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Up! Aldi's low-cost digitiser tablet in Linux · Dec 13, 12:32 AM

Drawing is fun but even the greatest artist will struggle with a mouse or a laptop touchpad. A better device would be some kind of tablet, but they can be expensive. So I had been looking out for a cheap one for some time and at last Aldi came up with the Medion MD 85637. The next challenge was to get it working in Linux.

The tablet has been supported in the Linux kernel since the 2.6.21 or so. That means that the kernel will recognise it but not necessarily do anything with it. The linux USB device database on the ‘net says it uses the wacom driver.

For Fedora 8 I had to add some configuration in the form of udev rules to make the device available to users: I made a 20-medion-MD85637.rules file in /etc/udev/rules.d

KERNEL=="event*", SYSFS{idProduct}=="0031", 
SYSFS{idVendor}=="172f", SYMLINK+="input/tablet"

The product and vendor IDs match those seen in /proc/bus/input/devices. The symlink will appear as /dev/input/tablet.

At this point it’s possible to plug in the device and see some pointer movement on the screen – but the position will be strange as the co-ordinates for the tablet are not yet known. To fix this we need some way to spy on the numbers that the tablet is emitting – there is already such a utility for wacom devices – wacdump. Running it and moving the pointer around lets us see the limits of the tablet (0,0) to (10000,6250)

The next step is to add the device to xorg.conf so it will be recognised as a pointer device and make the mouse move. This involves adding an entry like this:

Section "InputDevice"
         Identifier "WALTOP Slim Tablet"
         Driver "wacom"
         Option "Device" "/dev/input/tablet"
         Option "Type"   "stylus"
         Option "USB"    "on"
         Option  "TopX"          "0"
         Option  "TopY"          "0"
         Option  "BottomX"       "10000"
         Option  "BottomY"       "6250"
         Option  "MaxX"          "10000"
         Option  "MaxY"          "6250"
 EndSection

The ServerLayout section of xorg.conf needs an addition too:

        InputDevice     "WALTOP Slim Tablet" "AlwaysCore"

The details were mostly copied from examples on the ‘net.

At this point the tablet is almost completely configured – apart from the best feature! Go into the Gimp and navigate through the preferences to input device configuration. Add in the tablet and enable it, and the joy of pressure sensitive drawing tools will be available. You’ll never want to draw with a mouse again!

  1. I’m interested in this post, I just bought one, but it doesn’t work for me, I’m using Ubuntu Gutsy… I got the pointer, but it acts funny, the pressure is not OK and doesn’t appear in Gimp, what can I do ?


    — flarre    Feb 24, 01:43 AM    #

  2. Try add this line:
    Option “Mode” “absolute”
    ..into the “InputDevice” Section

    Regarding the pressure issue, follow this link:
    https://help.ubuntu.com/community/TabletSetupGIMP


    — trivius    Jun 26, 01:09 PM    #

  3. Hi, thanks for the guide – I got this working in Ubuntu but it doesn’t work in Gentoo because of all the stupid HAL stuff overriding xorg.conf. If I figure out how to write a hal config for it I’ll post it here, might be of help to someone else…


    — ant    Jul 1, 02:19 AM    #

  4. After scouring the net for days I’ve figured out how to get this to work with HAL config. So here you have it:

    1. You need XServer 1.5 (or a prerelease) or it won’t read the config at all!
    2. Make a file named /etc/hal/fdi/policy/10-tablet.fdi (or whatever you prefer), and where you’d have an option in xorg.conf, use: «merge key=“input.x11_options.{option name}” type=“string“»{option value}«/merge»
    (Or just use mine)
    3. ???
    4. Tablet!

    Of course, you could just disable the AutoAddDevices option in xorg.conf and use the original method. I did it this way because configuring my keyboard manually was a nightmare.


    — ant    Jul 2, 07:31 PM    #

  5. Just installed a MD85637 tablet on a desktop running Ubuntu 8.04. Some interference between the PS2 mouse and the pen. Only change I have made was to change InputDevice “WALTOP Slim Tablet” “AlwaysCore” to InputDevice “WALTOP Slim Tablet” “SendCoreEvents”. This seems to have stopped the interference. Using GIMP the pen works great and is pressure sensitive. Drawing lags behind the pen but catches up when the pen is stationary.


    — david    Aug 1, 07:13 AM    #
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