lalboard

I got my order of PCBs for the finger and thumb clusters in from jlcpcb today. Exciting! My first time designing and having a PCB made. I'm super happy with the result. Surprisingly, everything seems fine with them so far.

I got one soldered up and attached to a cluster, and was able to send my first key presses with it, with the current in-progress QMK firmware.

I finally managed to hook everything up so that qmk, tinyusb and esp-idf all play nicely together, and managed to get that first glorious "a" key press, from the on-board button on the saola board.

There's still a lot of functionality that doesn't work yet, but I'm super happy that all the USB stuff is working well enough that it's able to enumerate and actually send an HID report on a button press.

I finally got in some parts I had been waiting for from digikey, and was able to throw together a little hand-wired prototype using the new cluster design. I was able to verify there's no light leakage problems between the different keys, and all keys were causing a high enough voltage swing on the phototransistor to trigger a high logic level.

I also realized I had been carrying over the assumption from the previous design that everything would be driven at 5V. But the ESP32's input pins aren't 5V tolerant, so I'll need to switch everything to 3.3V. So I swapped out the LED resistors for a lower value to maintain the same current, and verified again that there's enough of a voltage swing at 3.3V for all the keys.

Incidentally, all those 22g solid copper wires don't make a half-bad mount for the cluster. It's not quite stiff enough, but maybe if the wires were shorter or a bigger gauge. That might be an idea to explore in the future, for a different type of adjustable mount.

QMK seems to be a popular open source keyboard firmware. I've read through their docs a bit, and I think it should mostly support everything that is needed for the lalboard. Namely split keyboards and a robust key mapping mechanism that should be able to support the various mode keys/modes that the lalboard needs.

The only problem is that it doesn't support esp32. I guess I *could* switch to a compatible board/MCU, but a brief search doesn't show anything readily available that is as featureful, available, and cheap as esp32. And there seems to be at least some demand out there for running qmk on an esp32, so I thought I would poke at it bit.

After much gnashing of teeth (and keys), I managed to get a very very hacky proof of concept that compiles and links. This involves

• adding a new esp32 platform to qmk (currently mostly just stubbed out)
• tweaking qmk's build system to build a static library, instead of a full firmware image
• creating a new esp-idf project, that calls into qmk to perform the various processing tasks needed in the main loop. (i.e. something similar to the main loop for the LUFA protocol)
• manually copying that qmk static library to the esp-idf project, and ensuring it gets linked

This is far from an actually functional proof-of-concept, but I think I'm convinced it's at least within the realm of possibility now. I think the next steps will be to more fully implement and integrate the new esp32 functionality in qmk, and ideally figure out some way to link the two builds, to avoid having to build in multiple places and copy stuff around between them.

I doubt something like this would be accepted by the qmk maintainers, since it's essentially using bailing wire and duct tape to smoosh 2 different build systems together. But hopefully it can at least serve as a template for others who want to use qmk on an esp32.

I think I've pretty much finished updating the thumb clusters. I added an .stl and .f3d assembly export for both thumbs, along with an online viewer thingy (links: left, right). And the kicad designs for the PCBs have been updated.

I'm currently waiting on a digikey order for the optical components, to be able to verify the optical performance of the finger and thumb clusters. That order also has some Saola ESP32-S2 boards that I want to play around with, and see if it might be feasible to port the QMK firmware to.

I'm holding off on starting work on the central PCB for now, since that will depend a fair bit on what dev board I end up going with to drive it.

I finally got around to creating a full assembly for a single finger cluster, with all

the various parts in their correct places. The "stls" folder in the github repo should now contain an .stl and an .f3d (fusion archive) for the cluster_assembly part.

I also threw it up on the fusion cloud, where I think it can be viewed by anyone, without logging in. You can check it out here.

I stumbled upon a minor, but nice improvement to the center key mechanism of the finger clusters. The current design is a square peg in a square hole, with a small amount of clearance all around. 

