nes 红白机模拟器 第1篇

对比了很多种，开源的 NES 模拟器 VirtuaNES , nestopia , FakeNES , FCEUX , InfoNES , LiteNES

最后决定使用 LiteNES 进行移值，它是由 mynes 移值而来。LiteNES 对 mynes 代码进行整理兼容了 C99 标准，编译时无警告。

https://github.com/NJUOS/LiteNES

https://github.com/yaglo/mynes

LiteNES , mynes  基于 Allegro ，Allegro 是一种提供底层画图，输入，定时器等支持的库。

LiteNES 全部抽象提取代码到 一个 hal.c 文件里面，修改移值十分方便。下面是修改后的样子，替换这个文件。

在修改下 Makefile 中的 gcc 改为 arm-linux-gcc 编译 即可在板子上出现 Game 画面了（经过测试，发现支持的游戏不多，有的载加不出来）

NES 移值第1篇，仅能出现画面。以后会更新添加声音，多线程，输入等。现在只为能显示出画面。

hal.c :

 /*
 This file present all abstraction needed to port LiteNES.
   (The current working implementation uses allegro library.)

 To port this project, replace the following functions by your own:
 1) nes_hal_init()
     Do essential initialization work, including starting a FPS HZ timer.

 2) nes_set_bg_color(c)
     Set the back ground color to be the NES internal color code c.

 3) nes_flush_buf(*buf)
     Flush the entire pixel buf's data to frame buffer.

 4) nes_flip_display()
     Fill the screen with previously set background color, and
     display all contents in the frame buffer.

 5) wait_for_frame()
     Implement it to make the following code is executed FPS times a second:
         while (1) {
             wait_for_frame();
             do_something();
         }

 6) int nes_key_state(int b)
     Query button b's state (1 to be pressed, otherwise 0).
     The correspondence of b and the buttons:
       0 - Power
       1 - A
       2 - B
       3 - SELECT
       4 - START
       5 - UP
       6 - DOWN
       7 - LEFT
       8 - RIGHT
 */
 #include "hal.h"
 #include "fce.h"
 #include "common.h"

 /**
  * allegro API 不明白的看文档
  * https://www.allegro.cc/manual/5/index.html
  */
 /* lcd 操作相关 头文件 */
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <linux/fb.h>
 #include <sys/ioctl.h>
 #include <unistd.h>
 #include <string.h>
 #include <sys/mman.h>

 static int fb_fd;
 static unsigned char *fb_mem;
 static int px_width;
 static int line_width;
 static int screen_width;
 static struct fb_var_screeninfo var;

 static int lcd_fb_display_px(int color, int x, int y)
 {
     unsigned char  *pen8;
     unsigned short *pen16;

     unsigned char r,g,b;

     pen8 = (unsigned char *)(fb_mem + y*line_width + x*px_width);
     pen16 = (unsigned short *)pen8;

     //合并为 565 格式 16bbp
     r = (color>>) & 0xff;
     g = (color>>) & 0xff;
     b = (color>>) & 0xff;
     *pen16 = (r>>)<< | (g>>)<< | (b>>);

     return ;
 }

 //调色板转16进行32位颜色
 static int pal2color(pal pal)
 {
     int color = ;
     color = pal.r <<  | pal.g << | pal.b;
     return color;
 }

 static int lcd_fb_init()
 {
     //如果使用 mmap 打开方式 必须是 读写方式
     fb_fd = open("/dev/fb0", O_RDWR);
     if(- == fb_fd)
     {
         printf("cat't open /dev/fb0 \n");
         return -;
     }
     //获取屏幕参数
     if(- == ioctl(fb_fd, FBIOGET_VSCREENINFO, &var))
     {
         close(fb_fd);
         printf("cat't ioctl /dev/fb0 \n");
         return -;
     }
     //计算参数
     px_width = var.bits_per_pixel / ;
     line_width = var.xres * px_width;
     screen_width = var.yres * line_width;

     fb_mem = (unsigned char *)mmap(NULL, screen_width, PROT_READ | PROT_WRITE, MAP_SHARED, fb_fd, );
     if(fb_mem == (void *)-)
     {
         close(fb_fd);
         printf("cat't mmap /dev/fb0 \n");
         return -;
     }
     //清屏
     memset(fb_mem,  , screen_width);
     return ;
 }

 /* Wait until next allegro timer event is fired. */
 void wait_for_frame()
 {
     //休眠 FPS = 60 * 1000 毫秒
     usleep(/FPS*);
 }

 /* Set background color. RGB value of c is defined in fce.h */
 void nes_set_bg_color(int c)
 {
     //画背景颜色
     int i,j;
     for(i=; i<SCREEN_WIDTH; i++)
     {
         for(j=; j<SCREEN_HEIGHT; j++)
         {
             lcd_fb_display_px(pal2color(palette[c]), i, j);
         }
     }
 }

 /* Flush the pixel buffer */
 void nes_flush_buf(PixelBuf *buf)
 {
     Pixel *p;
     int i,x,y,color;
     for (i = ; i < buf->size; i++)
     {
            p = &buf->buf[i];
            x = p->x;
         y = p->y;

         color = pal2color(palette[p->c]);
         lcd_fb_display_px(color, x, y);
         lcd_fb_display_px(color, x+, y);
         lcd_fb_display_px(color, x, y+);
         lcd_fb_display_px(color, x+, y+);
         }
 }

 /* Initialization:
    (1) start a 1/FPS Hz timer.
    (2) register fce_timer handle on each timer event */
 void nes_hal_init()
 {
     /**
      * 需要完成的事情
      * 1,初始化 lcd
      * 2,初始化 定时器 先做简单的直接用系统延时
      */
     if(- == lcd_fb_init())
     {
         printf("lcd fb init error \n");
         return ;
     }
 }

 /* Update screen at FPS rate by allegro's drawing function.
    Timer ensures this function is called FPS times a second. */
 void nes_flip_display()
 {
     //设置64种颜色值 不必设置
 }

 /* Query a button's state.
    Returns 1 if button #b is pressed. */
 int nes_key_state(int b)
 {
     switch (b)
     {
         case : // On / Off
             return ;
         case : // A
             return ;
         case : // B
             return ;
         case : // SELECT
             return ;
         case : // START
             return ;
         case : // UP
             return ;
         case : // DOWN
             return ;
         case : // LEFT
             return ;
         case : // RIGHT
             return ;
         default:
             return ;
     }
 }