原创 Nios II DMA:多次发起

本程序首先输出目标地址空间的数据，然后连续发起两次DMA传输，最后再次输出DMA传输后目标地址空间的数据。<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

第二次发起可以在第一次DMA传输没有结束的情况下开始，不过要注意，两次的目标地址不能有重叠部分，否则发起会失败。

#include <stdio.h>

#include <stdlib.h>

#include "unistd.h"

#include "string.h"

#include "io.h"

#include "system.h"

#include "sys/alt_dma.h"

#include "sys/alt_cache.h"

#include "sys/alt_irq.h"

#include "alt_types.h"

#include "sys/alt_irq.h"

#include "altera_avalon_dma_regs.h"

#include "altera_avalon_uart_regs.h"

volatile char chr[20] = {1,2,3,4,6,5,7,8,9,10,

                        11,12,13,14,15,16,17,18,19,20} ;//数据源

volatile char chr2[20] = {1,2,3,4,6,5,7,8,9,10,

                        11,12,13,14,15,16,17,18,19,20} ;//数据源                       

static volatile int rx_done = 0;

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

{

rx_done++;

IOWR(LED_BASE,0, rx_done);//LED显示rx_done的变化

}

static void done2 (void* handle, void* data)

{

rx_done++;

IOWR(LED_BASE,0, rx_done);//LED显示rx_done的变化

}

int main (int argc, char* argv[], char* envp[])

{

alt_u8 i="0";

int rc;

alt_dma_txchan txchan;

alt_dma_rxchan rxchan;

void * tx_data = (void*) chr;

void * tx_data2 = (void*) chr2;

char *rx = (char *)ONCHIP_RAM_BASE;

char *rx2 = (char *)ONCHIP_RAM_BASE+20;

void* rx_buffer = (void*) ONCHIP_RAM_BASE;//0x00801000; /* pointer to rx buffer */

void* rx_buffer2 = (void*) ONCHIP_RAM_BASE+20;

IOWR(LED_BASE,0, 0);

for(i =0;i<20;i++)  //串口输出目标地址空间的数据

{

   printf ("%c",*(rx+i));

}

printf ("\n");

for(i =0;i<20;i++)  //串口输出目标地址空间的数据

{

   printf ("%c",*(rx2+i));

}

printf ("\n");

printf ("Let's begin!\n");

alt_dcache_flush_all();//清空数据缓存

if ((txchan = alt_dma_txchan_open("/dev/DMA0")) == NULL)

{

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

}

if ((rxchan = alt_dma_rxchan_open("/dev/DMA0")) == NULL)

{

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

}

rc = alt_dma_rxchan_depth(rxchan);//获取最大可接受请求数量

printf ("rxchan_depth = %d\n",rc);

rc = alt_dma_txchan_space(txchan);//获取最大发送请求数目

printf ("txchan_depth = %d\n",rc);

/******************第一次DMA请求******************/

if ((rc = alt_dma_txchan_send (txchan,

tx_data,

20,

NULL,

NULL)) < 0)

{

printf ("Failed to post transmit request1, reason = %i\n", rc);

}

if ((rc = alt_dma_rxchan_prepare (rxchan,

rx_buffer,

20,

done,

NULL)) < 0)

{

printf ("Failed to post read request1, reason = %i\n", rc);

}

/******************第二次DMA请求******************/

if ((rc = alt_dma_txchan_send (txchan,

tx_data2,

20,

NULL,

NULL)) < 0)

{

printf ("Failed to post transmit request2, reason = %i\n", rc);

}

if ((rc = alt_dma_rxchan_prepare (rxchan,

rx_buffer2,

20,

done2,

NULL)) < 0)

{

printf ("Failed to post read request2, reason = %i\n", rc);

}

while (rx_done<2);//等待两次发送完毕

printf ("Transfer successful!\n");

for(i =0;i<20;i++)

{

   printf ("%c",*(rx+i)); //再次输出dma传输后目标地址的数据

}

  printf ("\n");

for(i =0;i<20;i++)

{

   printf ("%c",*(rx2+i)); //再次输出dma传输后目标地址的数据

}

  printf ("\n"); 

  while(1);

return 0;

}