小弟初学STM32，串口问题求教

pkzz021 · 发表于 2017-7-19 20:13:35

小弟初学STM32，在学到串口章节的时候，发现一个问题。例程里将uint16_t格式的USART_ReceiveData函数返回值赋给了u8格式的res变量。又将res作为入口参数给了 USART_SendData(USART_TypeDef* USARTx, uint16_t Data)函数，可是此函数的入口参数也是uint16_t格式的，这样不会出现错误吗？

代码已贴在底部，往各位大佬指点。

void USART2_IRQHandler()
{
u8 res;
if(USART_GetITStatus(USART1,USART_IT_RXNE))
{
res=USART_ReceiveData(USART1);
USART_SendData(USART1,res);
}
}

uint16_t USART_ReceiveData(USART_TypeDef* USARTx)
{
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));

  /* Receive Data */
  return (uint16_t)(USARTx->DR & (uint16_t)0x01FF);
}

/**
  * @brief  Transmits break characters.
  * @param  USARTx: Select the USART or the UART peripheral.
  * This parameter can be one of the following values:
  * USART1, USART2, USART3, UART4 or UART5.
  * @retval None
  */
void USART_SendBreak(USART_TypeDef* USARTx)
{
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));

  /* Send break characters */
  USARTx->CR1 |= CR1_SBK_Set;
}

void USART_SendData(USART_TypeDef* USARTx, uint16_t Data)
{
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));
  assert_param(IS_USART_DATA(Data));

  /* Transmit Data */
  USARTx->DR = (Data & (uint16_t)0x01FF);
}

/**
  * @brief  Returns the most recent received data by the USARTx peripheral.
  * @param  USARTx: Select the USART or the UART peripheral.
  * This parameter can be one of the following values:
  * USART1, USART2, USART3, UART4 or UART5.
  * @retval The received data.
  */
uint16_t USART_ReceiveData(USART_TypeDef* USARTx)
{
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));

  /* Receive Data */
  return (uint16_t)(USARTx->DR & (uint16_t)0x01FF);
}