Hardware Reference
In-Depth Information
Linux Distributions Without Xorg/X11
OpenELEC makes a build of their XBMC-based Linux OS for the Raspberry Pi, but
it does not use Xorg. Because OpenELEC relies entirely on the VideoCore output
devices, this particular hack will not work on that distribution, unless you rebuild
it entirely from source and enable Xorg support. You'll have the same problem if
you try to use RaspBMC with this hack.
In the
dmesg
output, you're looking for the line that tells you which frame buffer device
the Linux kernel has assigned to the Mimo 720. In the current example, the device
is
/dev/fb1
. It is probably
/dev/fb1
for you as well, unless you have other devices plug-
ged into the Raspberry Pi that show up to the Linux kernel as frame buffers. Just make
a note of this device name, as you will need it to write your Xorg configuration file later.
For the touch panel, look for messages like this in the output of
dmesg
:
input: e2i Technology, Inc. USB Touchpanel as /devices/platform/bcm2708_usb/
usb1/1-1/1-1.3/1-1.3.1/1-1.3.1.3/1-1. 3.1.3:1.0/input/input2
usbcore: registered new interface driver usbtouchscreen
These messages mean that the
usbtouchscreen
driver has been loaded and the e2i
Technology USB Touchpanel in the Mimo 720 has been detected.
Now, look in the
/dev/input/by-id/
directory. You should see a filename that looks
something like:
/dev/input/by-id/usb-e2i_Technology__Inc._USB_Touchpanel_L000000000-event-
if00
Take a note of this filename, which you'll use to identify your touch panel device in the
Xorg configuration file. You use this ID instead of using a
/dev/input/event*
device,
because the ordering of those devices can (and does) change when you add things
like USB mice and keyboards to the bus. Using the touchscreen's unique device iden-
tifier ensures that you always end up with a working X session.
Xorg Configuration
At this point, it is time to start writing your Xorg configuration file. Modern Linux dis-
tributions usually autodetect a working Xorg configuration for the present hardware,
but in the case of the Raspberry Pi, it will result in a working X session for the GPU,
not the Mimo 720. By making your own Xorg configuration file, you'll be overriding the
autodetection and telling the Raspberry Pi Linux distribution to use the Mimo 720 as
the primary graphical display and input device. You can still plug in a USB keyboard
and mouse, and those will be auto-detected and used in addition to the Mimo 720
touchscreen as input sources.