This is fine-ish, but the key post always needed a little bit of clean-up after printing so it can slide in the corresponding hole without binding. There's usually a bit of unevenness around the corners, and especially where the seam is, which can cause the key to rub and bind.

While working on switching over to an actual fabbed pcb, I had rounded the corners of the key post, so the corners wouldn't hit the radiused corners in the milled hole of the pcb.

After I printed some test pieces, I realized that this had an unexpected side-benefit - there's extra clearance between the rounded corner of the post and the still-square corner of the hole. And if the slicer places the seam on the rounded corner, the little "bump" from the seam no longer causes any issues, since there's extra clearance there in the corner. So the center key was able to move nicely in the cluster in an "as-printed" state, without having to add extra clearance (which would also increase undesirable lateral key wobble)

I think I'm close to being done tweaking the design of the main clusters. 

There are some significant changes from the original version

• The photodiodes and LEDs are inserted from the bottom now, so that the PCB can be inserted and removed without having to desolder everything
• The cluster is printed upside down now, and the top surface of the cluster is flush with the top of the key wells, instead of having a thin, flat plate on the bottom of the cluster that the key wells rise up from.
• The keys are wider, to hopefully make them less prone to breakage
• It uses the IR908 LED instead of the IR928 LED, which is a bit thinner, and is the same shape as the PT908 photodiode that is used.
• The adjustable mounting system is now based on using 1/8" x 1/8" x 1/16"  rectangular magnets on the bottom of the cluster, and having the adjustable screw mounts use a 5mm spherical magnet.
  • This gives a fairly firm attachment, while still allowing the angle between the cluster and vertical supports to vary, as the support heights are changed.
  • This also has the advantage that the cluster can be picked up and removed from the supports, while keeping the supports in place, so that the cluster can be placed back down at the same location.
• The bases that the screw supports screw into are now multi-part, and have 2 pairs of 1/8" x 1/8" x 1/16" magnets for more holding power.
  • The magnets are on a separate part that slides down securely over the central "pillar", so that the central pillar can be swapped out (e.g. to adjust the height), while re-using the same magnets.
  • If more friction is needed, to avoid the bases from sliding around laterally, I found that you could rub a bit of beeswax on the bottom magnets. The beeswax provides some slight adhesiveness, while still allowing the supports to be repositioned.
• The screw supports and the bases they screw into now have a very loose fit, that can be easily turned by hand, but with an additional nut that can be tightened down to keep the screw from wiggling or accidentally rotating and changing height.
• The front attachment of the cluster is now a separate part. This allows the attachment point to be higher up, which allows the front of cluster itself to be closer to the base plate. 
  • This is useful especially for the pinky clusters, which are usually the lowest clusters, and typically don't have much room for the screw supports underneath, especially on the front.
  • This also allows that front support part to be removed when switching to a static base down the line, which should be able to hold the cluster with just the 2 back magnets.

I also have a PCB design in the works in kicad, although it needs to be updated a bit with some recent design changes I've made to the cluster.

I think the next steps for now are:   (sorry, another list :p)

• Get some of the new IR908 LEDs, and breadboard up a proof-of-concept of the electronics, to verify that there are no light-leakage issues with the new design.
  • e.g. make sure that the IR light from one key doesn't trigger the photodiode of a different key.
  • There were some changes to the north key's optical component placement in particular that might be problematic. I don't think it will be, but I need to verify that
• Get a saola board to play around with. It doesn't support USB HID out of the box (it still uses a USB<->TTY converter.. WHYYYYYY??), but from what I've read, I think you can just connect a usb micro/C connector up to pins 19 and 20 and get real usb connectivity.
• Update the kicad design for the cluster PCB
  • I'd like to finish up and finalize the thumb and central PCBs before I send it off to be fabbed, so I can just have them all fabbed at once.
• Apply some of the recent tweaks I've made to the finger cluster to the thumb clusters, and get those finalized

