deskthority

Hi there, it's hard not to notice that many people who like mechanical keyboards also tend to like trackpoint devices integrated into the keyboard. Now, when building a keyboard, one either has to use hard-to-get and expensive new trackpoints sold specifically for that purpose, or chooses the option of sacrificing one of those many ThinkPad keyboards with missing key caps out on ebay for the price of a cup of coffee. I haven't been able to find a database of the various models of the latter, along with its electrical and mechanical requirements, therefore I opened this topic. The idea is that we gather as many as possible of the various models of ThinkPoint, along with models they appeared in, so that when shopping for keyboards, we have a better chance of finding the one we're looking for.

For a start, this is the first one I came across: According to the seller, it's from a keyboard for the ThinkPad A22p, also compatible with A20, A21, A22 (none of which I can confirm). I think this is a common type, since it also appears in Suka's DIY keyboards (look at his thread for the electrical pinout). As far as mounting is concerned, here are my measurements:

- The trackpoint reaches through an 8mm hole in the keyboard "plate" from underneath.
- On the original keyboard, there is a space of 2mm between the bottom of the keyboard plate and the top of the PCB, so that the black triangular part (whose top is some kind of foam or rubber) is pushed against the keyboard plate when installed.
- Two of the mounting holes (ø2.5mm) are in a line with the trackpoint, at a distance of 10.5mm to either side of it.
- The other two (also ø2.5mm) are 19mm apart, 8mm across from the trackpoint (down in the photo).

ħ

Here's the second one: It's from a chiclet keyboard, apparently for the W530, T530, T430, T430s, X230, therefore of newer date than the previous one. It's still based on the TPM754, so I guess it has the same electronic interface (except maybe the pinout).

Here are measurements:

- The hole in the keyboard plate is still ø8mm.
- This time, the device was mounted using two screws (apparently M2, thread pitch unknown) from the top of the keyboard, using the threaded holes on either side of the trackpoint. Their distance is 19mm.
- There are four more threaded holes, same thread, 20.9mm apart horizontally (in photo), about 3.5mm and 9.5mm from line of the other two.
- The metal plate with the threaded holes is designed to be in contact with the keyboard plate, no spacer required this time.

That's what I have for now.

ħ

Great idea. Here's the TP from the IBM SpaceSaver II:







I believe there's a picture posted on DT by webwit with some interesting TP modules that I'd like to hear more about too.

hbar wrote: I haven't been able to find a database of the various models of the latter, along with its electrical and mechanical requirements, therefore I opened this topic.

The closest I could find to a "database" is on the ThinkWiki at: http://www.thinkwiki.org/wiki/TrackPoint
That doesn't include "its electrical and mechanical requirements", but might be is a good reference for identifying which laptop contains which variant of TrackPoint (pointing-stick) hardware. I cannot vouch for its accuracy.

-bg

bg, that page only tells us which generation a device belongs to, not its actual physical layout and pinout. The two ThinkPad trackpoints I posted, for instance, are both type IV. In fact, of all the ThinkPads I've ever used, only the oldest one (365XD) had a type III, all others were of type IV.

Here are some rubbers I found: Anyone has any idea where to source tensometers that could be used to build these? Are these all custom, or available as standard parts?
What's the alloy? Can these be machined, perhaps?

Oh, and a Toshiba Libretto one, cross-post from GH: