2025-10-28

veosat
一生一芯
2025-10-28
42热度
0评论

键盘实现也很简单，代码如下

#define KEYDOWN_MASK 0x8000
void __am_input_keybrd(AM_INPUT_KEYBRD_T *kbd) {

  uint32_t KEY;
  KEY=inl(KBD_ADDR);

  kbd->keydown = 0;
  kbd->keycode = AM_KEY_NONE;

  if(KEY&KEYDOWN_MASK){
    kbd->keydown = 1;
    kbd->keycode = (int)(KEY&~KEYDOWN_MASK);
  }
  else {
    kbd->keydown = 0;
    kbd->keycode = (int)(KEY&~KEYDOWN_MASK);
  }

}

<span class="line"><span style="color: #af00db;">#define</span>
<span style="color: #0000ff;"> KEYDOWN_MASK </span>
<span style="color: #098658;">0x8000</span></span>
<span class="line"><span style="color: #0000ff;">void</span> <span style="color: #795e26;">__am_input_keybrd</span>
<span style="color: #000000;">(AM_INPUT_KEYBRD_T *</span>
<span style="color: #001080;">kbd</span>
<span style="color: #000000;">) {</span></span>

<span class="line">  <span style="color: #0000ff;">uint32_t</span>
<span style="color: #000000;"> KEY;</span></span>
<span class="line"><span style="color: #000000;">  KEY=</span>
<span style="color: #795e26;">inl</span>
<span style="color: #000000;">(KBD_ADDR);</span></span>

<span class="line">  <span style="color: #001080;">kbd</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">keydown</span>
<span style="color: #000000;"> = </span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;</span></span>
<span class="line">  <span style="color: #001080;">kbd</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">keycode</span>
<span style="color: #000000;"> = AM_KEY_NONE;</span></span>

<span class="line">  <span style="color: #af00db;">if</span>
<span style="color: #000000;">(KEY&KEYDOWN_MASK){</span></span>
<span class="line">    <span style="color: #001080;">kbd</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">keydown</span>
<span style="color: #000000;"> = </span>
<span style="color: #098658;">1</span>
<span style="color: #000000;">;</span></span>
<span class="line">    <span style="color: #001080;">kbd</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">keycode</span>
<span style="color: #000000;"> = (</span>
<span style="color: #0000ff;">int</span>
<span style="color: #000000;">)(KEY&~KEYDOWN_MASK);</span></span>
<span class="line"><span style="color: #000000;">  }</span></span>
<span class="line">  <span style="color: #af00db;">else</span>
<span style="color: #000000;"> {</span></span>
<span class="line">    <span style="color: #001080;">kbd</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">keydown</span>
<span style="color: #000000;"> = </span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;</span></span>
<span class="line">    <span style="color: #001080;">kbd</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">keycode</span>
<span style="color: #000000;"> = (</span>
<span style="color: #0000ff;">int</span>
<span style="color: #000000;">)(KEY&~KEYDOWN_MASK);</span></span>
<span class="line"><span style="color: #000000;">  }</span></span>

<span class="line"><span style="color: #000000;">}</span></span>

需要注意从寄存器获取的值最高位代表是按下还是松开，需要去掉最高位再返回给应用程序，否则会产生数组越界。

VGA这部分做起来意外的顺利。屏幕大小寄存器就是vgactl_port_base[0]寄存器，宽度在高16位，高度在低16位，那么自然同步寄存器就是vga_port_base[1]了，按照nemu中vga的注释，同步寄存器这样使用

void vga_update_screen(){
  if(vgactl_port_base[1]&0x1){
    update_screen();
    vgactl_port_base[1]=0;
  }
}

<span class="line"><span style="color: #0000ff;">void</span> <span style="color: #795e26;">vga_update_screen</span>
<span style="color: #000000;">(){</span></span>
<span class="line">  <span style="color: #af00db;">if</span>
<span style="color: #000000;">(</span>
<span style="color: #001080;">vgactl_port_base</span>
<span style="color: #000000;">[</span>
<span style="color: #098658;">1</span>
<span style="color: #000000;">]&</span>
<span style="color: #098658;">0x1</span>
<span style="color: #000000;">){</span></span>
<span class="line">    <span style="color: #795e26;">update_screen</span>
<span style="color: #000000;">();</span></span>
<span class="line">    <span style="color: #001080;">vgactl_port_base</span>
<span style="color: #000000;">[</span>
<span style="color: #098658;">1</span>
<span style="color: #000000;">]=</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;</span></span>
<span class="line"><span style="color: #000000;">  }</span></span>
<span class="line"><span style="color: #000000;">}</span></span>

