2ENR |= (1u<<0);//AFIOEN: Alternate function I/O clock enable
    RCC->APB2ENR |= (1u<<2);//IOPAEN: I/O port A clock enable
    RCC->APB2ENR |= (1u<<14);//USART1EN: USART1 clock enable

    USART1->BRR = (72000000UL + 115200UL / 2UL) / 115200UL;
    USART1->SR &= ~(1UL << 6);    
    USART1->CR1 |= (1UL<<13);
    USART1->CR1 |= (1UL<<2)|(1UL<<3);//    
    
  /* Configure PA9 as alternate function push-pull */
    GPIOA->CRH &= ~((1u<<4)|(1u<<6));
    GPIOA->CRH |=(1u<<5)|(1u<<7);        
  /* Configure PA10 as input */
    GPIOA->CRH &= ~((1u<<8)|(1u<<9)|(1u<<11));
    GPIOA->CRH |=(1u<<10);            
}

void BYTE_Transmit_USART1 (unsigned char data)
{
    USART1->DR = 0xAA;//data;
    while (!(USART1->SR & (1UL << 6)));
}