questions about DMA transmition

[Altera_Forum]

hi: 

I want to transmit data from FIFO to sdram by DMA in SOPC builder.  in NIOSII eclipse,    if((tx=alt_avalon_dma_send(txchan,(void*)tx_data,0x1000,NULL,NULL))<0)  {  printf("failed to send data from fifo \n"); )  always printf: failed to send data from fifo  I add "while(1)" to contain this code:  while(1)  { //the number of translated data at one time  for(j=0;j<=100;j++)  {  if((tx=alt_avalon_dma_send(txchan,(void*)tx_data,0x1000,NULL,NULL))<0)  {  printf("failed to send data from fifo \n"); //  }  if( j==90)  exit(1);  }    but it always failed ...    is there somebody can give me any hints? thanks~

[Altera_Forum]

hi,gurus  

I have try lots of times ,but always failed,so I hope someone can give me help~  the self-made SOPC component is connected to read master port of DMA, SDRAM is connected to write master port of DMA.  the setl-made component is connected to avalon bus as a slave interface.when I use "IORD"to read the component,it is right,but when I connect is to DMA,DMA transmits failed~    if((rx= alt_avalon_dma_prepare(rxchan,rx_buffer,1024,done_t,NULL))<0)  {  printf("rxchan receive failed.reason: %d",rx);  exit(1);  }  dma_prepare always failed, if the self-made component has some problems (the component consist of a FIFO which connected to avalon through slave port )??       The NiosII software code is attached the pogrammme is very urge,and there is nobody around me can give me advise,so I hope you gurus can give me some hints~ thanks very much~~

[Altera_Forum]

/* begin receive data*/ 

if((rx= alt_avalon_dma_prepare(rxchan,rx_buffer,1024,done_t,NULL))<0)  {  printf("rxchan receive failed.reason: %d",rx);  exit(1);  } after running,niosII console:  rx=-28;  I check the meaning of "28" in altera_avalon_dma.h:  start = priv->tx_start;  end = priv->tx_end;  slot = &priv->tx_buf[end];  next = (end + 1) & ALT_AVALON_DMA_NSLOTS_MSK;  if (next == start)  {  return -ENOSPC;  } so I guess that there is no room in memory,but I am not sure which memory has no room and why it has no room,so I delete my signaltapII file so as to let more room off,but the error is still there.    I will keep trying~

[Altera_Forum]

hi, 

I have solved the above problem,that is ,the data writen into the FIFO can be transfered to the SDRAM by the DMA .  here I have some feelings which be shared with yours.  1: DMA transmition ,FIFO (slave port attached into Avalon bus) to SDRAM,because of reading the same address(FIFO base address),so you only need to open received channel(rxchan),and set iocl(mode,RX_only),then ,prepare .   2:there seems the SOPC can do lots for you,so you need not care about the details too much:)     best regards