Notices by makkin thing (gbrnt@mastodon.technology)

In terms of simplifying assembly, it looks like IBM eventually moved to capacitive sensing instead of resistive. I'm not entirely clear on how it would work but I have an idea.

It's probably worth trying it out! Should be able to do some rudimentary capacitive sensing with one of the Arduinos I have lying around.

So after replacing the pointing stick's Y-axis strain gauges, it's a bit stiffer than the X axis but more usable than a broken axis.

The pointing stick is already pretty usable on my linux desktop. Weirdly, when I transfer my USB hub to my work Windows laptop, the cursor starts drifting. Really not sure why that happens. Maybe it's something to do with grounding, or maybe it's something to do with Windows.

I've been trying and failing to correct the drift in the pointing stick. It seemed like it might be a good idea to visualise the jitter in the measurement.

This is a heatmap of the X and Y changes from a baseline over a ~15 minute period of not using the pointing stick.

It looks like a deadzone with a radius of 15 should ignore most of the noise. I forgot to include a footprint to add a low-pass filter, but that definitely seems like a good idea.

Mutilating a keyboard and keycaps for the next prototype on the pointing stick project.

Drilling a hole for the pointing stick only cut 2 traces so it should be easy enough to fix with a couple of mod wires.

My new cheap hot air soldering station arrived, along with some solder paste that turned out to be leaded (I forgot to check). Tried it out and holy shit it's like magic! This is a game changer for micro USB connectors.

I tried it out on a pointing stick PCB and it's a big improvement over my dodgy hand soldering. It also saved a board I had written off because it was too much of a pain to fix the USB connector.

Made a bit more progress on the pointing stick project before I realised I only have one strain gauge left. I did order more but the order got cancelled.

The mod wires went fairly smoothly, although I still hate stripping magnet wire. Haven't checked that they work - that would be a good idea because this mod is likely to be permanently glued on. Perhaps I should use hot glue to be safe.

I also printed and heavily ground away at a new mount for strain gauges.

Accidentally made a new thread for the pointing stick, so here's the old one: https://mastodon.technology/@gbrnt/105906955241870768

Ah yeah, that'd do it

I'm still working on the code for the pointing stick, but it looks like I've managed to (physically) break the Y-axis. That was the one with a dodgy strain gauge that I just put some hot glue over.

Hopefully if I lift off the pads I can just glue another gauge on top and not lose too much sensitivity.

Programmed some keys on my keyboard to be mouse buttons and the pointing stick is now usable!

It's a little bit too high - I keep hitting it while typing H and I just found out that I type B with my right hand instead of my left. It would be easier not to hit it if the keyboard had a slight split.

With this longer stem on the pointing stick I am noticing drift starting to happen. That gives me a reason to look at correcting it.

Today I'll design a little nub for the top of the stick!

Unfortunately I found out that there's something wrong with the pointing stick board I soldered with the hot air station. I can't burn the Arduino bootloader on it with a setup that works for the first one I put together. Can't see anything wrong with it, so it might just be that I killed the chip while soldering it :(

Major progress on the pointing stick project today! I actually managed to build it into a keyboard!

Started by redesigning the strain gauge mount to clear the keycaps, then printed and assembled it. That went smoothly but took a while.

It turned out the keys I bought are plate mount so they lack the little pegs that go into the PCB! But they'll do - this is just a prototype, the keys aren't the important thing here.

Initial testing feels good but it's late so I'll try it tomorrow!

Turns out the strain gauge I replaced probably wasn't the one that had an intermittent connection - replacing the top gauge in the photo didn't fix the problem of the pointer jumping around.

If you look closely you can see the bottom one's left contact has broken off after I poked it.

Basically these strain gauges are not something that'll work for a device in production. The gauges themselves are fine, but the heat of soldering messes with the pads and it's a fiddly manual process.

Oops, turns out my polyester resin keycaps don't like being removed with a keycap puller! The resin is too brittle :(

Anyway, I already wanted to use epoxy or polyurethane. Hopefully they'll be a bit tougher.

The keycaps should be fully cured now! They feel a little tacky when you put them against a hard surface - not sure if that's just what polyester is like.

The bottom corners weren't quite filled but the caps feel nice! Weirdly they had the texture from the original when I demoulded at 2 days, but lost it during the rest of the cure.

The long cure time and the lingering styrene smell are making me want to switch to epoxy/urethane before I do any more casting.

I tried some casting! These keycaps haven't turned out perfect - the corners didn't have enough resin, not sure why. But once they're fully cured in a week they'll be cool to try out!

The moulds I've made have turned out really well but I have a long way to go with the casting. I think it would help to change to an epoxy with a mix ratio closer to 1:1, so there's not a really tiny amount of hardener to measure out.

@ekaitz_zarraga Yeah, total overkill! I'm just familiar with it because I used it on my keyboard. For a "proper" version I'll use a smaller/cheaper microcontroller.

The prototype #trackpoint actually works surprisingly well! It has no acceleration or anything and it's a bit slow, but once I added a dead zone it's already fairly usable.

Not sure if you can see it in the video once it's compressed, but it's moving the pointer.

Great, I've somehow managed to (temporarily) brick both that Arduino and my backup one. Seems like the Mouse.h stops them properly connecting to my computer over USB, even without actually using anything from it.

Once my strain gauges arrived I built a version 2 of the strain gauge trackpoint, with both axes hooked up.

I've attached all 4 strain gauges to allow for temperature compensation later, but for now this seems to be ok. It's a lot more sensitive with the gauges superglued to the thing! Before they were secured with double sided tape, which must have absorbed some of the strain.