stm32 HAL库 HAL_UART_Transmit_DMA 发送函数分析
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stm32 HAL库 HAL_UART_Transmit_DMA 发送函数分析
vccw 发表于1年前
stm32 HAL库 HAL_UART_Transmit_DMA 发送函数分析
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摘要: stm32cube HAL Transmit_DMA

请勿转载。谢谢。

###1.函数主体内容

HAL_StatusTypeDef HAL_UART_Transmit_DMA(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size)
{
  uint32_t *tmp;
  
  /* Check that a Tx process is not already ongoing */
  if(huart->gState == HAL_UART_STATE_READY)
  {
    if((pData == NULL ) || (Size == 0U))
    {
      return HAL_ERROR;
    }

    /* Process Locked */
    __HAL_LOCK(huart);

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

    huart->ErrorCode = HAL_UART_ERROR_NONE;
    huart->gState = HAL_UART_STATE_BUSY_TX;

    /* Set the UART DMA transfer complete callback */
    huart->hdmatx->XferCpltCallback = UART_DMATransmitCplt;

    /* Set the UART DMA Half transfer complete callback */
    huart->hdmatx->XferHalfCpltCallback = UART_DMATxHalfCplt;

    /* Set the DMA error callback */
    huart->hdmatx->XferErrorCallback = UART_DMAError;

    /* Set the DMA abort callback */
    huart->hdmatx->XferAbortCallback = NULL;

    /* Enable the UART transmit DMA Stream */
    tmp = (uint32_t*)&pData;
    HAL_DMA_Start_IT(huart->hdmatx, *(uint32_t*)tmp, (uint32_t)&huart->Instance->DR, Size);
    
    /* Clear the TC flag in the SR register by writing 0 to it */
    __HAL_UART_CLEAR_FLAG(huart, UART_FLAG_TC);
    
    /* Process Unlocked */
    __HAL_UNLOCK(huart);
    
    /* Enable the DMA transfer for transmit request by setting the DMAT bit
       in the UART CR3 register */
    SET_BIT(huart->Instance->CR3, USART_CR3_DMAT);
    
    return HAL_OK;
  }
  else
  {
    return HAL_BUSY;
  }
}

如上就是HAL_UART_Transmit_DMA 函数全部的代码。除去些初始化的代码,可以提炼到比较重要的代码如下

设置memory 到 periphery 的地址,并且开启中断 并使能DMA通道

HAL_DMA_Start_IT(huart->hdmatx, *(uint32_t*)tmp, (uint32_t)&huart->Instance->DR, Size);

清除串口 TC 中断 FLAG

__HAL_UART_CLEAR_FLAG(huart, UART_FLAG_TC);

使能发送

SET_BIT(huart->Instance->CR3, USART_CR3_DMAT);

2.调用HAL_DMA_Start_IT

设置memory 到 periphery 的地址,并且开启中断 并使能DMA通道 函数内容如下

HAL_StatusTypeDef HAL_DMA_Start_IT(DMA_HandleTypeDef *hdma, uint32_t SrcAddress, uint32_t DstAddress, uint32_t DataLength)
{
  HAL_StatusTypeDef status = HAL_OK;

  /* calculate DMA base and stream number */
  DMA_Base_Registers *regs = (DMA_Base_Registers *)hdma->StreamBaseAddress;
  
  /* Check the parameters */
  assert_param(IS_DMA_BUFFER_SIZE(DataLength));
 
  /* Process locked */
  __HAL_LOCK(hdma);
  
  if(HAL_DMA_STATE_READY == hdma->State)
  {
    /* Change DMA peripheral state */
    hdma->State = HAL_DMA_STATE_BUSY;
    
    /* Initialize the error code */
    hdma->ErrorCode = HAL_DMA_ERROR_NONE;
    
    /* Configure the source, destination address and the data length */
    DMA_SetConfig(hdma, SrcAddress, DstAddress, DataLength);
    
    /* Clear all interrupt flags at correct offset within the register */
    regs->IFCR = 0x3FU << hdma->StreamIndex;
    
    /* Enable Common interrupts*/
    hdma->Instance->CR  |= DMA_IT_TC | DMA_IT_TE | DMA_IT_DME;
    hdma->Instance->FCR |= DMA_IT_FE;
    
    if(hdma->XferHalfCpltCallback != NULL)
    {
      hdma->Instance->CR  |= DMA_IT_HT;
    }
    
    /* Enable the Peripheral */

__HAL_DMA_ENABLE(hdma);

  }
  else
  {
    /* Process unlocked */
    __HAL_UNLOCK(hdma);	  
    
    /* Return error status */
    status = HAL_BUSY;
  }
  
  return status;
}

设置memory 到 periphery 地址

DMA_SetConfig(hdma, SrcAddress, DstAddress, DataLength);

打开中断

    hdma->Instance->CR  |= DMA_IT_TC | DMA_IT_TE | DMA_IT_DME;
    hdma->Instance->FCR |= DMA_IT_FE;

开启通道

__HAL_DMA_ENABLE(hdma);

关于开启通道的的这个marco 可以在这条语句中得到解答

#define __HAL_DMA_ENABLE(__HANDLE__)      ((__HANDLE__)->Instance->CR |=  DMA_SxCR_EN)

###3.结尾 那么HAL_UART_Transmit_DMA 函数主要做的事情顺序如下

  • 设置memory 到 periphery 的地址,并且开启中断 并使能DMA通道
  • 清除串口 TC 中断 FLAG
  • 使能发送
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