HAL_UART_Transmit_DMA的标准库版本函数是如何编写

HAL_UART_Transmit_DMA函数是HAL库中UART发送DMA数据的函数，其标准库版本的函数实现如下：

HAL_StatusTypeDef HAL_UART_Transmit_DMA(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size)
{
  HAL_StatusTypeDef status = HAL_OK;

  /* Check that a Tx process is not already ongoing */
  if (huart->gState == HAL_UART_STATE_READY)
  {
    if ((pData == NULL) || (Size == 0U))
    {
      status = HAL_ERROR;
    }
    else
    {
      /* Process Locked */
      __HAL_LOCK(huart);

      huart->pTxBuffPtr = pData;
      huart->TxXferSize = Size;
      huart->TxXferCount = Size;

      /* Computation of UART mask to apply to RDR register */
      UART_MASK_COMPUTATION(huart);

      /* Enable the UART Transmit data register empty Interrupt */
      __HAL_UART_ENABLE_IT(huart, UART_IT_TXE);

      /* Enable the UART DMA requests */
      huart->Instance->CR3 |= USART_CR3_DMAT;

      /* Process Unlocked */
      __HAL_UNLOCK(huart);

      /* Enable the DMA Stream */
      status = HAL_DMA_Start_IT(huart->hdmatx, (uint32_t)pData, (uint32_t)&huart->Instance->TDR, Size);
      if (status == HAL_OK)
      {
        /* Change the UART state */
        huart->gState = HAL_UART_STATE_BUSY_TX;
      }
      else
      {
        /* Disable the DMA transfer for transmit request by resetting the DMAT bit in the UART CR3 register */
        huart->Instance->CR3 &= ~USART_CR3_DMAT;

        /* Process Unlocked */
        __HAL_UNLOCK(huart);

        huart->gState = HAL_UART_STATE_READY;
      }
    }
  }
  else
  {
    status = HAL_BUSY;
  }

  /* Return function status */
  return status;
}

该函数的主要作用是将数据通过DMA方式发送到UART外设上。该函数首先检查是否已经有发送进程正在运行，如果没有，则进一步检查pData和Size参数是否为空。然后，将pData指针和Size大小分别设置为UART_HandleTypeDef结构体中的成员变量pTxBuffPtr和TxXferSize，并将TxXferCount也设置为Size大小。接下来，使能UART的TXE中断和DMA传输请求，并启动DMA传输。最后，将状态设置为HAL_UART_STATE_BUSY_TX，表示发送进程正在运行。如果DMA传输启动失败，则将状态改回HAL_UART_STATE_READY，并返回错误状态HAL_ERROR。如果发送进程正在运行，则返回忙状态HAL_BUSY。