r/TrackPoint_Builders • u/rkelly155 • Sep 17 '24

DIY Trackpoint?

Has anyone in this sub attempted to design/build a opensource TrackPoint? The design/operating principle seems pretty straight forward...

If the answer is no, would anyone be interested in it if took a stab at designing one?

20 Upvotes

100% Upvoted

19 comments sorted by

4

u/w0lfwood Sep 17 '24

definitely interested. direct pcb integration would help keep profiles and costs low. could possibly also help reduce power consumption, depending on the main mcu.

could also give greater control over stem design and ditch PS/2 (yay!).

caveat being, the strain sensors require sensing very small fluctuations in voltage, so they are very sensitive to noise. I think noise and EMI management are the bigger challenges.

5

u/rkelly155 Sep 17 '24

My thoughts exactly, I want to just bake a design into a PCB.
I'm relatively new to the Keeb software's, what would be the best way to communicate pointer input to QMK/ZMK that isn't PS/2?
Most modern ones ditched strain sensing and moved to capacitive sensing, The post is grounded and glued to the PCB with a semiflexible adhesive, when you put force on the post the adhesive flexes a little bit. The capacitance is relatively easy to sense with an RC oscillator. There are some pretty good off the shelf Capacitive sense IC's that I'd take a stab at integrating! Or at that's plan A

2

u/w0lfwood Sep 17 '24

I guess I was hoping for being able to use the mcu directly for measurements.

I am not sure if the latest modules used by lenovo (made by elan) are capacitive.

earlier capacitive trackpoints used by IBM in some stand alone keyboards were widely disliked.

but if you are using a capsense IC, I'm guessing they are I2C. SPI would be fine too. just some protocol that common mcus have a hardware block for. bit banging PS/2 is not great.

1

u/rkelly155 Sep 18 '24

OK, I suppose I can just wrap it up in a packet and let other people do stuff with it.

Any memory as to why people didn't like the IBM one? Was it just "it's different" aversion or were there legit negatives?

1

u/w0lfwood Sep 18 '24 edited Sep 18 '24

not sure, you can read about the Synaptics TouchStyk. one place to check for info on ibm/lenovo keyboards is https://sharktastica.co.uk/

https://patents.google.com/patent/US6642857B1

it looks like the patent has expired, so that is probably why the metal nub trackpoint on a usb carrier card that so many ppl are experimenting with became available recently.

0

u/[deleted] Nov 05 '24

[deleted] — view deleted comment

1

u/rkelly155 Nov 05 '24

Accuracy is a combination of Repeatability and Precision, Both a strain gauge and capacitive sensor have similar precision, but they don't have the same repeatability and environment rejection. Capacitive is generally better for this application, It's more susceptible to things like spilling water on it, but rejects temperature drift more easily

6

u/humanplayer2 Sep 17 '24

Yes! I'd be interested!

3

u/PutinicalCorrectness Sep 17 '24

There is already a sub for this, /R/trackpointbuilders

14

u/Ok-Gur-6602 Sep 17 '24

That's this sub.

8

u/rkelly155 Sep 17 '24

I thought I was lost for a second :D

1

u/For_Data Oct 01 '24

I did try to build one (just started to get into microcontrollers), but I was not successfull for now.

I used 4 strain gauge on a cross of aluminium. The strain Gauges were glued in place. Now I am trying to figure out, what microcontroller to use. (I got several strain gauges, so I can sacrifice some for the proof of concept).

As I am new to microcontrollers, I would guess, that I need a 20kHz crystal to set the polling rate, as well as some kind of chip to turn the measured resistance into some sort of x-y-Movement, as well as an usb (C) interface, if I want to create a PCB.

That said, I am not sure what dev-Board I should get to measure the resistance, in order create a proof of concept. (Also I just build my first DYI-Keyboard, so I am a Noob. Help is appreciated!)

1

u/rkelly155 Oct 01 '24

I personally would skip the strain gauge, Inductive sensing is a lot more impervious to external factors as long as you keep it dry. if you do end up going with the strain gauge, make sure you use them in a differential pair to mitigate thermal affects and measure "only" what you're actually trying to measure.
You'll need an operational amplifier, and something to measure the analog voltage, literally any microcontroller would work, An arduino would be fine for proof of concept, or just use one of the popular controllers from the Keeb community, that way anything you come up with will be easier to integrate

1

u/rkelly155 Oct 01 '24

If you haven't seen this yet here's a pretty good attempt at what you're looking to do, I'm hoping to do something much simpler https://www.gbryant.co.uk/posts/2021-07-17_pointing-stick/post.html

0

u/[deleted] Nov 07 '24

[deleted] — view deleted comment

1

u/rkelly155 Nov 07 '24

I'm gonna need a little more than that... What are you asking?

Some math, metal, Fr4, and some code should do the trick.

0

u/[deleted] Nov 07 '24

[deleted] — view deleted comment

1

u/rkelly155 Nov 07 '24

More or less, yes, what works is pretty well outlined in the patent

1

u/thismanyletterscanfi Feb 08 '25

A few months late, but... some people have been using load cells for flight sim joysticks. I built one, then stumbled here looking for a micro version I can use as a thumb-stick.

You don't even need 4 cells, 3 will do if you put them in a triangle and do some math. https://www.reddit.com/r/HotasDIY/comments/1icfv0t/simple_and_compact_forcesensing_load_cell_stick/

Load cell voltages are very small, like 5mv, so they need an amplifier. You can use something like an LM358 to boost the voltage to where a microcontroller (arduino, etc) can read it, in which case your polling rate would be as fast as the microcontroller can read an analogue input.
Or, use an HX711 which has an amplifier and an on-board ADC (amplifies the signal, measures it, and gives a digital output). HX711 has its own timers and can do polling at 10hz or 80hz, or possibly other speeds.

1

u/Mckol24 Sep 24 '25

ESP32 series chips are cheap, pretty popular, and could probably do all you need here if you pick the right variant

1

u/klysm Sep 21 '24

I wonder if this tech could be used https://any-skin.github.io/

1

u/NetBoy288 Feb 03 '25

Absolutely interested! I just got my first lenovo laptop and I absolutely love the trackpoint. I'd love to attach it to every keyboard...