Strange error with NIOS2 DMA ..

hello to everyone i am trying to make my DMA read from a PIO and write in a SDRAM

This is my adapted code to do this

Code:

#include <stdio.h>

#include <stdlib.h>

#include <stddef.h>

#include <string.h>

#include <system.h>

#include <io.h>

#include <alt_types.h>

#include "sys/alt_dma.h"

#include "sys/alt_cache.h"

#include "sys/alt_alarm.h"

#include "alt_types.h"

int i;

static volatile int txrx_done = 0;

//callback function when DMA transfer done

static void txrxDone(void * handle, void * data)

{

txrx_done = 1;

}

void initMEM(int base_addr,int len)

{

for ( i=0;i<len;i++)

{

IOWR_8DIRECT(base_addr,i,i);

}

}

int main()

{

printf("testing onchip & sdram : dma operation\n");

alt_16 buffer[10];

//memset((void *)SSRAM_0_BASE,0x7a,0x10);//this write base on byte

// initMEM(ONCHIP_MEMORY2_1_BASE,0x10);

memset((void *)(SDRAM_0_BASE),0x33,0x10);

printf("content of onchip:before DMA operation\n");

for ( i=0;i<0x10;i++)

{

printf("%d: %x\n",i,IORD_8DIRECT(DMA_0_READ_MASTER_ENTRADA_FIFO_BASE,i));

}

printf("content of sdram_1:before DMA operation\n");

for ( i=0;i<0x10;i++)

{

printf("%d: %x\n",i,IORD_8DIRECT(SDRAM_0_BASE,i));

}

int rc; //request

alt_dma_txchan txchan;

alt_dma_rxchan rxchan;

void* tx_data = (void*)DMA_0_READ_MASTER_ENTRADA_FIFO_BASE; /* pointer to data to send */

void* rx_buffer = (void*)(SDRAM_0_BASE); /* pointer to rx buffer */

/* Create the transmit channel */

if ((txchan = alt_dma_txchan_open("/dev/dma_0")) == NULL)

{

printf ("Failed to open transmit channel\n");

exit (1);

}

/* Create the receive channel */

if ((rxchan = alt_dma_rxchan_open("/dev/dma_0")) == NULL)

{

printf ("Failed to open receive channel\n");

exit (1);

}

/* Post the transmit request */

if ((rc = alt_dma_txchan_send (txchan,

tx_data,

0x10,

NULL,

NULL)) < 0)

{

printf ("Failed to post transmit request, reason = %i\n", rc);

//exit (1);

}

/* Post the receive request */

if ((rc = alt_dma_rxchan_prepare (rxchan,

rx_buffer,

0x10,

txrxDone,

NULL)) < 0)

{

printf ("Failed to post read request, reason = %i\n", rc);

//exit (1);

}

/* wait for transfer to complete */

while (!txrx_done);

printf ("Transfer successful!\n");

printf("content of onchip:after DMA operation\n");

for ( i=0;i<0x10;i++)

{

printf("%d: %x\n",i,IORD_8DIRECT(DMA_0_READ_MASTER_ENTRADA_FIFO_BASE,i));

}

printf("content of sdram_1:after DMA operation\n");

for ( i=0;i<0x10;i++)

{

printf("%d: %x\n",i,IORD_8DIRECT(SDRAM_0_BASE,i));

}

return 0;

}

this is my output

[code]

it starts reading from my SDRAM (1: FF, 2:FF..)but when it reads the fitfh addres it starts to appear [][][][][][[][][][][][][][][[][][][][][][][][[][][] .. etc

really weird.. what could it be