STM32串口中USART_GetITStatus与USART_GetFlagStatus的区别是什么？

一、ITStatus USART_GetITStatus(USART_TypeDef* USARTx, uint16_t USART_IT)在判断相应位是否置1（读SR寄存器）前会先判断相应位的中断是否使能（读CR寄存器）。


所以若使用 while(USART_GetITStatus(USART1,USART_IT_TC) != SET); 来进行判断数据是否发送完成，


注意需使能TC中断 USART_ITConfig(USART1, USART_IT_TC, ENABLE);  否则会一直返回0导致死在while里。


/**
  * @brief  Checks whether the specified USART interrupt has occurred or not.
  * @param  USARTx: Select the USART or the UART peripheral.
  *   This parameter can be one of the following values:
  *   USART1, USART2, USART3, UART4 or UART5.
  * @param  USART_IT: specifies the USART interrupt source to check.
  *   This parameter can be one of the following values:
  *     @arg USART_IT_CTS:  CTS change interrupt (not available for UART4 and UART5)
  *     @arg USART_IT_LBD:  LIN Break detection interrupt
  *     @arg USART_IT_TXE:  Tansmit Data Register empty interrupt
  *     @arg USART_IT_TC:   Transmission complete interrupt
  *     @arg USART_IT_RXNE: Receive Data register not empty interrupt
  *     @arg USART_IT_IDLE: Idle line detection interrupt
  *     @arg USART_IT_ORE:  OverRun Error interrupt
  *     @arg USART_IT_NE:   Noise Error interrupt
  *     @arg USART_IT_FE:   Framing Error interrupt
  *     @arg USART_IT_PE:   Parity Error interrupt
  * @retval The new state of USART_IT (SET or RESET).
  */
ITStatus USART_GetITStatus(USART_TypeDef* USARTx, uint16_t USART_IT)
{
  uint32_t bitpos = 0x00, itmask = 0x00, usartreg = 0x00;
  ITStatus bitstatus = RESET;
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));
  assert_param(IS_USART_GET_IT(USART_IT));
  /* The CTS interrupt is not available for UART4 and UART5 */
  if (USART_IT == USART_IT_CTS)
  {
    assert_param(IS_USART_123_PERIPH(USARTx));
  }   
  
  /* Get the USART register index */
  usartreg = (((uint8_t)USART_IT) >> 0x05);
  /* Get the interrupt position */
  itmask = USART_IT & IT_Mask;
  itmask = (uint32_t)0x01 << itmask;
  
  if (usartreg == 0x01) /* The IT  is in CR1 register */
  {
    itmask &= USARTx->CR1;
  }
  else if (usartreg == 0x02) /* The IT  is in CR2 register */
  {
    itmask &= USARTx->CR2;
  }
  else /* The IT  is in CR3 register */
  {
    itmask &= USARTx->CR3;
  }
  
  bitpos = USART_IT >> 0x08;
  bitpos = (uint32_t)0x01 << bitpos;
  bitpos &= USARTx->SR;
  if ((itmask != (uint16_t)RESET)&&(bitpos != (uint16_t)RESET))
  {
    bitstatus = SET;
  }
  else
  {
    bitstatus = RESET;
  }
  
  return bitstatus;  
}


二、FlagStatus USART_GetFlagStatus(USART_TypeDef* USARTx, uint16_t USART_FLAG)直接判断相应位是否置1（读SR寄存器），而不会判断相应中断是否开启，通常可用于没开启相应中断时进行判断，比如只使用了串口接收到数据进入中断时，只需使能 USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); 无需再使能多余的中断。


void USART1_IRQHandler(void)
{
        u8 res;
        if(USART_GetITStatus(USART1,USART_IT_RXNE) != RESET)//Receive Data register not empty interrupt
        {
                res = USART_ReceiveData(USART1);
                while(USART_GetFlagStatus(USART1,USART_FLAG_TXE) != SET);//判断发送缓冲区是否空
                USART_SendData(USART1,res);
                while(USART_GetFlagStatus(USART1,USART_FLAG_TC) != SET);
                //while(USART_GetITStatus(USART1,USART_IT_TC) != SET);//需使能TC中断
        }
        USART_ClearFlag(USART1,USART_FLAG_TC);
        //USART_ClearITPendingBit(USART1,USART_IT_TC); //与USART_ClearFlag同种效果
}
/**
  * @brief  Checks whether the specified USART flag is set or not.
  * @param  USARTx: Select the USART or the UART peripheral.
  *   This parameter can be one of the following values:
  *   USART1, USART2, USART3, UART4 or UART5.
  * @param  USART_FLAG: specifies the flag to check.
  *   This parameter can be one of the following values:
  *     @arg USART_FLAG_CTS:  CTS Change flag (not available for UART4 and UART5)
  *     @arg USART_FLAG_LBD:  LIN Break detection flag
  *     @arg USART_FLAG_TXE:  Transmit data register empty flag
  *     @arg USART_FLAG_TC:   Transmission Complete flag
  *     @arg USART_FLAG_RXNE: Receive data register not empty flag
  *     @arg USART_FLAG_IDLE: Idle Line detection flag
  *     @arg USART_FLAG_ORE:  OverRun Error flag
  *     @arg USART_FLAG_NE:   Noise Error flag
  *     @arg USART_FLAG_FE:   Framing Error flag
  *     @arg USART_FLAG_PE:   Parity Error flag
  * @retval The new state of USART_FLAG (SET or RESET).
  */
FlagStatus USART_GetFlagStatus(USART_TypeDef* USARTx, uint16_t USART_FLAG)
{
  FlagStatus bitstatus = RESET;
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));
  assert_param(IS_USART_FLAG(USART_FLAG));
  /* The CTS flag is not available for UART4 and UART5 */
  if (USART_FLAG == USART_FLAG_CTS)
  {
    assert_param(IS_USART_123_PERIPH(USARTx));
  }  
  
  if ((USARTx->SR & USART_FLAG) != (uint16_t)RESET)
  {
    bitstatus = SET;
  }
  else
  {
    bitstatus = RESET;
  }
  return bitstatus;
}


总结：我认为在GetITStatus和GetFlagStatus不仅在串口中是这种区别，在其他地方比如外部中断中使用也是类似道理。