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View Full Version : Using the Psychtoolbox to interface with a graphics tablet



Wilson, Andrew
02-22-2009, 09:10 PM
Hi all

I emailed the list about 6 months ago enquiring about solutions for
using a graphics tablet as a 2D motion tracking system. No one had any
solutions but I did get a lot of people asking for anything I found out,
so here's what I found.

Mario Kleiner, the developer for the Psychtoolbox
(http://psychtoolbox.org) coded a quick and dirty solution for me that
allows me to interface with the Wintab driver via Matlab. I've been
using this code with great success for about 6 months. The basic
solution is incorporated into the Psychtoolbox, and entails opening a
'Screen', attaching the tablet to that PTB object, and then pulling data
from the event queue. This queue can buffer about 500ms of data, give or
take, which is useful for recording kinematics while simultaneously
running another process (e.g. stimulus display). You can also pull data
out in real time (the Wacom tablet I have manages 100Hz but I think the
latest ones are good for at least 200Hz).

I've posted a message to the PTB Yahoo forum here:
http://tech.groups.yahoo.com/group/psychtoolbox/message/9182

The files I mention are also hosted on my personal filespace, at least
until May:
https://files.warwick.ac.uk/andrewdwilson/files/TabletDemos.zip (7.5
meg)

This file is larger because it contains some demo Matlab code, the brief
documentation plus a copy of the Wacom tablet driver.

I'm happy to keep updating the documentation with questions and
solutions contributed by other people, although I'm likely to do this
mostly via the PTB forum just because this Matlab mex file requires the
PTB. I heartily recommend the PTB and Matlab for stimulus generation and
data analysis anyway, I've made two full suites of experimental software
using these with great success.

Enjoy, and tell all your friends. There seems to be a lot of dusty
tablets in labs around the world that need to be used, if the response
to my earlier request is anything to go by :) Feel free to contact me
with questions or suggestions for the documentation and if this sees a
lot of use I'll post any updates to the list.

-andrew


***********************
Dr Andrew D. Wilson
Department of Psychology
University of Warwick
Coventry, CV4 7AL
UK

ph: +44/0 24 761 50485
fax: +44/0 24 765 24225