The crkbd hotswap trackpoint module is built from a PS/2 trackpoint taken from a replacement thinkpad keyboard. The trackpoint is disassembled into the sensor module and controller board to reduce the footprint, connected to a driver board plugged into the OLED socket, and mounted under a modified OLED cover held in place with an additional standoff secured to the pro-micro.
The trackpoint and OLED modules can be swapped by changing the OLED cover, standoffs, and socketed module, and reflashing.
For firmware see https://github.com/manna-harbour/qmk_firmware/blob/crkbd/keyboards/crkbd/keymaps/manna-harbour/readme.org.
- Use trackpoint model R61 so that the controller board can be separated from the sensor module in order to fit entirely below the mounting plate.
- This trackpoint module can be found in thinkpad keyboard model number MW-89US, but only some parts numbers (including 39T7148 and 42T3241) and not others (including 39T0928), so check the parts number with the seller before purchase.
- Remove only the 2 outer screws retaining the back cover. Do not remove the 4 screws that have cutouts in the cover.
- Remove trackpoint cap.
- Remove the G and H keycaps.
- Remove the 2 screws under the keycaps securing the module to the keyboard.
- Remove the module from the keyboard.
- Bend the flex cable back and forth a few times until it breaks.
- Remove the 2 screws holding the sensor module to the controller board.
- Desolder the connection between the sensor module and the controller board, taking care to avoid lifting pads.
- Rejoin the sensor module and controller board with 4-wire ribbon cable.
- Solder 5-wire ribbon cable to controller board pads for connection to driver board.
- Add male-female standoffs to OLED cover standoffs so as to match keycap height.
- Alternatively, replace standoff pairs with single female-female standoffs for greater rigidity.
- An extra male-female standoff is required at the top end of the mounting plate to prevent movement.
- After mounting the mounting plate on all 3 standoffs, glue a 1mm nut to the pro-micro to secure the extra standoff while still permitting re-installation of an OLED module.
- The trackpoint sensor is a strain guage and needs to be mounted rigidly.
- Reproduce the standard OLED cover outline in 3mm acrylic or stronger material to avoid flex.
- Stack the standard OLED cover on the mounting plate and mark through the standoff holes.
- Place mounting plate on standoffs, position sensor module on top aligned with home row and without overlap, and mark through mounting holes.
- Mark the sensor cutout hole half way between the sensor module mounting holes.
- Mark center of extra standoff hole centered horizontally and located 3mm from top edge.
- Drill mounting holes, standoff holes, and sensor cutout pilot hole with 2mm bit.
- Drill from the top side to avoid chipping.
- Redrill sensor cutout hole with 8mm bit.
- Use 5 column strips by 6 rows of stripboard.
- The stripboard is populated, component side up, as shown in the following table. The top row is the trackpoint controller board pad function (and connecting wire colour used in the photos). The next 4 rows give connections for each component. The bottom row is the pin header.
| RST (green) | GND (orange) | VCC (red) | CLK (yellow) | DATA (blue) |
| 2u2 - | 2u2 + | |||
| 100k | 100k | |||
| 4k7 1/2 | 4k7 1/2 | |||
| 4k7 2/2 | 4k7 2/2 | |||
| GND | VCC | SCK | SDA |
- If using an SMD capacitor, first solder cut resistor legs, place component pad-side-up, bend legs to hold component, cut legs level with top of component, and drag solder between legs and pads.
- If using a regular capacitor, shift all other components up one row, connect the capacitor to the bottom row below the pin header, and position the capacitor body below the bottom edge.
- If using a low profile socket, first solder all components except for the pin header, then mount in socket, level the stripboard, and solder the pin header, as there needs to be a gap between the pin header and stripboard to accommodate the height of the components.
- Solder ribbon cable from controller board.
- Flash firmware.
- Cover exposed conductive elements with insulation.
- Fold into stack.
- Plug driver board into socket.
- Screw in standoffs.
- Screw sensor module to mounting plate.
- Place new trackpoint cap.
- Screw mounting plate to standoffs.
This documentation is for the crkbd but it should also apply to other split keyboards with similarly positioned OLEDs such as helix, kyria, and lily58. For keyboards with wider OLED covers the trackpoint may fit without separating the controller board from the sensor module, and so the build process will be simplified and other models of trackpoint could be used.
- https://deskthority.net/wiki/TrackPoint_Hardware
- https://github.com/alonswartz/trackpoint
- https://github.com/foostan/crkbd
- https://xkcd.com/243/
