Can't Read Data from Custom componet (Avalon mm)

alt_dma_txchan_ioctl is a higher level HAL function ;).

With that code you will configure it to perform word transfers. And you will be constantly writing to the same address (tx_data_to) and the reading address increments by 0x04 after each read.

You can use the code on page 29 of the document Daixiwen linked.

Just add the configuration like this:

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

{

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

exit (1);

}

else

{

alt_dma_txchan_ioctl(txchan, ALT_DMA_SET_MODE_32, NULL);

alt_dma_txchan_ioctl(txchan, ALT_DMA_TX_ONLY_ON, tx_data_to);

alt_dma_txchan_ioctl(txchan, ALT_DMA_RX_ONLY_OFF, NULL);

}