Darknight: DIY 60% Split Keyboard

Ergonomic Design - Layout - Parts - Tools - Construction - Updates

Ergonomic Design

• 60% keyboard for programmers, especially vim users
• Symmetric ortholinear / matrix layout
• Split and tentable
• Tenting angle quickly adjustable by moving the tenting racks inwards or outwards
• Mild contour to adapt to finger lengths, with z-staggering and cherry-profile keycaps

Layout

• Fn key is at the home position of left thumb, which makes cursor moving keys on the right half easily accessible.
• Ctrl and Fn keys are dual-role modifiers. When tapped, they produce Escape, Enter and Backspace instead. The only downside is that they can’t auto-repeat because they are modifiers when pressed and held. (Hint: Use Ctrl-Backspace to delete words.)
• Left-click and right-click are at the bottom row of the left half. One can move the mouse with right hand and click on the keyboard with left hand.
• Brackets and Backslash are at the bottom row of the right half. Single-quote is right above Enter. These changes allow the right half to have only 6 columns and mirror the left half.
• The blue keys are the home keys of fingers at rest.

Parts

• 6 3D-printed case pieces and 2 tenting racks
  • Front piece, back piece and chip cover for each case
  • 8 M2x16 screws and 8 M2 nuts for assembling the cases
• 60 Gateron red switches (or any Cherry MX compatible switches), plate mounted
• 60 Blank PBT keycaps from a 120-piece set
  • 60 O-rings for dampening
• One Teensy 3.2 or Teensy LC as controller
• For handwired matrix
  • 22 AWG 6-color stranded hook-up wires
  • One 0.25mm copper sheet, 6x6 inches
  • 60 1N4148 diodes
• One USB-C gen 2 cable (with plugs cut off) for connecting halves. See issue #1.
• One USB mini cable for connecting the keyboard to computer

Tools

• 3D printer
• Soldering iron
• Tweezers
• Wire stripper
• Heavy duty scissors
• Knife
• Nails and hammer
• Filer
• Multimeter

Construction

Printing cases and tenting racks: 17 hours

• Print cases: 16 hours with PLA and 12 hours with ABS
• Print tenting racks: 2 hours with PLA and 1.5 hours with ABS
• Print chip covers: 10 minutes

3D models in STL format as well as the OpenSCAD file producing them are in models directory. I use FlashPrint for FlashForge Creator Pro to convert STL files to X3G files before printing them from a SD card.

There are three choices of racks. rack-rigid.stl is quick to print and rigid for high tenting angle. rack-curvy.stl is good looking but not rigid. rack-blend.stl is good looking and rigid.

Installing switches and keycaps: 20 minutes

• Install switches: 10 minutes
• Orient switches: pins are at the top half
• Install O-rings and keycaps: 10 minutes

Wiring diagrams

• Use any of the digital pins except pin 13 (LED)
• Feel free to use pins different than what are in the diagrams

Wiring switch columns: 2 hours, 1 for each split

• Mark on stranded wire where column pins are
• Use wire stripper to cut at each mark and 5mm to the right of the mark, i.e. two horizontal cuts 5mm apart at each mark
• Make a vertical cut between the two horizontal cuts with a knife and remove the insulation to expose the strands
• Split strands into two parts so a column pin can get through
• Solder the wire to the pins

Wiring switch rows and diodes: 4 hours, 2 for each split

• Cut 3~4mm wide stripe off copper sheet with heavy-duty scissors
• Mark positions of row pins on the stripe
• Drill small holes (D~=1mm) at the marks and an extra hole at the end toward the center for wiring the row to the controller
  • Use hammer and nail if no drill at hand
• Diodes with black terminal oriented downward
  • The black terminal is inserted into a hole on the stripe and bent upward
  • The other terminal is wrapped around a row pin for at least one complete circle
• Make sure the stripe doesn’t touch any exposed part of column wires
• Solder diodes to row pins
• Solder diodes to copper stripe. When solder is applied with the side (not the tip) of the iron touching the stripe, a small “flooding” area of solder creates a strong solder joint.
• Cut off extra length of diode terminals

Testing and fixing: 20 minutes

• Use a multimeter. Turn the dial to diode sign.
• Red on column, black on row
• Press the key at the column-row. Multimeter should read current.

