本帖最后由 世上最美丽的裤头 于 2017-4-13 11:24 编辑

使用的是stm32f103 V1.40版本的库UART DMA发送的问题发送函数
HAL_StatusTypeDef HAL_UART_Transmit_DMA(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size);
发送完毕之后成功的回调函数也正常，可是再次发送的时候就发不出去了。一直返回错误。
我们看下这个函数的代码
[mw_shl_code=applescript,true]HAL_StatusTypeDef HAL_UART_Transmit_DMA(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size)
{
  uint32_t *tmp;
  uint32_t tmp_state = 0;

  tmp_state = huart->State;
  if((tmp_state == HAL_UART_STATE_READY) || (tmp_state == HAL_UART_STATE_BUSY_RX))
  {
    if((pData == NULL ) || (Size == 0))
    {
      return HAL_ERROR;
    }

    /* Process Locked */
    __HAL_LOCK(huart);

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

    huart->ErrorCode = HAL_UART_ERROR_NONE;
    /* Check if a receive process is ongoing or not */
    if(huart->State == HAL_UART_STATE_BUSY_RX)
    {
      huart->State = HAL_UART_STATE_BUSY_TX_RX;
    }
    else
    {
      huart->State = 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;

    /* Enable the UART transmit DMA channel */
    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);

    /* 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);

    /* Process Unlocked */
    __HAL_UNLOCK(huart);

    return HAL_OK;
  }
  else
  {
    return HAL_BUSY;
  }
}[/mw_shl_code]代码中可以看出，发送之前先判断状态标志，不是在发送状态才进行发送，这也正常。但是，发送一次之后，状态就被至为发送状态，发送完毕也没有清楚，这就导致了下次再发送，判断为忙，就发不出去了。我们看下他发送成功的处理部分。[mw_shl_code=applescript,true]static void UART_DMATransmitCplt(DMA_HandleTypeDef *hdma)     
{
  UART_HandleTypeDef* huart = ( UART_HandleTypeDef* )((DMA_HandleTypeDef* )hdma)->Parent;
  /* DMA Normal mode*/
  if ( HAL_IS_BIT_CLR(hdma->Instance->CCR, DMA_CCR_CIRC) )
  {
    huart->TxXferCount = 0;

    /* Disable the DMA transfer for transmit request by setting the DMAT bit
       in the UART CR3 register */
    CLEAR_BIT(huart->Instance->CR3, USART_CR3_DMAT);

    /* Enable the UART Transmit Complete Interrupt */   
    __HAL_UART_ENABLE_IT(huart, UART_IT_TC);
  }
  /* DMA Circular mode */
  else
  {
    HAL_UART_TxCpltCallback(huart);
  }[/mw_shl_code]代码中可以看到，并没有清除发送的状态，这就导致了下次发送不成功的问题。
难道要自己发送之前清除一下状态，我想这应该不是库函数的本意。
我们对比看下接收成功是如何处理的[mw_shl_code=applescript,true]static void UART_DMAReceiveCplt(DMA_HandleTypeDef *hdma)  
{
  UART_HandleTypeDef* huart = ( UART_HandleTypeDef* )((DMA_HandleTypeDef* )hdma)->Parent;
  /* DMA Normal mode*/
  if ( HAL_IS_BIT_CLR(hdma->Instance->CCR, DMA_CCR_CIRC) )
  {
    huart->RxXferCount = 0;

    /* Disable the DMA transfer for the receiver request by setting the DMAR bit
       in the UART CR3 register */
    CLEAR_BIT(huart->Instance->CR3, USART_CR3_DMAR);

    /* Check if a transmit process is ongoing or not */
    if(huart->State == HAL_UART_STATE_BUSY_TX_RX)
    {
      huart->State = HAL_UART_STATE_BUSY_TX;
    }
    else
    {
      huart->State = HAL_UART_STATE_READY;
    }
  }
  HAL_UART_RxCpltCallback(huart);
}[/mw_shl_code]接收成功之后有正确清除状态标志，发送成功应该也是同样的，所以可能是漏掉了。我们加上即可[mw_shl_code=applescript,true]static void UART_DMATransmitCplt(DMA_HandleTypeDef *hdma)     
{
  UART_HandleTypeDef* huart = ( UART_HandleTypeDef* )((DMA_HandleTypeDef* )hdma)->Parent;
  /* DMA Normal mode*/
  if ( HAL_IS_BIT_CLR(hdma->Instance->CCR, DMA_CCR_CIRC) )
  {
    huart->TxXferCount = 0;

    /* Disable the DMA transfer for transmit request by setting the DMAT bit
       in the UART CR3 register */
    CLEAR_BIT(huart->Instance->CR3, USART_CR3_DMAT);

    /* Enable the UART Transmit Complete Interrupt */   
    __HAL_UART_ENABLE_IT(huart, UART_IT_TC);

      /* Check if a transmit process is ongoing or not */
    if(huart->State == HAL_UART_STATE_BUSY_TX_RX) //这里是增加的代码
    {
      huart->State = HAL_UART_STATE_BUSY_RX;
    }
    else
    {
      huart->State = HAL_UART_STATE_READY;
    }
  }
  /* DMA Circular mode */
  else     //普通模式没有回调发送成功，注释掉次else则修改为发送完成回调
  {
    HAL_UART_TxCpltCallback(huart);
  }
}[/mw_shl_code]

测试，可以正常发送了····