dma范例.txt

NiosII初学者范例,里面包含字符模式设备驱动DMA传输等范例

/*
 * 声明：本范例源于书籍‘NiosII软件架构解析’
 * 作者：蔡伟纲
 * 博客地址： http://NiosII.cublog.cn 
 *
 * 一、功能: DMA(Memory to Memory)驱动演示代码.
 * 二、运行前提: 本范例需要硬件开发板的支持,
 *     要求NiosII系统包含名为”dma”的DMA模块,
 *     且DMA的长度寄存器应当大于10位,支持字传输;
*/
#include <stdio.h>
#include <stdlib.h>
#include "sys/alt_dma.h"
#include "altera_avalon_dma_regs.h"
#include "system.h"
#include <sys/alt_cache.h>

//定义DMA传输长度
#define TRANSFER_LENGTH 1024

static volatile int rx_done = 0;

//定义DMA传输结束后的回调函数,它将在DMA传输结束后被系统自动调用;
//通过简单的rx_done++,可告知主程序DMA已经完成传输任务;
static void done(void* handle, void* data)
{
  rx_done++;
}


int main(int argc, char* argv[], char* envp[])
{
  printf ("DMA Demo(Memory to Memory)!\n");

  int return_code;
  alt_dma_txchan txchan;
  alt_dma_rxchan rxchan;
      
  //开辟源缓冲区,本范例将把源缓冲区的数据传输到目的缓冲区;
  //TRANSFER_LENGTH不可过大,否则可能导致堆栈溢出; 
  char source[TRANSFER_LENGTH]; 
  //开辟目的缓冲区,该缓冲区将接收来自DMA接收通道的数据;
  //并通过与源缓冲区数据的对比来确定DMA传输是否正确;
  //TRANSFER_LENGTH不可过大,否则可能导致堆栈溢出; 
  char dest[TRANSFER_LENGTH];
  
  //将源缓冲区的数据全部初始化为0x55;
  memset(source, 0x55, TRANSFER_LENGTH);
  //清空数据缓存,确保源缓冲区的数据正确初始化;
  alt_dcache_flush_all();
       
  //创建DMA发送通道;
  if((txchan = alt_dma_txchan_open("/dev/dma")) == NULL)
  {
    printf ("Failed to open transmit channel\n");
    exit(1);
  }
  else
  {
    printf ("Create the transmit channel successfully!\n");  
  }

  //创建DMA接收通道;
  if((rxchan = alt_dma_rxchan_open("/dev/dma")) == NULL)
  {
    printf ("Failed to open receive channel\n");
    exit(1);
  }
  else
  {
    printf ("Create the receive channel successfully!\n");  
  }

  //提交DMA发送请求;
  if((return_code = alt_dma_txchan_send(txchan,
                                        source,
                                        TRANSFER_LENGTH,
                                        NULL,
                                        NULL)) < 0)
  {
    printf ("Failed to post transmit request, reason = %i\n", return_code);
    exit (1);
  }
  else
  {
    printf ("Post the transmit request successfully!\n");  
  }
  
  //提交DMA接收请求;
  if ((return_code = alt_dma_rxchan_prepare(rxchan,
                                            dest,
                                            TRANSFER_LENGTH,
                                            done,
                                            NULL)) < 0)
  {
    printf ("Failed to post read request, reason = %i\n", return_code);
    exit (1);
  }
  else
  {
    printf ("Post the receive request successfully!\n");  
  }
    
  //等待DMA传输结束;
  while(rx_done == 0);
  
  int Loop, ErrorCount = 0;
  for(Loop = 0; Loop < TRANSFER_LENGTH; Loop++)
  {
    //对比源缓冲区和目的缓冲区的数据;
    if(source[Loop] != dest[Loop])
    {
      printf("Verify failed at location: 0x%X\n",Loop);
      ErrorCount++;
    }  
  } 
  
  if(ErrorCount == 0)
  {
    printf ("Transfer successfully!\n");
  }  
  else
  {  
    printf("Transfer failed!\n");
  }
  
  while(1);
}