DMA to UART

[Altera_Forum]

I have downside program in order to realize transfer block data from onchip_memory to UART by DMA, however it doesn't work. The message shows the transter has completed, but there is no data transfered to UART. 

I don't know is there some problem with my program or system set?   --- Quote Start ---  #include <stdio.h># include <stddef.h># include <stdlib.h># include "sys/alt_dma.h"# include "alt_types.h"# include <system.h> /* flag used to indicate the transaction is complete */ volatile int dma_complete = 0; /* function that is called when the transaction completes */ void dma_done (void* handle) { dma_complete = 1; } int main (void) { char buffer[32]="welcome to my nios2 world"; alt_dma_txchan tx; /* Obtain a handle for the device */ if ((tx = alt_dma_txchan_open ("/dev/dma")) == NULL) { printf ("Error: failed to open device\n"); exit (1); } else { /* Post the receive request */ alt_dma_txchan_ioctl(tx,ALT_DMA_TX_ONLY_ON,UART_BASE); if (alt_dma_txchan_send (tx, buffer, 32, dma_done, NULL) < 0) { printf ("Error: failed to post receive request\n"); exit (1); } /* Wait for the transaction to complete */ while (!dma_complete); printf ("Transaction complete\n"); alt_dma_txchan_close (tx); } return 0; }   --- Quote End ---       --- Quote Start ---  nios2-terminal: connected to hardware target using UART on /dev/com1 at 115200 b aud nios2-terminal: (Use the IDE stop button or Ctrl-C to terminate) rrnnaattoo ooppeeee  --- Quote End ---