Connecting the right matrix to controller: 2 hours

• Avoid pin 13 which is for the built-in LED
• Figure out how to route the wires before soldering
• Rows are routed with fairly short wires so either solid or stranded wires work
• Columns are routed with stranded wires for flexibility
• The controller has its program/reset button facing down so it's accessible without opening the case

Connecting the left matrix to USB-C: 1 hour

• Prepare USB-C cable
  • Cut the plugs off
  • Insert the cable into a few O-rings, which can act as stoppers
  • Mark the length to reach the furthest column
  • Make a round cut at the mark with a knife and remove the insulation
  • Remove the silver-colored mesh and paper wrap to expose wires
  • Observe 4 thin wires and 10 thick wires (2 from a twisted pair)
  • Solder 4 thin wires into one
• Pin or tape USB-C cable so it doesn’t move around
• Decide which wire for which column/row
• Color coding helps, e.g. red USB-C wire to red column wire
• Cut wires to proper lengths
• Use soldering iron to remove insulation at the end of each wire
• Wrap strands around a soldering joint and solder

Connecting left and right rows: 30 minutes

• Prepare USB-C cable to expose wires at the other end
• Pin or tape USB-C cable so it doesn’t move around
• Cut wires to proper lengths
• Use soldering iron to remove insulation at the end of each wire
• Wire rows of the left half to rows of the right half, so logically there are 5 rows.

Connecting left columns to controller: 30 minutes

• Ground the silver-colored mesh to GND pin of the controller. Ghost keys can pop up without this.
• Wire columns of the left half to the controller

Uploading firmware

• Note down which controller pin each row/column is wired to. There are 5 rows and 12 columns. Column 0 is where left shift is and column 11 is where right shift is.
• Plug in USB mini cable to the controller and connect the keyboard to a computer.
• Download Teensyduino which extends Arduino to support Teensy controllers.
• Clone firmware repo on the computer.
• Update keyboards/darknight/darknight.ino with above-noted row pins and column pins.
• Create a symbolic link in Arduino's libraries directory to the cloned firmware directory.
• Open darknight.ino in Arduino IDE.
• In the IDE, change "Tools > Board" setting to be "Teensy LC" or "Teensy 3.2/3.1" depending on the controller chip, and change "Tools > USB Type" setting to "Keyboard + Mouse + Joystick".
• Use "Sketch > Verify/Compile" to make sure the firmware compiles fine, then use "Sketch > Upload" to upload the firmare to the controller.
• Test the new keyboard!

It happened once that pressing any two keys among Q, W, E, R and T at the same time would also produce Tab. It was fixed by swapping the wires connecting to the first row and the second row. The exact cause is still unknown but a guess is along the line of induced current.

Closing the cases: 10 minutes

• Make sure USB mini cable and USB C cable fit in the cable hole
  • May need to enlarge the cable hole with a filer
• Insert screws and fasten the cases with nuts

Installing tenting racks: 5 minutes

• Cut 8mm pieces from USB-C insulation and insert rack feet into the pieces to increase friction on surface
• Slide each case into a rack and adjust tenting angle

Updates

New build on 7/7/2019

Change of color scheme. Maybe call it WhiteKnight.

New build on 12/30/2020

What else is better than building another keyboard in these holidays! I call this one RedBaron.

Now I have three such keyboards, Darknight trapped at work due to the pandemic, WhiteKnight for working at home and RedBaron for personal use.

For this build, I just used stranded wires for the matrix. It turns out to be simpler since the wires can be routed to the controller directly.

High-angle tenting on 11/12/2021

A bridge connecting the two halves turns out to be a good solution for high-angle tenting. The bridge is simply the two tenting racks joined together, with small adjustments in size.

With a little more engineering, the entire structure can be locked by tension so it can be easily moved around.