stm32f030库里面的函数：

/**
  * @brief  Enables or disables the swap Tx/Rx pins.
  * @param  USARTx: where x can be 1 or 2 to select the USART peripheral.
  * @param  NewState: new state of the USARTx TX/RX pins pinout.
  *          This parameter can be:
  *            @arg ENABLE: The TX and RX pins functions are swapped.
  *            @arg DISABLE: TX/RX pins are used as defined in standard pinout
  * @note   This function has to be called before calling USART_Cmd() function.  
  * @retval None
  */
void USART_SWAPPinCmd(USART_TypeDef* USARTx, FunctionalState NewState)
{
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));
  assert_param(IS_FUNCTIONAL_STATE(NewState));

  if (NewState != DISABLE)
  {
    /* Enable the SWAP feature by setting the SWAP bit in the CR2 register */
    USARTx->CR2 |= USART_CR2_SWAP;
  }
  else
  {
    /* Disable the SWAP feature by clearing the SWAP bit in the CR2 register */
    USARTx->CR2 &= (uint32_t)~((uint32_t)USART_CR2_SWAP);
  }
}