  Linux Touch Screen HOWTO
  Christoph Baumann, cgb@debian.org
  Oct 24, 2000

  This document describes how to set up a touch screen input device
  under XFree86. As the author had only the opportunity to work with
  devices from EloTouch(R) and MicroTouch(R) this HOWTO is rather spe­
  cific for these devices.
  ______________________________________________________________________

  Table of Contents


  1. Which sort of devices are described here?

  2. How to configure the device

  3. Activating the device

  4. Using touch screen and mouse in parallel

  5. Suggested reading



  ______________________________________________________________________

  1.  Which sort of devices are described here?

  This HOWTO concentrates on devices connected via the serial port i.e.
  /dev/ttyS0 or /dev/ttyS1.

  2.  How to configure the device

  Touch screen devices are configured in the Xinput section in the
  XF86Config file (mostly /etc/X11/XF86Config or /etc/XF86Config).  At
  first verify that the device driver modules exist. They are located in
  /usr/X11R6/lib/modules/ (the modules for the above mentioned devices
  are xf86Elo.so and xf86MuTouch.so). Now have a look into XF86Config.
  There should be a section looking like this:


  Section "Files"
  ...
  ModulePath "/usr/X11R6/lib/modules"
  ...
  EndSection



  To get the module loaded by the X server there has to be a section
  like this:


  Section "Module"
  Load "xf86Elo.so"
  EndSection



  Now the more tricky part. X needs to know some parameters about the
  device.  The section for this looks like this (see "man XF86Config"
  for more details):



  Section "Xinput"
   SubSection "Elographics"
  #the entry for a MicroTouch device would be SubSection "MicrotouchFinger"
    Port "/dev/ttyS1" # for a device at serial port 2
    DeviceName "TouchScreen" #could be any unambiguous name
    MinimumXPosition 300
    MaximumXPosition 3700
    MinimumYPosition 300
    MaximumYPosition 3700
    UntouchDelay 10 #not supported with MuTouch
    ReportDelay 10  #not supported with MuTouch
    AlwaysCore #activates the device on startup
   EndSubSection
  EndSection



  The values for the entries MinimumXPosition etc. are of course
  specific for the setup of the hardware (i.e. depend on the position of
  the touch screen relative to the monitor). The values determine where
  the points (0,0) and (xmax,ymax) on your monitor (xmax and ymax depend
  on the resolution chosen for the Xserver, such as 1024x768) are mapped
  on the touch screen.  The device driver reads these values and
  interpolishes the other coordinates.  For illustration:


   --------------touch screen area-----------------
   I                                              I
   I  ########visible monitor area##############  I
   I  #x                                       #  I
   I  # (0,0)                                  #  I
   I  # (MinimumXPosition,MinimumYPosition)    #  I
   I  #                                        #  I
   I  #                                        #  I
   I  #                                        #  I
   I  #                                        #  I
   I  #                                        #  I
   I  #                                        #  I
   I  #                                        #  I
   I  #     (MaximumXPosition,MaximumYPosition)#  I
   I  #                             (xmax,ymax)#  I
   I  #                                       x#  I
   I  ##########################################  I
   I                                              I
   ------------------------------------------------



  This mapping can be done by trial and error or by reading the raw
  output of the device (needs some serial port programming, see "The
  Linux Serial Programming HOWTO"). For the types EloTouch and
  MicroTouch exists a rudimentary calibration tool (written by the
  author of this document, it can be found at
  ftp://metalab.unc.edu/pub/linux/X11/xutils/touchcal-0.1.tar.gz
  <ftp://metalab.unc.edu/pub/linux/X11/xutils/touchcal-0.1.tar.gz>).

  3.  Activating the device

  After starting X, type in an Xterminal the command

  xsetpointer <devicename>

  where<devicename> is the name defined in XF86Config with the line
  DeviceName ".....", in this example it would be TouchScreen.


  To get the device working on startup use the AlwaysCore option in the
  touch screen section (see above)

  4.  Using touch screen and mouse in parallel

  To use the touch screen and a mouse in parallel you need to enter the
  mouse specs in the Xinput-section. This definitions should be the same
  as in the Pointer-section. The following example is for a PS/2-mouse:

  Section "Xinput"
     SubSection "Mouse"
        Protocol "PS/2"
        Port "/dev/mouse" #could also be /dev/psaux
        DeviceName "Mouse"
        AlwaysCore
     EndSubSection
  ...
  EndSection


  Several people pointed this out, especially the usage of the
  AlwaysCore option. Thanks to them all.

  5.  Suggested reading


  ·  Manpage for XF86Config

  ·  http://www.elotouch.com/Support/linux.asp
     <http://www.elotouch.com/Support/linux.asp>

  ·  http://www.hof-berlin.de/tablet/tablet.html <http://www.hof-
     berlin.de/tablet/tablet.html> (Thanks to Christer Olofsson for
     sending me this URL)

  ·  The manual shipped with your touch screen :-)



