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Altera_Forum's avatar
Altera_Forum
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13 years ago

use descriptor chain in SGDMA

Hi all My current goal is to use SGDMA (ST-to-MM) to transfer video data to a memory. Later on, I'll replace the memory by PCIE IP. My problem is how to use descriptor chain in SGDMA. ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

The problem is solved. I add a delay after the SGDMA transfer and the descriptor chain works. I guess that a too frequent SGDMA transfer may cause this problem.

The modified code is as follows: 


while(1)
{
// clear buf
memset(buf, 0, sizeof(buf));
// write single descriptor
alt_avalon_sgdma_construct_stream_to_mem_desc(&sgdma_desc, &sgdma_desc, buf, 0, 0);
alt_avalon_sgdma_construct_stream_to_mem_desc(&sgdma_desc, &sgdma_desc, &buf, 0, 0);
// enable SGDMA
alt_avalon_sgdma_do_async_transfer(sgdma_dev, &sgdma_desc);
usleep(10000);	// must add this sleep
}