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 :
1 /*
2 This file present all abstraction needed to port LiteNES.
3 (The current working implementation uses allegro library.)
4
5 To port this project, replace the following functions by your own:
6 1) nes_hal_init()
7 Do essential initialization work, including starting a FPS HZ timer.
8
9 2) nes_set_bg_color(c)
10 Set the back ground color to be the NES internal color code c.
11
12 3) nes_flush_buf(*buf)
13 Flush the entire pixel buf‘s data to frame buffer.
14
15 4) nes_flip_display()
16 Fill the screen with previously set background color, and
17 display all contents in the frame buffer.
18
19 5) wait_for_frame()
20 Implement it to make the following code is executed FPS times a second:
21 while (1) {
22 wait_for_frame();
23 do_something();
24 }
25
26 6) int nes_key_state(int b)
27 Query button b‘s state (1 to be pressed, otherwise 0).
28 The correspondence of b and the buttons:
29 0 - Power
30 1 - A
31 2 - B
32 3 - SELECT
33 4 - START
34 5 - UP
35 6 - DOWN
36 7 - LEFT
37 8 - RIGHT
38 */
39 #include "hal.h"
40 #include "fce.h"
41 #include "common.h"
42
43 /**
44 * allegro API 不明白的看文档
45 * https://www.allegro.cc/manual/5/index.html
46 */
47 /* lcd 操作相关 头文件 */
48 #include <sys/types.h>
49 #include <sys/stat.h>
50 #include <fcntl.h>
51 #include <linux/fb.h>
52 #include <sys/ioctl.h>
53 #include <unistd.h>
54 #include <string.h>
55 #include <sys/mman.h>
56
57 static int fb_fd;
58 static unsigned char *fb_mem;
59 static int px_width;
60 static int line_width;
61 static int screen_width;
62 static struct fb_var_screeninfo var;
63
64 static int lcd_fb_display_px(int color, int x, int y)
65 {
66 unsigned char *pen8;
67 unsigned short *pen16;
68
69 unsigned char r,g,b;
70
71 pen8 = (unsigned char *)(fb_mem + y*line_width + x*px_width);
72 pen16 = (unsigned short *)pen8;
73
74 //合并为 565 格式 16bbp
75 r = (color>>16) & 0xff;
76 g = (color>>8) & 0xff;
77 b = (color>>0) & 0xff;
78 *pen16 = (r>>3)<<11 | (g>>2)<<5 | (b>>3);
79
80 return 0;
81 }
82
83 //调色板转16进行32位颜色
84 static int pal2color(pal pal)
85 {
86 int color = 0;
87 color = pal.r << 16 | pal.g <<8 | pal.b;
88 return color;
89 }
90
91 static int lcd_fb_init()
92 {
93 //如果使用 mmap 打开方式 必须是 读定方式
94 fb_fd = open("/dev/fb0", O_RDWR);
95 if(-1 == fb_fd)
96 {
97 printf("cat‘t open /dev/fb0 \n");
98 return -1;
99 }
100 //获取屏幕参数
101 if(-1 == ioctl(fb_fd, FBIOGET_VSCREENINFO, &var))
102 {
103 close(fb_fd);
104 printf("cat‘t ioctl /dev/fb0 \n");
105 return -1;
106 }
107 //计算参数
108 px_width = var.bits_per_pixel / 8;
109 line_width = var.xres * px_width;
110 screen_width = var.yres * line_width;
111
112 fb_mem = (unsigned char *)mmap(NULL, screen_width, PROT_READ | PROT_WRITE, MAP_SHARED, fb_fd, 0);
113 if(fb_mem == (void *)-1)
114 {
115 close(fb_fd);
116 printf("cat‘t mmap /dev/fb0 \n");
117 return -1;
118 }
119 //清屏
120 memset(fb_mem, 0 , screen_width);
121 return 0;
122 }
123
124 /* Wait until next allegro timer event is fired. */
125 void wait_for_frame()
126 {
127 //休眠 FPS = 60 * 1000 毫秒
128 usleep(1/FPS*1000);
129 }
130
131 /* Set background color. RGB value of c is defined in fce.h */
132 void nes_set_bg_color(int c)
133 {
134 //画背景颜色
135 int i,j;
136 for(i=0; i<SCREEN_WIDTH; i++)
137 {
138 for(j=0; j<SCREEN_HEIGHT; j++)
139 {
140 lcd_fb_display_px(pal2color(palette[c]), i, j);
141 }
142 }
143 }
144
145 /* Flush the pixel buffer */
146 void nes_flush_buf(PixelBuf *buf)
147 {
148 Pixel *p;
149 int i,x,y,color;
150 for (i = 0; i < buf->size; i++)
151 {
152 p = &buf->buf[i];
153 x = p->x;
154 y = p->y;
155
156 color = pal2color(palette[p->c]);
157 lcd_fb_display_px(color, x, y);
158 lcd_fb_display_px(color, x+1, y);
159 lcd_fb_display_px(color, x, y+1);
160 lcd_fb_display_px(color, x+1, y+1);
161 }
162 }
163
164 /* Initialization:
165 (1) start a 1/FPS Hz timer.
166 (2) register fce_timer handle on each timer event */
167 void nes_hal_init()
168 {
169 /**
170 * 需要完成的事情
171 * 1,初始化 lcd
172 * 2,初始化 定时器 先做简单的直接用系统延时
173 */
174 if(-1 == lcd_fb_init())
175 {
176 printf("lcd fb init error \n");
177 return ;
178 }
179 }
180
181 /* Update screen at FPS rate by allegro‘s drawing function.
182 Timer ensures this function is called FPS times a second. */
183 void nes_flip_display()
184 {
185 //设置64种颜色值 不必设置
186 }
187
188 /* Query a button‘s state.
189 Returns 1 if button #b is pressed. */
190 int nes_key_state(int b)
191 {
192 switch (b)
193 {
194 case 0: // On / Off
195 return 1;
196 case 1: // A
197 return 1;
198 case 2: // B
199 return 1;
200 case 3: // SELECT
201 return 1;
202 case 4: // START
203 return 1;
204 case 5: // UP
205 return 1;
206 case 6: // DOWN
207 return 1;
208 case 7: // LEFT
209 return 1;
210 case 8: // RIGHT
211 return 1;
212 default:
213 return 1;
214 }
215 }
时间： 2025-01-06 22:34:02