tutorial framebuffer screen setup

1. connect vocore: connect vocore to your computer USB port, and use kermit connect to VoCore2 microUSB USB2TTL.
2. setup framebuffer: we need to insmod the screen driver, once insert into it, we will have a new device at /dev/fb0, then we can use the screen as common framebuffer screen.
3. connect to screen: connect the screen to VoCore's USB host port, then we can find in log new framebuffer device find.
4. show something: we can use "dd if=/dev/zero of=/dev/fb0 count=1000 bs=768" clean the screen to blank, or "dd if=/dev/urandom of=/dev/fb0 count=1000 bs=768" to show some random image.