LCD测试程序

#include
#include
#include
#include
#include

    int main()
    {
        int fbfd = 0;
        struct fb_var_screeninfo vinfo;
        struct fb_fix_screeninfo finfo;
        long int screensize = 0;
        char *fbp = 0;
        int x = 0, y = 0;
        long int location = 0;

        // Open the file for reading and writing
        fbfd = open("/dev/fb0", O_RDWR);
        if (!fbfd) {
            printf("Error: cannot open framebuffer device.\n");
            exit(1);
        }
        printf("The framebuffer device was opened successfully.\n");

        // Get fixed screen information
        if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
            printf("Error reading fixed information.\n");
            exit(2);
        }

        // Get variable screen information
        if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
            printf("Error reading variable information.\n");
            exit(3);
        }

        printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);

        // Figure out the size of the screen in bytes
        screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
        //bits_per_pixel 为位数，一个字节为8位，bits_per_pixel/8 为一个像素占用的字节数

        // Map the device to memory
        fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
                           fbfd, 0);
        if ((int)fbp == -1) {
            printf("Error: failed to map framebuffer device to memory.\n");
            exit(4);
        }
        printf("The framebuffer device was mapped to memory successfully.\n");

        x = 100; y = 100;       // Where we are going to put the pixel

        // Figure out where in memory to put the pixel
        for (y = 100; y < 300; y++)
            for (x = 100; x < 300; x++) {
                                // 计算出显示坐标在分配内存区域的位置
                location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
                           (y+vinfo.yoffset) * finfo.line_length;
          // line_length= xres*bits_per_pixel/8
                if (vinfo.bits_per_pixel == 32) {
                    *(fbp + location) = 100;        // Some blue
                    *(fbp + location + 1) = 15+(x-100)/2;     // A little green
                    *(fbp + location + 2) = 200-(y-100)/5;    // A lot of red
                    *(fbp + location + 3) = 0;      // No transparency

                 // 24色需要4个字节填充，第四个字节填空
                } else  { //assume 16bpp
                    int b = 10;
                    int g = (x-100)/6;     // A little green
                    int r = 31-(y-100)/16;    // A lot of red
                    unsigned short int t = r<<11 | g << 5 | b;
                    *((unsigned short int*)(fbp + location)) = t; //强制转换为16位

               // 16 色需要2个字节填充，看是565 还是5551 格式
                }

            }
        munmap(fbp, screensize);
        close(fbfd);
        return 0;
    }
=============================================================

下面为我自己的320×240的显示屏的测试程序

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#include
#include
#include
#include

#include

// RGB: 565   // 16位
int main(void)
{
 int fd=0;
 struct fb_var_screeninfo usrinfo;                   // 用户参数设置
 struct fb_fix_screeninfo devinfo;                 // 屏幕物理参数设置
 unsigned long screensize=0;
 short * fdp;
 int x=0;int y=0;
 int i=0;
 
 unsigned long location=0;
 
 fd=open("/dev/fb0",O_RDWR);
 if (fd<0)
  {
  printf("open error\n");
  return -1;
  }
 
 if(ioctl(fd,FBIOGET_FSCREENINFO,&devinfo))
  {printf("error reading fix \n");
   return -1;}
 if(ioctl(fd,FBIOGET_VSCREENINFO,&usrinfo))
  {printf("error reading fix \n");
   return -1;}
 
 screensize=usrinfo.xres * usrinfo.yres* usrinfo.bits_per_pixel/8 ;   
 printf("screensize=%d",screensize);
 fdp=(short *)mmap(0,screensize,PROT_READ|PROT_WRITE, MAP_SHARED,fd,0);
 if ((int)fdp==-1)
  {printf("error reading fix \n");return -1;}
  
 //因为为16位色，所以占用两个字节，那么 line_length= xres*2=640;我的屏为320×240，

  // 所以占用了两行， 那么page Y 最大值就不能为240，应该是120，否则会出现超出SIZE错误
 for (y=0;y<120;y++)    
  for (x=0;x<640;x++)
   {
    location=x*usrinfo.bits_per_pixel/8+y*devinfo.line_length;
    int r=10,g=330,b=10; //(5,6,5)
    *(fdp+location)=(short)((r<<11)|(g<<5)|b);
    
    
    
    }
 munmap(fdp,screensize);
 close(fd);
 return 0;
}