TrackPoints

trackpoint_on_kbd.jpgtrackpoint.jpg

A TrackPoint connect as a PS2 mouse. you just have to wire it up correctly. (*)
2._Closeup.JPG
(*) the above picture is missing the reset pin... the edgemost pin should be held high for a few moments upon power up.

I got my TrackPoints from old laptop keyboards. on one particular brand it is possible to separate the strain gauge from the circuitry:
the IBM part number is 08K4959, the Fru number is 08K4988.
TrackPoint_Separable.JPG

separating, trimming the circuit board and glueing a rumble unit to the base gives:
Rumble.JPG
and the circuitry can be tidied thus:
TP_Board.JPG

the problem is that most new computers do not have a PS2 port, and even if they do, that's not much good because I want to use several.

so i had to use a MicroController

in case you're wondering "why doesn't he just run each one through a PS2 -> USB converter, and separate the mouse signals with a bit of nifty windows programming?" the answer is that these converters report as a generic USB mouse. I need to send a custom commands to these TrackPoints, because I'm interested in the raw-pressure values - especially the vertical pressure. it is impossible to send these commands through converters; these commands are not part of the PS 2 protocol - they are particular to the TrackPoint. but kudos if you thought of it. thanks to Dave for finally figuring it out.