void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    if(huart->Instance == USART2)
    {
        EMPTY_RX++;
        HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_SET);
        HAL_Delay(100);
        HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_RESET);
        HAL_Delay(100);
        if(EMPTY_RX >= BUFF_SIZE)
        {
            EMPTY_RX=0;
        }
        HAL_UART_Receive_IT(&huart2, (uint8_t*)&BUFF_RX[EMPTY_RX], 1);
    }
}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
    if(huart->Instance == USART2)
    {
        uint8_t idx = EMPTY_TX;
        __disable_irq();
        if(BUSY_TX == EMPTY_TX && __HAL_UART_GET_FLAG(&huart2, UART_FLAG_TXE) == SET)
        {
            EMPTY_TX = idx;
            uint8_t tmp = BUFF_TX[BUSY_TX];
            BUSY_TX++;
            if(BUSY_TX >= BUFF_SIZE)
                BUSY_TX = 0;
            HAL_UART_Transmit_IT(&huart2, (uint8_t*)&tmp, 1);
        }
        else
        {
            EMPTY_TX = idx;
        }
        __enable_irq();
    }

}

void send()
{
    uint8_t idx = EMPTY_TX;
    for(int i=0; i<5; i++)
    {
        BUFF_TX[idx] = 0x41;
        idx++;
        if(idx >= BUFF_SIZE)
            idx=0;
    }
}