Sample code/C/LCD

To test that the Linux framebuffer is set up correctly, and that the device permissions are correct, use the program below which opens the frame buffer and draws a gradient-filled red square. Original on http://doc.trolltech.com/4.2/qtopiacore-testingframebuffer.html

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 == -1) { perror("Error: cannot open framebuffer device"); exit(1); }    printf("The framebuffer device was opened successfully.\n"); // Get fixed screen information if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) { perror("Error reading fixed information"); exit(2); }    // Get variable screen information if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) { perror("Error reading variable information"); 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; // Map the device to memory fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0); if ((int)fbp == -1) { perror("Error: failed to map framebuffer device to memory"); 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++) { location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length; 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 } 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;             } }    munmap(fbp, screensize); close(fbfd); return 0; }
 * 1) include 
 * 2) include 
 * 3) include 
 * 4) include 
 * 5) include 
 * 6) include 
 * 7) include 