King44

King44

This is a low profile optical keyboard, based on the KeyChron switches with trackpoint, haptic feedback on layer switches and mod keys, per of the key sculpted key caps.

I still have extra IR/PT parts if anyone needs some.

While I really like the feel of the keys and the position and feel of the trackpoint, the process of getting the protoytpe working was tough to say the least. I am using a T420 trackpoint and the mint key switches, but checking now It would appear that they have been discontinued. :( I have enough for a second keyboard and that is it.

Finding a supply of the IR/PT pair that is small enough was near impossible. In the end I couldn't get them to JLCPCB and had to source a batch directly from the manufacturer and hand solder them. I made the mistake of having many of the parts placed and soldered by JLCPCP. I should have just gotten a stencil to begin with. Hand soldering the IR/PT sensors was tedious and I had many issues. I would not recommend the optical sensors unless you have a stencil and reflow capabilities. Regular soldering temps can damage the lenses.

The second issue was I neglected to consider the rise and fall time of the IR parts. The IR transmitter should ideally always be on, and the receiver probably as well. This though would necessitate using a multiplexer or direct pin reading, but that would mean dropping support for the trackpoint, I2C (haptic + OLED) or both.

I really enjoy the haptic feedback and RGB layers. It makes layer switches more defined and obvious. I have not done too much with it yet, but I am looking forward to playing around with it some more.

The AUTO mouse layer is really nice. It allows me to use the standard thumb keys as mouse buttons, when using the trackpoint. The position of these buttons is much more ergonomic.

Manufacturing

• PCB 1.6mm
• Plate 1.2mm
• Trackpoint
  • harvested from an T420 keyboard
  • trackpoint uses the smaller threaded M2 screws.
    • I could not find a source for these and standard M2 will not fit.
    • My solution was to drill out the holes and tap M2.5 threads with an 8€ drill and tap kit

Issues found in v1.0

• Mounting Plate

  • Tolerances of the key cutouts are too loose.
    • Should be manufactured using with tighter tolerances
    • Looseness of keys can be addressed with a small, thin piece of plastic or paper behind the clear plastic clips to tighten things up
  • Right Mounting Hole for mouse buttons conflict with PCB Plate
  • Power and reset buttons are too thick to be between the mounting plate and PCB
    • Maybe move to next to the mouse buttons
    • or cutout the plate
    • Maybe place on botton to allow for better containment in case
  • MCU is too close to plate, and needs more space
  • Haptic Engine cutout
    • Remove from PCB
    • Increase size on plate
    • Add Mill-Max Pin sockets to base PCB
  • CAP is too high for between boards, move or cut-out from plate
  • trackpoint hole is too small, needs to be 5-5.5mm

• Mouse buttons might be better closer to the keys

  • They need a diode per key, as on any standard mechanical keyboard
  • They need to use the two outside PINS if the logic High model is retained
  • After using AUTO mouse layer, the current locations are definitely less than ergonomic, requiring too much hand movement
  • I plan on working on better solution, potentially with a pivot and you press forward of raise your thumb for mouse buttons.

• trackpoint

  • hole in PCB Plate appears to be too small
  • mounting holes should fit M2.5 to allow the drilled and tapped solution if the smaller M2's can't be found in the future.

• IR Receiver (PT) marking is on the wrong side, which would lead to an upside down disfunctional receiver

  • PT parts have thus been place with the markings opposite the silkscreen.

  • This may actually necessitate a swapping of the pads for manufacturing

  • Need to also review the datasheets to determine the correct orientation for automated manufacturing

• Helios 0xCB

  • Both Hands
    • P1 is actually GND, and needs to be connected as such
    • Switch P1 for P4
    • Power control circuit for touchstick connects touchstick VCC to GND.
      • Current prototype just bypasses the control circuit and always provides VCC to the trackpoint daughter board
  • Right Hand
    • SDA + SCL are incorrect on right hand (left board) and need to be swapped
    • Right ground pin of Helios is not connected to anything
  • Interboard communication for the RP2040 should be done with one wire and the same PIN on both devices
    • Currently there is a software workaround
    • This would free up one PIN for other uses.

• QMK is active LOW, but the logic was built around active high

  • The use of an N-Channel MOSFET in the protoytpe required a custom matrix.c to allow for active HIGH ROW signals
    • a P-Channel MOSFET could resolve this, BUT would require extra components for the mouse buttons, as they also rely on the active HIGH currently
  • Another option would be to rework IR Receiver to pull up instead of down.
    • Currently the IR receiver is needed to pull the circuit down and prevent key presses
  • maybe next time use a input multiplexer, or CPU with more PINS to allow
    • constant on IR LED would use more power, but provide at least 10µs faster response times

• trackpoint

  • Reset CAP wrong -- should connect reset to VCC (NOT GND as it is currently)

• TRRS

  • I stuck with TRRS as I had a nice custom coiled cable from my Span, but I Think it's time to start using USB-C other more common cable
  • That would make it easier to get or make custom cables
  • Remove the short circuit potential when a cable is disconnected while the board is on.

Parts

• BSS138 with pulldown for base SOT23 SMD

  • 2N7002 / C8545

• LED

  • WS2812B-2020 / C965555

• Resistors + Caps

  • RS - 0805 - 220 # lso used for SOT transistors
    • 0805W8F2200T5E / C17557
  • R4.7k - 0805 - 4.7k
    • 0805W8F4701T5E / C17673
  • R100k - 0805 - 100k
    • 0805W8F1003T5E / C149504
  • C2.2u
    • CL21A225KBQNNNE / C377773

• IR Sender

  • AL-S0602IRC-VI-10P9 / C9900048597

• IR Receiver

  • AL-S0602PTB-VI-1016 / C9900048594

• TRRS PJ-320a

  • C2884926

• Power Switch

  • ALPSALPINE SSSS811101 / C109335

• Reset Button

  • EVQPUA02K / C128539

• Buzzer

  • Pimoroni - DRV2605L Linear Actuator

Hardware

• 18x mounting PCB
  • m2 spacer 1.3mm (3D printed ./output/fusion360/spacer_large.3mf)
  • m2 mounting screws 8mm
  • m2 threaded inserts in case
  • m2 screws (8.1mm threaded + head)
    • 1.2mm PCB Plate
    • 1.3mm spacer
    • 1.6mm PCB
    • 2mm Threaded insert
  • m2 6mm for mouse button cap
• 2x mounting trackpoint
  • m2.5 6mm screws
    • 1.6mm PCB
    • 1 mm spacer
    • 1.3mm trackpoint
    • 1.5mm nutFRC0805F2100 TS