MX串口配置方法见：CubeIDE 利用自带HAL库 串口收发

 

一、代码自动生成以后的项目及代码结构：

main.c中，调用了串口初始化

 

串口初始化函数赋值了串口的参数

 

相当于底层的初始化，配置引脚、并开启中断。

至此串口1配置完毕

二、库文件stm32f1xx_hal_uart.c内的秘密

2.1 初始化

1.usart.c中，MX_USART1_UART_Init 调用了库的HAL_UART_Init，将结构体传递进该函数中

2.HAL_UART_Init干了些什么事？

 if (huart->gState == HAL_UART_STATE_RESET)
  {
    huart->Lock = HAL_UNLOCKED;
    HAL_UART_MspInit(huart);
  }
huart->gState = HAL_UART_STATE_BUSY; 
  __HAL_UART_DISABLE(huart);  /* Disable the peripheral */
  UART_SetConfig(huart);/* Set the UART Communication parameters */

  /* In asynchronous mode, the following bits must be kept cleared:
     - LINEN and CLKEN bits in the USART_CR2 register,
     - SCEN, HDSEL and IREN  bits in the USART_CR3 register.*/
  CLEAR_BIT(huart->Instance->CR2, (USART_CR2_LINEN | USART_CR2_CLKEN));
  CLEAR_BIT(huart->Instance->CR3, (USART_CR3_SCEN | USART_CR3_HDSEL | USART_CR3_IREN));
  __HAL_UART_ENABLE(huart);  /* Enable the peripheral */
  huart->ErrorCode = HAL_UART_ERROR_NONE;
  huart->gState = HAL_UART_STATE_READY;
  huart->RxState = HAL_UART_STATE_READY;

调用MspInit-->修改状态忙-->配置寄存器-->清楚标志位 

2.2 先理解HAL_UART_Receive函数

uint32_t tickstart = 0U;

if (huart->RxState == HAL_UART_STATE_READY)  /* Check that a Rx process is not already ongoing */
  {
    __HAL_LOCK(huart);    /* Process Locked */

    huart->ErrorCode = HAL_UART_ERROR_NONE;
    huart->RxState = HAL_UART_STATE_BUSY_RX;

    tickstart = HAL_GetTick();

    huart->RxXferSize = Size;
    huart->RxXferCount = Size;


    while (huart->RxXferCount > 0U)
    {
      huart->RxXferCount--;
      if (UART_WaitOnFlagUntilTimeout(huart, UART_FLAG_RXNE, RESET, tickstart, Timeout) != HAL_OK)
            return HAL_TIMEOUT;
      *pData++ = (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF);
      }
}

    huart->RxState = HAL_UART_STATE_READY;
    __HAL_UNLOCK(huart);

判断是否忙-->锁住-->标记接收忙-->获取tick计数

-->赋值RxXferCount有多少数据要接收-->每次从DR内获取一个Byte存在pData指向的空间

2.3 HAL_UART_Receive_IT只是配置了一下参数，并没有做任何处理

/* Check that a Rx process is not already ongoing */
  if (huart->RxState == HAL_UART_STATE_READY)
  {
    __HAL_LOCK(huart);    /* Process Locked */
    huart->pRxBuffPtr = pData;
    huart->RxXferSize = Size;
    huart->RxXferCount = Size;
    huart->ErrorCode = HAL_UART_ERROR_NONE;
    huart->RxState = HAL_UART_STATE_BUSY_RX;
    __HAL_UNLOCK(huart);    /* Process Unlocked */

    /*Error Interrupt */
    __HAL_UART_ENABLE_IT(huart, UART_IT_PE);
    __HAL_UART_ENABLE_IT(huart, UART_IT_ERR);

