Hi

Recently I bought a Seiko InkLink device. It is a pen input device that uses a
special pen, together with a paper pad clip that incorporates two ultrasound
sensors to pick up signals from the pen. This allows the movements of the pen
to be tracked with reasonable accuracy. The clip can be linked to a
desktop/laptop via a USB link, or by a special additional component (supplied
with the device) that supports an IrDA link. This is intended for a PDA. 

Software support comes with the product only for Windows. Unfortunately, I
didn't find the software to be very functional so wanted to write some of my
own. There are no Linux drivers. However, Linux recognises the device as a USB
HID, so it is possible to read the input messages from the device. After some
careful playing around I have managed to make enough sense of the input
messages to build a simple application that allows the pen to draw to a window
in Linux. 

There are lots of limitations with the software: the device drops messages
every so often (it sends in groups of 8 at a time, but loses 1 of these about
15% of the time, I reckon) and also fails to give one of the two position
measurements about 50% of the time. Currently the software simply ignores
sequences that are missing values, but I think it could do better (there might
be some error correction stuff in the parts of the messages I do not interpret
and it would also be possible to use some sort of "interial" model of the pen
movement to compensate for the missing measurements). In addition, the
application is very basic: it allows drawing from the pen, supports export to
xfig format with some attempts at recognition of lines and circles (still
pretty rudimentary), clearing of the window and it also allows a backdrop to
be installed into the window. This latter I have used to experiment with
writing notes onto a copy of a page or for tracing pictures. There is scope
for considerable development! I have been looking at open source handwriting
recognition software with the intention of integrating that to allow the pen
to be used for note taking.

I do not know anything about writing device drivers, so I don't have much idea
about whether the code could be used to help in the construction of a driver
that would allow the pen to be used as an input device in existing
applications (gimp, say). 

Anyway, if anyone is interested in seeing what I have or in helping to extend
it in any way, please contact me (derek at cis.strath.ac.uk). If anyone has
any suggestions about alternative (or better) forums for me to advertise this
on, please let me know.

Cheers

Derek





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