一开始我以为这个也要做成回调函数，但是看函数的声明不是这样的，只需要这样写就能实现屏幕的更新。另外现在AM_GPU_FBDRAW的功能也不对，现在的代码只向nemu发出更新命令，没有把图像送到显存，添加如下代码

void __am_gpu_fbdraw(AM_GPU_FBDRAW_T *ctl) {
  uint32_t ctrl0;
  int w=0;
  ctrl0 = inl(VGACTL_ADDR);
  w = ctrl0>>16;
  uint32_t *fb=(uint32_t *)(uintptr_t)FB_ADDR;
  int32_t *pixel=(int32_t*)ctl->pixels;
  for(int i=0;ih;i++){
    for(int j=0;jw;j++){
      fb[ ctl->y*w+ctl->x + i*w+j]=*pixel;
      pixel++;
    }
  }
  if (ctl->sync) {
    outl(SYNC_ADDR, 1);
  }
}

<span class="line"><span style="color: #0000ff;">void</span> <span style="color: #795e26;">__am_gpu_fbdraw</span>
<span style="color: #000000;">(AM_GPU_FBDRAW_T *</span>
<span style="color: #001080;">ctl</span>
<span style="color: #000000;">) {</span></span>
<span class="line">  <span style="color: #0000ff;">uint32_t</span>
<span style="color: #000000;"> ctrl0;</span></span>
<span class="line">  <span style="color: #0000ff;">int</span>
<span style="color: #000000;"> w=</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;</span></span>
<span class="line"><span style="color: #000000;">  ctrl0 = </span>
<span style="color: #795e26;">inl</span>
<span style="color: #000000;">(VGACTL_ADDR);</span></span>
<span class="line"><span style="color: #000000;">  w = ctrl0>></span>
<span style="color: #098658;">16</span>
<span style="color: #000000;">;</span></span>
<span class="line">  <span style="color: #0000ff;">uint32_t</span>
<span style="color: #000000;"> *fb=(</span>
<span style="color: #0000ff;">uint32_t</span>
<span style="color: #000000;"> *)(</span>
<span style="color: #0000ff;">uintptr_t</span>
<span style="color: #000000;">)FB_ADDR;</span></span>
<span class="line">  <span style="color: #0000ff;">int32_t</span>
<span style="color: #000000;"> *pixel=(</span>
<span style="color: #0000ff;">int32_t</span>
<span style="color: #000000;">*)</span>
<span style="color: #001080;">ctl</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">pixels</span>
<span style="color: #000000;">;</span></span>
<span class="line">  <span style="color: #af00db;">for</span>
<span style="color: #000000;">(</span>
<span style="color: #0000ff;">int</span>
<span style="color: #000000;"> i=</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;i<</span>
<span style="color: #001080;">ctl</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">h</span>
<span style="color: #000000;">;i++){</span></span>
<span class="line">    <span style="color: #af00db;">for</span>
<span style="color: #000000;">(</span>
<span style="color: #0000ff;">int</span>
<span style="color: #000000;"> j=</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;j<</span>
<span style="color: #001080;">ctl</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">w</span>
<span style="color: #000000;">;j++){</span></span>
<span class="line">      <span style="color: #001080;">fb</span>
<span style="color: #000000;">[ </span>
<span style="color: #001080;">ctl</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">y</span>
<span style="color: #000000;">*w+</span>
<span style="color: #001080;">ctl</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">x</span>
<span style="color: #000000;"> + i*w+j]=*pixel;</span></span>
<span class="line"><span style="color: #000000;">      pixel++;</span></span>
<span class="line"><span style="color: #000000;">    }</span></span>
<span class="line"><span style="color: #000000;">  }</span></span>
<span class="line">  <span style="color: #af00db;">if</span>
<span style="color: #000000;"> (</span>
<span style="color: #001080;">ctl</span>
<span style="color: #000000;">-></span>
<span style="color: #001080;">sync</span>
<span style="color: #000000;">) {</span></span>
<span class="line">    <span style="color: #795e26;">outl</span>
<span style="color: #000000;">(SYNC_ADDR, </span>
<span style="color: #098658;">1</span>
<span style="color: #000000;">);</span></span>
<span class="line"><span style="color: #000000;">  }</span></span>
<span class="line"><span style="color: #000000;">}</span></span>

这里我默认屏幕左上角是坐标原点，x轴向右延申，y轴向下延申，这个影响不大，就算不正确应该也只是导致图像反转。完成后gpu就可以显示图像了，去掉__am_gpu_init()中的测试代码，运行display test的结果如下

色块会旋转，这里是静态图片展示。估计是因为性能孱弱的原因，FPS只有1

实现VGA之后，再运行demo里的程序，例如兰顿蚂蚁，结果如下。其他的不再演示。

激动人心的时刻到了：用NEMU运行NES模拟器！上来就出错了，提示NES文件打开权限错误，检查了一下模拟器的代码，发现是这里报错的

bool read = !strcmp(mode,"rb");
bool write = !strcmp(mode,"wb");
if((read&&write)||(!read&&!write)){
  FCEU_PrintError("invalid file open mode specified (only wb and rb are supported)");
  ..

