XO-1/Touchpad/Issues

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Occasionally, a laptop's touchpad will behave abnormally. This behavior includes the pointer jumping to a corner of the screen, or moving wildly. On current software (release 8.2 or better, consider upgrading!), the touchpad will be automatically recalibrated when this happens. You should hold your fingers away from the touchpad when this happens.

A recalibration of the touchpad can be manually invoked using the "four-finger salute" (Escape + Frame + Right Arrow + Fn, with Fn pressed last). Work-arounds in extreme cases include using a common USB mouse with the laptop.

If using older software/hardware

While not all issues have been resolved in 2009, especially when using older software/hardware from 2007 and earlier in 2008, three touchpad issues stood out:

The pointer jumps to the bottom-right corner of the screen

This can happen right after you touch the touchpad. Rebooting often helps (see <trac>2804</trac>).

The four-finger salute (Escape + Frame + Right Arrow + Fn, with Fn pressed last) usually fixes this.

The pointer moves around by itself

Instead of reliably following your finger, the pointer can move around on its own, sometimes when a hand is close to it. The four-finger salute (Escape + Frame + Right Arrow + Fn, with Fn pressed last) usually fixes this. Automatic recalibration on reboot may also fix the problem.

Mouse moves mostly vertically

If the touchpad works fine vertically but doesn't function horizontally (<trac>5575</trac>), it is likely due to damaged touchpad wiring. This was corrected and is very rarely seen in recently produced laptops.

Reducing the impact

In addition to forcing a recalibration yourself, using the four-finger salute, the kernel will sometimes notice a recalibration is necessary, and commence the process automatically. In releases 8.2 and later it's possible to adjust some parameters which affect how, and how quickly, the kernel will tell the touchpad to recalibrate. This script will sets the most pertinent of the mouse driver parameters to values that make the calibration take less time -- meaning your fingers don't have to be off the pad as long before you can start using it again. Unfortunately, this needs to be run as root (sudo), so you can't just put it into a .xsession or .bashrc file.

#!/bin/sh

# the available touchpad parameters (the ones pertinent to recalibration)
# are as follows:
#
#    recalib_delta:  packets containing a delta this large will
#       cause a recalibration. (int)
#    jumpy_delay:  delay (ms) before recal after jumpiness detected (int)
#    spew_delay:  delay (ms) before recal after packet spew detected (int)
#    recal_guard_time:  interval (ms) during which recal will be
#       restarted if packet received (int)
#    post_interrupt_delay:  delay (ms) before recal after recal
#       interrupt detected (int)
#    autorecal:  enable recalibration in the driver? (int)
#


p=/sys/module/psmouse/parameters

if [ $(whoami) != root ]
then
    echo must be root >&2
    exit 1
fi


( echo Before: ; grep ^ $p/* ) >/tmp/cur_psmouse_params

if [ "$1" = show ]
then
        cat /tmp/cur_psmouse_params
        exit
fi

echo Setting mouse parameters:

# all values in milliseconds

echo 200 >$p/jumpy_delay
echo 200 >$p/spew_delay
echo 400 >$p/recal_guard_time
echo 100 >$p/post_interrupt_delay

( echo After: ; grep ^ $p/* ) | diff /tmp/cur_psmouse_params -

exit

Large Jump Logging Technique

The following highly technical sequence is for developers with build 802 on XO-1 C2 units, which lets them capture touchpad events in more detail ... it can be deployed to children with the instruction "when the touchpad goes nuts, please press the key to the left of the frame key, this will record data that we will use to analyse the problem, and you'll hear a short beep when it is done.".

# make a script that records the kernel messages to a file

cat << EOF > /usr/local/bin/grab-touchpad-log
#!/bin/sh
dmesg | gzip - > /home/olpc/dmesg.\`date +%s\`.gz
speaker-test --test=sine --frequency=800 &
PID=\$!
sleep 0.1
kill \$PID
EOF

chmod +x /usr/local/bin/grab-touchpad-log

# configure kernel to record touchpad events on next boot and now
echo 'echo 1 > /sys/module/psmouse/parameters/tpdebug' >> /etc/rc.local
echo 1 > /sys/module/psmouse/parameters/tpdebug

# set up the matchbox window manager to run the script when the key
# to the left of the frame key is hit
echo "XF86Messenger=!/usr/local/bin/grab-touchpad-log" \
    >> /usr/share/sugar/data/kbdconfig