I just got the pen working on my Stylistic 1200 yesterday. I'm running Debian (sid), kernel 2.4.18 (stock 2.4 Debian install kernel; I don't think the version should matter much), XFree86 4.3, xdm 4.3.0, icewm 1.2.16.
First, you will need to add the following lines to some sort of startup script (I put them near the bottom of /etc/init.d/setserial, which may not be present in your Linux distribution):
/bin/setserial /dev/ttyS3 IRQ 15 baud_base 115200 port 0xfce8
/bin/setserial /dev/ttyS3 autoconfig
You can also run those by hand (as root) before doing your testing. Once you've run those, try doing this:
cat /dev/ttyS3
Then move the pen around the screen. If you see a bunch of garbage displayed on the screen when you move the pen, then your serial port settings are (most likely) correct.
It took a lot of tweaking /etc/X11/XF86Config-4 and restarting X, but I finally got the pen driver to work. Here are the important bits from my XF86Config-4:
Section "InputDevice"
Identifier "mouse0"
Driver "fpit"
Option "CorePointer"
Option "SendCoreEvents" "true"
Option "AlwaysCore" "on"
Option "Device" "/dev/ttyS3"
Option "BaudRate" "19200"
Option "MaximumXPosition" "6385"
Option "MaximumYPosition" "4950"
Option "MinimumXPosition" "110"
Option "MinimumYPosition" "250"
Option "InvertY"
EndSection
Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "mouse0"
InputDevice "Configured Mouse"
# InputDevice "Generic Mouse"
EndSection
The MaximumXPosition, MaximumYPosition, MinimumXPosition, and MinimumYPosition values are used to calibrate the pen with respect to the touchscreen geometry. Those are the values that worked on mine (and I imagine should work on any Stylistic 1200, but Your Mileage May Vary). Again, there was a lot of trial-and-error work... adjust values, restart x, test, rinse, repeat.
I'm still trying to get the second button on my pen to work (currently only the button on the tip of the pen works), but I don't think that should be too difficult. The FPIT driver is included with XFree86 (at least in the Debian package), and there's a somewhat helpful man page. Let me know whether this information works for you. I'll post more info if/when I get the second button working.