    /* Enable the UART Data Register not empty Interrupt */
    __HAL_UART_ENABLE_IT(huart, UART_IT_RXNE);

    return HAL_OK;
    }

存储在pData指向位置、空间大小RxXferSize 、接收计数RxXferCount ； 接收状态忙；使能接收中断

那么当有数据来的时候，就需要依靠中断函数来处理了。

2.4再看看中断函数在做什么

stm32f1xx_it.c内有定义USART1_IRQHandler，只调用了HAL_UART_IRQHandler函数，下面是

HAL_UART_IRQHandler具体内容

errorflags = (isrflags & (uint32_t)(USART_SR_PE | USART_SR_FE | USART_SR_ORE | USART_SR_NE));
  if (errorflags == RESET)
  {
    if (((isrflags & USART_SR_RXNE) != RESET) && ((cr1its & USART_CR1_RXNEIE) != RESET))
    {
      UART_Receive_IT(huart);
      return;
    }
  }

  /* If some errors occur */
  if ((errorflags != RESET) && (((cr3its & USART_CR3_EIE) != RESET) || ((cr1its & (USART_CR1_RXNEIE | USART_CR1_PEIE)) != RESET)))
  {
//略过错误处理
    /* Call UART Error Call back function if need be --------------------------*/
    if (huart->ErrorCode != HAL_UART_ERROR_NONE)
    {
      /* UART in mode Receiver -----------------------------------------------*/
      if (((isrflags & USART_SR_RXNE) != RESET) && ((cr1its & USART_CR1_RXNEIE) != RESET))
        UART_Receive_IT(huart);
//略过错误处理
        huart->ErrorCode = HAL_UART_ERROR_NONE;
      }
    }
    return;
  } /* End if some error occurs */

  /* UART in mode Transmitter ------------------------------------------------*/
  if (((isrflags & USART_SR_TXE) != RESET) && ((cr1its & USART_CR1_TXEIE) != RESET))
  {    UART_Transmit_IT(huart);    return;  }

  /* UART in mode Transmitter end --------------------------------------------*/
  if (((isrflags & USART_SR_TC) != RESET) && ((cr1its & USART_CR1_TCIE) != RESET))
  {    UART_EndTransmit_IT(huart);    return;  }

无非是三件事，判断是由什么中断响应的，有错误则处理，响应要调用的接收或者发送。

注意区别 UART_Receive_IT 和 HAL_UART_Receive_IT。

HAL_UART_Receive_IT是用户调用的需要接收多少数据存在何处。

UART_Receive_IT是中断调用的有数据收到该如何处理。

2.5 UART_Receive_IT 真正在接收数据的函数，但在最后会关闭中断

  uint16_t *tmp;

  /* Check that a Rx process is ongoing */
  if (huart->RxState == HAL_UART_STATE_BUSY_RX)
  {
    *huart->pRxBuffPtr++ = (uint8_t)(huart->Instance->DR & (uint8_t)0x00FF);
    if (--huart->RxXferCount == 0U)
    {
      __HAL_UART_DISABLE_IT(huart, UART_IT_RXNE);
      __HAL_UART_DISABLE_IT(huart, UART_IT_PE);
      __HAL_UART_DISABLE_IT(huart, UART_IT_ERR);

      huart->RxState = HAL_UART_STATE_READY;

#if (USE_HAL_UART_REGISTER_CALLBACKS == 1)
      /*Call registered Rx complete callback*/
      huart->RxCpltCallback(huart);
#else
      /*Call legacy weak Rx complete callback*/
      HAL_UART_RxCpltCallback(huart);
#endif /* USE_HAL_UART_REGISTER_CALLBACKS */

      return HAL_OK;
    }
    return HAL_OK;
  }

如果是接收状态忙，则从DR中读取1Byte数据。

如果接收计数归零，则使中断失效，并调用回调函数（用户定义则调用用户的，否则调用系统的）

至此，所有用到的代码分析完毕

三、总结

1、HAL_UART_Receive_IT和HAL_UART_Receive的区别就是：中断接收是有数据到了才去读；直接接收是直接读取，如果超时就返回

2、HAL_UART_Receive_IT配置后，有数据来，计数会在调用中断函数之后自动减1。只有到计数为0时，才会关闭中断并调用回调函数。至此有数据来不再调用中断函数，因为中断已经失效。