<span class="line"><span style="color: #0000ff;">bool</span>
<span style="color: #000000;"> read = !</span>
<span style="color: #795e26;">strcmp</span>
<span style="color: #000000;">(mode,</span>
<span style="color: #a31515;">"rb"</span>
<span style="color: #000000;">);</span></span>
<span class="line"><span style="color: #0000ff;">bool</span>
<span style="color: #000000;"> write = !</span>
<span style="color: #795e26;">strcmp</span>
<span style="color: #000000;">(mode,</span>
<span style="color: #a31515;">"wb"</span>
<span style="color: #000000;">);</span></span>
<span class="line"><span style="color: #af00db;">if</span>
<span style="color: #000000;">((read&&write)||(!read&&!write)){</span></span>
<span class="line">  <span style="color: #795e26;">FCEU_PrintError</span>
<span style="color: #000000;">(</span>
<span style="color: #a31515;">"invalid file open mode specified (only wb and rb are supported)"</span>
<span style="color: #000000;">);</span></span>
<span class="line"><span style="color: #000000;">  ..</span></span>

printf大法试了下，发现read和write竟然都是1，那么肯定是klib的strcmp实现错了，检查代码果然如此

int strcmp(const char *s1, const char *s2) {
  int cmp=0;
  int8_t s1_s2=0;
  size_t cnt=0;
  while(*(s1+cnt)!='\0'&&*(s2+cnt)!='\0'){
    s1_s2=*(s1+cnt)-*(s2+cnt);
    cmp = (s1_s2>0) ? 1 : ( (s1_s2<0) ? -1 : 0 );
    cnt++;
  }
  return cmp;
  //panic("Not implemented");
}

<span class="line"><span style="color: #0000ff;">int</span> <span style="color: #795e26;">strcmp</span>
<span style="color: #000000;">(</span>
<span style="color: #0000ff;">const</span> <span style="color: #0000ff;">char</span>
<span style="color: #000000;"> *</span>
<span style="color: #001080;">s1</span>
<span style="color: #000000;">, </span>
<span style="color: #0000ff;">const</span> <span style="color: #0000ff;">char</span>
<span style="color: #000000;"> *</span>
<span style="color: #001080;">s2</span>
<span style="color: #000000;">) {</span></span>
<span class="line">  <span style="color: #0000ff;">int</span>
<span style="color: #000000;"> cmp=</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;</span></span>
<span class="line">  <span style="color: #0000ff;">int8_t</span>
<span style="color: #000000;"> s1_s2=</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;</span></span>
<span class="line">  <span style="color: #0000ff;">size_t</span>
<span style="color: #000000;"> cnt=</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">;</span></span>
<span class="line">  <span style="color: #af00db;">while</span>
<span style="color: #000000;">(*(s1+cnt)!=</span>
<span style="color: #a31515;">'</span>
<span style="color: #ee0000;">\0</span>
<span style="color: #a31515;">'</span>
<span style="color: #000000;">&&*(s2+cnt)!=</span>
<span style="color: #a31515;">'</span>
<span style="color: #ee0000;">\0</span>
<span style="color: #a31515;">'</span>
<span style="color: #000000;">){</span></span>
<span class="line"><span style="color: #000000;">    s1_s2=*(s1+cnt)-*(s2+cnt);</span></span>
<span class="line"><span style="color: #000000;">    cmp = (s1_s2></span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">) ? </span>
<span style="color: #098658;">1</span>
<span style="color: #000000;"> : ( (s1_s2<</span>
<span style="color: #098658;">0</span>
<span style="color: #000000;">) ? -</span>
<span style="color: #098658;">1</span>
<span style="color: #000000;"> : </span>
<span style="color: #098658;">0</span>
<span style="color: #000000;"> );</span></span>
<span class="line"><span style="color: #000000;">    cnt++;</span></span>
<span class="line"><span style="color: #000000;">  }</span></span>
<span class="line">  <span style="color: #af00db;">return</span>
<span style="color: #000000;"> cmp;</span></span>
<span class="line">  <span style="color: #008000;">//panic("Not implemented");</span></span>
<span class="line"><span style="color: #000000;">}</span></span>

其实是对strcmp的行为理解有误，在对比到第一个不相等的字符的时候比较就结束了才对，而不是一直比较到字符串结束，修改一下，模拟器启动！

加载ROM就用了十几秒，帧率有0帧或者1帧，一开始我以为自己实现错了，屏幕一直没动，过了一分钟终于出现了熟悉的界面：看来设备这块应该是通了