I've been thinking about a significant new version of the lalboard for a while now. My goals for the new version include:

• Use actual fabbed PCBs
  • The DIY vinyl-cut "PCBs" were great during the early prototyping phases, but are not suitable for broader use. It's a very fiddly, time consuming process. Using actual PCBs will make the keyboard significantly easier to make, hopefully removing that as a barrier to entry.
• Easier to print
  • Less fiddly custom printing settings needed. It should be mostly printable with stock .2mm layer height print settings.
  • Don't rely on friction for the screw mounts - this requires lots of tweaking of the exact size and printing parameters to get a reasonable amount of friction between the screw and the base.
• More modular
  • Allow the pcb to be removed from the cluster without having to desolder every LED/PT, for ease of maintenance, upgrades, repairs, etc.
    • The LEDs/PTs will be soldered to the PCB first, and then the PCB with all components is inserted onto the bottom of the cluster, and held in place by a screw.
• Add a supported "upgrade path" to a static base.
  • After using my original laboard with the adjustable screw mounts for a while, and getting everything exactly in the positions/angles that I want, I upgraded to a static, non-adjustable mount. However, The existing clusters/pcbs/etc. couldn't really be used with the new static mounts, so I basically had to build a new keyboard from scratch, with all new clusters, etc. So the new version will be designed such that all of the clusters/etc. can be used with either the adjustable screw mounts, or a static mount.
• Parameterized static mount
  • It should be possible to take measurements of an existing screw-mount setup, enter that data and generate a matching static mount.
  • Also, I don't think I ever published the details of the static mount I made for the first version.
  • One option I'm considering is putting fiducial markers on the clusters, and using photogrammetry to determine the relative positions of each cluster. I know meshroom supports CCTag fiducial markers, so it may be possible to, e.g. have a set of special central down keys that can be swapped out in each cluster that have a CCTag printed(??)/applied on them.
• Beefier keys
  • Some of the keys are a bit prone to breaking over time. The worst is the tall, thin mode key on the thumb. But I've broken some of the other thumb keys and even the short normal cluster keys.
  • The cutout for the magnet on the key stem is a particular weak point that is prone to failure, because there's not much material left at the widest point of the cutout.
  • It should be possible to make the keys wider, and maybe a tiny bit thicker, to help reduce failures.
• Use the same form factor of LED as for the photodiode.
  • The LEDs and photodiodes that are used in the design come in 2 slightly different packages (PT908/PT928 and IR908/IR928), with different dimensions. I think there were some supply constraints with which types of which part I could get when I was originally working on the design, but digikey seems to stock both types of both components now.
  • Switching the LED from the thicker package to the thinner package frees up some space allowing the key stem to be wider (see "Beefier keys" point, above).
  • It also simplifies the design a bit, since you only need 1 type of "hole" for the optical components, and things are more symmetrical.
• Use something better/cheaper than the teensy 2.*
  • I love the teensy 2, but it is... a bit long in the tooth. And possibly not long for this world. And the $20+ price point is a bit high by today's standards.
  • I mostly chose it because I had already used it years ago to replace the MCU in my datahand, and knew it would be significantly easier to modify that firmware to work with the lalboard, rather than writing a new firmware from scratch, or adapting another unfamiliar open source firmware to the lalboard.
  • Now that ESP32 has native USB support with the ESP32-S2 variants, I'm currently leaning towards using an ESP32-S2 dev board (e.g. the saola board)
• Firmware that is easier to hack on
  • The existing lalboard firmware is written in hand-coded AVR assembly. That was a ton of fun to write, but is a huge barrier to entry for anyone trying to modify the firmware.
  • I'm currently thinking I'll just write a new firmware from scratch in C for the ESP32-S2, but I'm open to suggestions if there are other open source firmwares out there that may be a good fit. (Update: the current plan now is to modify QMK for use with the esp32-s2)