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Introduction

Electronics Arduino project, to connect an IBM TrackPoint as an external pointing device via USB.

Features:

  • TrackPoint fully works, incl. buttons.

  • Adjustable sensitivity with potentiometer.

  • Middle button scrolling.

  • An RGB LED cycles, showing how the program loops.

Circuit

Photos of circuit, front and back

For the schematic, see the included EAGLE project.

The PS/2 connection is done with a detachable cable. This allows:

  • testing the Arduino code with an external PS/2 mouse,

  • using the TrackPoint as a PS/2 mouse directly on a computer (didn't get that to work).

Some components were recycled:

  • TrackPoint board: Broken off from the keyboard of an iSeries 1200 (1161-267), my first ThinkPad (bought in 2000).

  • Button switches: Taken from an old Logitech mouse.

  • PS/2 cable: Cut off an old and broken Cherry keyboard.

  • Back metal plate: From the keyboard that provided the TrackPoint board.

  • Front metal plate: Cut from a plate found inside a ThinkPad X41, then drilled.

  • M2 screws: From some ThinkPad.

  • M2 nuts: Insert nuts found in ThinkPad X41 plastic parts.

For cycling the RGB LED, a decade counter is used, partly as an exercise for the author.

Arduino code

See comments at top of .ino file.

Trackpoint PCB

To figure out the pinout of the TrackPoint PCB, the key steps were:

  • I looked at the FFC connecting the ThinkPad's mainboard, the keyboard, and the TrackPoint:

    • Two wires were dimensioned wider: power supply

    • Three lines lead into the keyboard: TrackPoint buttons

  • Using a multimeter and the ThinkPad turned on, I checked the voltage of the power supply wires in the FFC: One is ground, one +5V.

  • I connected the broken off board using individual wires to the ThinkPad. By trial and error, I figured out that in addition to the power supply, three wires are needed (CLK, DATA, RESET).

    Fortunately, the keyboard/TrackPoint FCB receptacles in this ThinkPad are big enough to hold the FFC plus 0.3 mm copper wire.

  • With the TrackPoint board connected to an Arduino, I figured out by trial and error:

    • Which wire is CLK, which one is DATA, and which one is RESET?

    • Which of the button wires is for LEFT, which one for RIGHT, which one for MIDDLE?

TrackPoint PCB soldered to board with 0.3 mm enameled copper wire:

Photo of TrackPoint on board

License

Copyright (C) 2013 Felix E. Klee

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.