3、HAL_UART_Receive_IT在计数未至0之前，应该可以读取之前接收到的数据，但这样做应该比较危险。

4、在开源电子的例程中，使用 HAL_UART_Receive_IT(&huart1,(uint8_t *)aRxBuffer, 1);  即Size设置为1，只接收1Byte数据，在每次中断结束后重新配置来使能中断。

四、还有必要再看一眼uart的结构体定义

/**
  * @brief  UART handle Structure definition
  */
typedef struct __UART_HandleTypeDef
{
  USART_TypeDef                 *Instance;        /*!< UART registers base address        */

  UART_InitTypeDef              Init;             /*!< UART communication parameters      */

  uint8_t                       *pTxBuffPtr;      /*!< Pointer to UART Tx transfer Buffer */

  uint16_t                      TxXferSize;       /*!< UART Tx Transfer size              */

  __IO uint16_t                 TxXferCount;      /*!< UART Tx Transfer Counter           */

  uint8_t                       *pRxBuffPtr;      /*!< Pointer to UART Rx transfer Buffer */

  uint16_t                      RxXferSize;       /*!< UART Rx Transfer size              */

  __IO uint16_t                 RxXferCount;      /*!< UART Rx Transfer Counter           */

  DMA_HandleTypeDef             *hdmatx;          /*!< UART Tx DMA Handle parameters      */

  DMA_HandleTypeDef             *hdmarx;          /*!< UART Rx DMA Handle parameters      */

  HAL_LockTypeDef               Lock;             /*!< Locking object                     */

  __IO HAL_UART_StateTypeDef    gState;           /*!< UART state information related to global Handle management
                                                       and also related to Tx operations.
                                                       This parameter can be a value of @ref HAL_UART_StateTypeDef */

  __IO HAL_UART_StateTypeDef    RxState;          /*!< UART state information related to Rx operations.
                                                       This parameter can be a value of @ref HAL_UART_StateTypeDef */

  __IO uint32_t                 ErrorCode;        /*!< UART Error code                    */

#if (USE_HAL_UART_REGISTER_CALLBACKS == 1)
  void (* TxHalfCpltCallback)(struct __UART_HandleTypeDef *huart);        /*!< UART Tx Half Complete Callback        */
  void (* TxCpltCallback)(struct __UART_HandleTypeDef *huart);            /*!< UART Tx Complete Callback             */
  void (* RxHalfCpltCallback)(struct __UART_HandleTypeDef *huart);        /*!< UART Rx Half Complete Callback        */
  void (* RxCpltCallback)(struct __UART_HandleTypeDef *huart);            /*!< UART Rx Complete Callback             */
  void (* ErrorCallback)(struct __UART_HandleTypeDef *huart);             /*!< UART Error Callback                   */
  void (* AbortCpltCallback)(struct __UART_HandleTypeDef *huart);         /*!< UART Abort Complete Callback          */
  void (* AbortTransmitCpltCallback)(struct __UART_HandleTypeDef *huart); /*!< UART Abort Transmit Complete Callback */
  void (* AbortReceiveCpltCallback)(struct __UART_HandleTypeDef *huart);  /*!< UART Abort Receive Complete Callback  */
  void (* WakeupCallback)(struct __UART_HandleTypeDef *huart);            /*!< UART Wakeup Callback                  */

  void (* MspInitCallback)(struct __UART_HandleTypeDef *huart);           /*!< UART Msp Init callback                */
  void (* MspDeInitCallback)(struct __UART_HandleTypeDef *huart);         /*!< UART Msp DeInit callback              */
#endif  /* USE_HAL_UART_REGISTER_CALLBACKS */

} UART_HandleTypeDef;