Revision as of 13:45, 23 January 2013

On this page you will find usefull informations to have a working Linux Framebuffer on your board.

Introduction

Linux Framebuffer is the lowest level (standardized) API for userspace programs to access video capabilities of the system you're running on. It allows you to directly "draw" your graphics in the video memory. Some higher level librairies can be put on top of the Framebuffer for more portability: SDL, Qt/Embedded, GTK, DirectFB, etc...

Kernel configuration

Note: Framebuffer is already configured (for Sharp LQ043 LCD on APF9328 and for Chimei LW700 on APF27/APF51) in standard/default Armadeus kernel image.

Following instructions are only given as references or if you want to change the default LCD:

• launch Linux kernel configuration:

 [armadeus]$ make linux-menuconfig

• activates:

 Device Drivers  
    ---> Character devices  ---> 
        [*] Virtual terminal
        [*]   Support for console on virtual terminal

• on APF9328 activates:

 Device Drivers  
    ---> Graphics support  
        <*> Support for frame buffer devices  --->
             <*>   Motorola i.MX LCD support

• on APF27 activates:

 Device Drivers  
    ---> Graphics support  
        <*> MXC Framebuffer support (Freescale driver)

• and choose your LCD in:

 Device Drivers  
    ---> Graphics support  
        ---> LCD Panel (xxxx)  --->

• activates:

 Device Drivers  
    ---> Graphics support  
        ---> Console display driver support
            <*> Framebuffer Console support

• deactivates VGA stuff & add some fonts, then choose Armadeus boot logo:

 Device Drivers  ---> 
    Graphics support  ---> 
        [*] Bootup logo
        [*]   224-color Armadeus Linux logo

• recompiles the kernel:

 [armadeus]$ make linux26

• reflash kernel image on your board and enjoy ! (you should see Linux logo on screen at startup)

Userland

• Framebuffer device can be accessed with /dev/fb0.

• You can activate some tools from the Buildroot's menuconfig:

 $ make menuconfig

 Package Selection for the target
     ...
     Graphic libraries and applications (graphic/text)  ---> 
     ...
         [*] fbgrab
         [*] fbtest
         [*] fbv
     ...
        ---> Graphic libraries and applications (graphic/text)  
            ---> fbset/fbv/fbgrab

Note: As explain on LinuxInstall page, to compile fbtest, libnetpbm10-dev must be installed in your host system

• For example to grab a snapshot of the framebuffer:

# fbgrab /tmp/snapshot.png

• For example to display an image using standard image file formats PNG, GIF...:

# fbv myimage.png

Tips

• To stop blinking cursor:

 # echo 0 > /sys/class/graphics/fbcon/cursor_blink

also possible at boot time (with 3.x recent kernels):

BIOS> setenv extrabootargs vt.global_cursor_default=0

• To make it blinking again:

 # echo 1 > /sys/class/graphics/fbcon/cursor_blink

• To grab a screenshot of a running Framebuffer application, use FBGrab
• To enter in Framebuffer sleep mode:

 # echo 1 > /sys/class/graphics/fb0/blank

• To leave Framebuffer sleep power mode:

 # echo 0 > /sys/class/graphics/fb0/blank

• To set "sleep mode"/screensaver entering time (where X is a time in minute; 0 = never):

 # echo -e '\033[9;X]' > /dev/tty1    (from serial console)

or

 # echo -e '\033[9;X]'    (from framebuffer console)

or to set it at each boot, use /etc/inittab:

 tty1::sysinit:echo -e '\033[9;X]'

Other usefull ESC sequences

• To (definitly) hide cursor:

 # echo -e '\033[?17;0;0c' > /dev/tty1    (from serial console)

or

 # echo -e '\033[?17;0;0c'    (from framebuffer console)

• inverse screen on:

 # echo -e '\033[?5h' > /dev/tty1

• inverse screen off:

 # echo -e '\033[?5l' > /dev/tty1

Links

• How to change the Linux boot logo
• How to configure soft cursor
• http://linux-fbdev.sourceforge.net/
• Linux console ESC sequences
• http://directfb.org/
• Blackfin wiki page on the subject