使用DMA通道要注意的两个地方

eric2013

特别注意标红的地方。实际测试不加也没事的，不过为了稳定起见还是加上。
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static void DMA_Config(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;
  DMA_InitTypeDef  DMA_InitStructure;
  __IO uint32_t    Timeout = TIMEOUT_MAX;
   
  /* Enable DMA clock */
  RCC_AHB1PeriphClockCmd(DMA_STREAM_CLOCK, ENABLE);
  
  /* Reset DMA Stream registers (for debug purpose) */
  DMA_DeInit(DMA_STREAM);


  /* Check if the DMA Stream is disabled before enabling it.
     Note that this step is useful when the same Stream is used multiple times:
     enabled, then disabled then re-enabled... In this case, the DMA Stream disable
     will be effective only at the end of the ongoing data transfer and it will
     not be possible to re-configure it before making sure that the Enable bit
     has been cleared by hardware. If the Stream is used only once, this step might
     be bypassed. */
  while (DMA_GetCmdStatus(DMA_STREAM) != DISABLE)
  {
  }
  
  /* Configure DMA Stream */
  DMA_InitStructure.DMA_Channel = DMA_CHANNEL;  
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)aSRC_Const_Buffer;
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)aDST_Buffer;
  DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToMemory;
  DMA_InitStructure.DMA_BufferSize = (uint32_t)BUFFER_SIZE;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Enable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;         
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(DMA_STREAM, &DMA_InitStructure);
   
  /* Enable DMA Stream Transfer Complete interrupt */
  DMA_ITConfig(DMA_STREAM, DMA_IT_TC, ENABLE);


  /* DMA Stream enable */
  DMA_Cmd(DMA_STREAM, ENABLE);


  /* Check if the DMA Stream has been effectively enabled.
     The DMA Stream Enable bit is cleared immediately by hardware if there is an
     error in the configuration parameters and the transfer is no started (ie. when
     wrong FIFO threshold is configured ...) */
  Timeout = TIMEOUT_MAX;
  while ((DMA_GetCmdStatus(DMA_STREAM) != ENABLE) && (Timeout-- > 0))
  {
  }
   
  /* Check if a timeout condition occurred */
  if (Timeout == 0)
  {
    /* Manage the error: to simplify the code enter an infinite loop */
    while (1)
    {
    }
  }


  /* Enable the DMA Stream IRQ Channel */
  NVIC_InitStructure.NVIC_IRQChannel = DMA_STREAM_IRQ;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);     
}

eric2013

void I2SDMA_Start(void)
{         
    DMA_Cmd(DMA1_Stream4, ENABLE);
   
    /*
       检测DMA通道是否被正确的使能。
       如果DMA配置错误的话，使能位会被硬件清除，从而使得DMA无法启动。
       比如DMA的FIFO配置错误等等都会导致使能位被硬件清除。
    */
    while(DMA_GetCmdStatus(DMA1_Stream4) != ENABLE)
    {
    }
}
void I2SDMA_Stop(void)
{        
    DMA_Cmd(DMA1_Stream4, DISABLE);
    /*
      检查DMA是否被成功的禁止，只有成功禁止了，才能进行DMA的配置。
      Note：相同的DMA_Stream被多次配置的话，这一步就尤其重要了。在不过的禁止，使能，禁止，使能
      DMA通道的过程中，只有数据传输结束了，DMA禁止才有效。只有DMA被禁止的情况下，重新配置才有效。
      当然，如果只配置一次，这一步可以忽略。
    */
    while(DMA_GetCmdStatus(DMA1_Stream4) != DISABLE)
    {
    }
}

eric2013

贴代码好乱，还是发截图吧，截图方便不用整理：