IBM Thinkpad 380ED Keyboard and Trackpoint to USB

[thedalles77]

I have completed a project that converts an IBM Thinkpad 380ED keyboard and trackpoint to a composite USB device.
All of the documentation is at my Github repository https://github.com/thedalles77/USB_Lapt ... ad%20380ED.
The project description and YouTube link is at Hackaday.IO https://hackaday.io/project/171439-ibm- ... int-to-usb
The design challenge was to amplify the voltage from the trackpoint strain gauge resistors (without adding noise) so that the Teensy 3.2 could detect movement with its A to D converter.
I'm not a good enough coder to figure out autocalibration so I setup function keys to allow the user to re-capture the "at-rest" voltage if they notice any cursor drift. So far, there hasn't been any cursor drift but time will tell. The user can also use function keys to adjust the trackpoint sensitivity. The circuit board can be ordered from OSH Park and all components are available from Digikey.

[axur-delmeria]

Excellent work!

Too bad I don't have a 380ED to test this with. I wonder if the Trackpoint part will work with other ancient Thinkpads as well.

[thedalles77]

Yes I believe the trackpoint circuit should work with other older Thinkpads.
Tom Nardi at Hackaday did a writeup called "BREATHING NEW LIFE INTO OLD SCHOOL THINKPAD KEYBOARDS" here https://hackaday.com/2020/05/26/breathi ... keyboards/.

[feklee]

Doesn't the TrackPoint in the 380ED talk PS/2?

A long term project for me is to convert an X41 keyboard to Bluetooth. The Trackpoint in that keyboard speaks PS/2, and with proprietary commands features such as sensitivity can be controlled. Also it supports negative inertia, which I find essential for a good experience.

The TrackPoint on modern day ThinkPad keyboards is unusable to me, too low, and it cannot be used with the classic dome cap. This is the reason why I won't buy another ThinkPad. I am typing this on a 3rd gen X1 Tablet with an external Bluetooth TrackPoint keyboard. Unfortunately, Lenovo decided to discontinue the X1 Tablet series, which also has a nice 3:2 display as compared to the awful wide bezel 16:9 displays in other machines.

[axur-delmeria]

Doesn't the TrackPoint in the 380ED talk PS/2?

Problem is, only the bare sensor is on the keyboard, while the Trackpoint circuitry is on the system board. OP basically built his own Trackpoint controller.

A long term project for me is to convert an X41 keyboard to Bluetooth. The Trackpoint in that keyboard speaks PS/2, and with proprietary commands features such as sensitivity can be controlled. Also it supports negative inertia, which I find essential for a good experience.

IMO the fastest way to support those commands is similar to what OP has done: implement them internally and control them with new keyboard shortcuts. Otherwise, you'll be forced to write your own Bluetooth device driver (because the default Bluetooth HID drivers don't know anything about reverse inertia and other Trackpoint-specific features), or somehow program your device to behave exactly like an existing Thinkpad Bluetooth keyboard so it can use Lenovo's drivers (sounds unimaginably difficult TBH).

[feklee]

Problem is, only the bare sensor is on the keyboard, while the Trackpoint circuitry is on the system board.

Thanks for the explanation. Fortunately, that changed.

IMO the fastest way to support those commands is similar to what OP has done: implement them internally and control them with new keyboard shortcuts.

A few years back, when I originally thought about the design, I added a knob to change sensitivity. Then I decided to use keyboard shortcuts. That was seven years ago, haven’t made any progress since:

• usb-trackpoint Git repo
• ThreadPad (I only want to do the keyboard now.)

Since January, I’m in Hong Kong. Shenzhen, i.e. cheap production is just across the border. So I may give it another go. Also my electronics knowledge has improved.

behave exactly like an existing Thinkpad Bluetooth keyboard

Better not. I use the existing ThinkPad Bluetooth keyboard, and as far as I can tell, it does not use the proprietary commands, which is one reason why it is so terrible.

[axur-delmeria]

A few years back, when I originally thought about the design, I added a knob to change sensitivity. Then I decided to use keyboard shortcuts. That was seven years ago, haven’t made any progress since:

If the knob is easier to implement for you, then move toward than direction. I only suggested the keyboard shortcut route because OP went that way. The Tex Shinobi keyboard used that approach as well: https://deskthority.net/viewtopic.php?f=45&p=464571

An excerpt from that review:

TrackPoint sensitivity adjustment is done through the keyboard by default - Fn plus a number from 1 through 9 adjusts the sensitivity. There's a delay in which the TrackPoint module itself is reset, which I know real PS/2 TrackPoints don't have when the driver adjusts sensitivity, but whatever, it works.

[feklee]

If the knob is easier to implement for you, then move toward than direction.

I already decided for keyboard shortcuts when I designed the ThreadPad. I didn't want to complicate the design by adding a pot.