USB2VGA adapters on XO-1.5 (and XO-1 with F11 images)

Martin Langhoff martin.langhoff at
Fri Jul 9 17:18:47 EDT 2010

On Thu, Jul 8, 2010 at 1:14 PM, Martin Langhoff
<martin.langhoff at> wrote:
> For monitors/projectors that can handle something close to 1200x900 --
> 1152x864, you can use Xinerama instead. Here is an xorg.conf that does
> exactly that:

The Xinerama approach turned out to be a winner in terms of
performance and !bugginess.

Turns out that with a bit of elbow grease we can make it work on
1024x768 which is what most projectors support.

 - yum install xorg-x11-drv-sisvga xorg-x11-server-Xephyr

 - Grab the files from
   olpc-configure goes to /etc/init.d/ , make it executable
   olpc-session goes to /usr/bin/ , make it executable
   xorg-xo1.5-dcon-extmon.conf goes to /etc/X11/

 - Plug the USB2VGA device

 - Reboot & Enjoy

Limitations and notes:

  - Needs to be "switched on" at X startup time. olpc-configure checks
at boot time if sisusbvga is loaded and changes the xorg.conf symlink
if needed. My patch also fixes a longstanding old bug where the
xorg.conf was 'set' in the first boot.

  - The desktop is a little bit smaller. On the XO, the desktop
appears in the top-left corner -- on the external monitor / projector
it fills up the screen perfectly.

  - Icons can appear slightly pixellated. I think this technique may
expose a bug in Sugar and in some activities (ie: TurtleArt) that keep
a copy of rendered SVGs as bitmaps.

  - Performance is acceptable. (We are saturating the USB 2 bandwidth
with the amount of pixels and the bitdepth).

 - The Sugar cursor is back!

 - Video works! No Xv however, so it's not particularly fast.

Patch to olpc-utils is attached -- I haven't tested the spec changes.


 martin.langhoff at
 martin at -- School Server Architect
 - ask interesting questions
 - don't get distracted with shiny stuff  - working code first
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