Hi juancarlostiquerangel
I'm not knowledgeable enough in this area to give you advice, but:
Writing to /dev/fb0 should access the hdmi interface when the device scans for output data.
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <unistd.h>
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) {
// Handle errors
}
// Get fixed screen information
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {
// Handle errors
}
// Get variable screen information
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
// Handle errors
}
// Figure out the size of the screen in bytes
screensize = vinfo.yres_virtual * finfo.line_length;
// Map the device to memory
fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
if ((intptr_t)fbp == -1) {
// Handle errors
}
// Draw a pixel on the screen at (x, y)
x = 100; y = 100; // Where we are going to put the pixel
// Calculate the pixel's location
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
}
// We'll unmap our memory and close the file
munmap(fbp, screensize);
close(fbfd);
return 0;
}
Alternatively you can use a graphical environment and just set the window to fullscreen 😉
Hope this helps.
Jaka
