Cannot get BDMA (DMA channel) to work, but DMA works (DMA stream)

[Tuoman]

Hello, trying to get DMA transfer to work.

This does work fine:

 //INIT DMA
 
static void MX_DMA_Init(void)
{
 
  /* DMA controller clock enable */
  __HAL_RCC_DMA1_CLK_ENABLE();
 
  /* Configure DMA request hdma_memtomem_dma1_stream1 on DMA1_Stream1 */
  hdma_memtomem_dma1_stream1.Instance = DMA1_Stream1;
  hdma_memtomem_dma1_stream1.Init.Request = DMA_REQUEST_MEM2MEM;
  hdma_memtomem_dma1_stream1.Init.Direction = DMA_MEMORY_TO_MEMORY;
  hdma_memtomem_dma1_stream1.Init.PeriphInc = DMA_PINC_ENABLE;
  hdma_memtomem_dma1_stream1.Init.MemInc = DMA_MINC_ENABLE;
  hdma_memtomem_dma1_stream1.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
  hdma_memtomem_dma1_stream1.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
  hdma_memtomem_dma1_stream1.Init.Mode = DMA_NORMAL;
  hdma_memtomem_dma1_stream1.Init.Priority = DMA_PRIORITY_LOW;
  hdma_memtomem_dma1_stream1.Init.FIFOMode = DMA_FIFOMODE_ENABLE;
  hdma_memtomem_dma1_stream1.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;
  hdma_memtomem_dma1_stream1.Init.MemBurst = DMA_MBURST_SINGLE;
  hdma_memtomem_dma1_stream1.Init.PeriphBurst = DMA_PBURST_SINGLE;
  if (HAL_DMA_Init(&hdma_memtomem_dma1_stream1) != HAL_OK)
  {
    Error_Handler( );
  }
 
}
 
 //START DMA
if(HAL_DMA_Start(&hdma_memtomem_dma1_stream1, (uint32_t)tx_buffer, (uint32_t)d3buffer, RX_LENGTH) != HAL_OK)
	  {
	  Error_Handler();
	  }

Yet, this does not work:

//INIT DMA
  /* DMA controller clock enable */
  __HAL_RCC_BDMA_CLK_ENABLE();
 
  /* Configure DMA request hdma_memtomem_bdma1_channel3 on BDMA1_Channel3 */
  hdma_memtomem_bdma1_channel3.Instance = BDMA1_Channel3;
  hdma_memtomem_bdma1_channel3.Init.Direction = DMA_MEMORY_TO_MEMORY;
  hdma_memtomem_bdma1_channel3.Init.PeriphInc = DMA_PINC_ENABLE;
  hdma_memtomem_bdma1_channel3.Init.MemInc = DMA_MINC_ENABLE;
  hdma_memtomem_bdma1_channel3.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
  hdma_memtomem_bdma1_channel3.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
  hdma_memtomem_bdma1_channel3.Init.Mode = DMA_NORMAL;
  hdma_memtomem_bdma1_channel3.Init.Priority = DMA_PRIORITY_LOW;
  if (HAL_DMA_Init(&hdma_memtomem_bdma1_channel3) != HAL_OK)
  {
    Error_Handler( );
  }
 
//START DMA
if(HAL_DMA_Start(&hdma_memtomem_bdma1_channel3, (uint32_t)tx_buffer, (uint32_t)d3buffer, RX_LENGTH) != HAL_OK)
{
Error_Handler();
}

What might be the reason for this? What is the fundamental difference between these DMA units (stream vs channel)?

I'm using STM32H7B3 microcontroller. d3buffer is allocated as follows:

uint32_t __attribute__((section (".RAM_D3"))) d3buffer[16]  =
                                      {0};
 
Linker:
 
MEMORY:
...
  RAM_D3 (xrw)    : ORIGIN = 0x38000000,   LENGTH = 128K
...
 
 
  .RAM_D3 : {
  . = ALIGN(4);
  _sRAM_D3 = .;        /* create a global symbol at DTCMData start */
    . = ALIGN(4);
   _eRAM_D3 = .;        /* create a global symbol at DTCMData end */
   } >RAM_D3

[TDK · Accepted solution]

BDMA1 doesn't have access to SRAM3.

There is some useful information in the reference manual about these peripherals.

A BDMA "channel" is functionally equivalent to a DMA "stream". The latter uses the DMAMUX to map a stream to different request generators. In familites without a DMAMUX, a DMA stream needed to be mapped by selecting one of 8 or so channels.

[Tuoman]

Thank you! So I need to use the DMAMUX(manually) when using BDMA? I will try that. But if they are equivalent, I might as well stick with the DMA steam which works fine.