LT7DK PMW3360 Trackball Development Kit

PCB

Front	Back

The PCB has been designed in KiCad EDA 9.0 using the kicad-lkbd libraries.

You can preview the project files using KiCanvas directly in your browser and download the latest fabrication files for JLCPCB from the latest release.

The exported schematic is also available under output/schematics.

PCB Order

Parameters	Value
Base Material	FR4
Layers	2
Dimensions	62 × 84 mm
PCB Thickness	1.6 mm
PCB Color 1	Black
Silkscreen	White
Surface Finish 2	Lead Free HASL or ENIG
Copper Weight	1 oz
Via Covering	Tented
Min Via Hole Size	0.3 mm
Board Outline Tolerance	± 0.2 mm

JLCPCB Specific Options

Mark on PCB

The following JCLPCB specific options are used to serialize PCBs on order. An 8 × 8 mm silkscreen square was added to the PCB to allow for a 2D barcode to be added.

Parameters	Value
Mark on PCB	2D barcode (Serial Number)
- Printing	2D barcode & Number
- Code Type	Data Matrix Code
- Prefix	LKBD_LT7DK_v100
- Unique Number	Remove
- Incrementing Number	YYMM01 (e.g.: 250300)
- 2D Barcode Size	8 × 8 mm
- 2D Barcode Position	Specify Position

Serial numbers are based on the current date using the YYMM01 format for its incrementing numbers. Orders in February 2025 would start then start it at 250300, making the final serial LKBD_LT7DK_v100_250300.

BOM

Part	Ref.	Quantity	Optional	Remarks
PCB	LT7DK PCB	1	❌	See PCB section on how to order it.
Pro Micro Controller	Arduino Pro Micro 5V, Adafruit KB2040 or nice!nano	1	❌	Supports various Pro Micro style controller (including RP2040 based ones) as well as the nice!nano for wireless builds. 3
MCU Socket	DIP-24 Round Socket (Wide, 15.24 mm)	1	✅	Recommended to socket the controller, can be omitted if soldered directly. Compatibles pins are required such as dismantled LED strip male adapters.
Reset Push Button	DIP 2pin Momentary Push Button (6 × 3.5 mm)	1	✅	Used as a reset switch, can be omitted if you flash the controller before installing it or if the controller can be put in bootloader mode from any other means.
Micro Switches	D2FC-F-7N Micro Switch or compatible	4-7	❌	Micro switches for mouse buttons, you do not have to populate all of them depending on how you intend to use the PCB.
PMW3360 Optical Sensor & Lens	PMW3360DM-T2QU + LM19-LSI	1	❌

Firmware

Firmware has been built using the vial fork of QMK.

Wireless Support

To add wireless support to this keyboard, you will need a controller that provides power input and a charging circuit between the top RAW and GND such as the nice!nano.

The PCB itself provides a way to attach a JST-PH connector as well as a slide switch for power management. This slide switch must be set to ON for the charging circuit to work.

This hasn't been extensively tested yet and should be considered experimental (no wireless firmware will be provided for now). The feature was added to the PCB as way for us to prototype a potential wireless keyboard.

References

Inspiration

• aki27kbd trackball_module
• Ploopy Nano Trackball (source)
• Ploopy Adept Trackball (source)
• jfedor2 DIY trackball with scroll ring
• The Orb trackball
• brickbots aball

PCB Designs

• jfedor2 PMW3360 Breakout Board
• jfedor2 PMW3360+RP2040
• asav.dev PMW3360 Module
• SideraKB PMW3360 PCB
• protieusz Omega-Petit

License

This design is licensed under the CERN Open Hardware Licence Version 2 – Strongly Reciprocal (CERN-OHL-S-2.0).

You are free to use, modify, and distribute this design for any purpose, provided that:

• Attribution: Appropriate credit is given, a link to the license is provided, and any modifications are clearly indicated.
• Reciprocity: Any derivative works must be released under the same license.

If you are a retailer or business interested in producing or selling this design or related products, I’d love to discuss it! Please feel free to reach out so we can explore potential arrangements.

Footnotes

1. You can select any PCB color you want but some manufacturers such as JLCPCB may charge you more for uncommon combos (such as Blue PCB + ENIG Surface Finish). ↩

2. The "HASL (with lead)" option is extremely discouraged due to the risk of lead poisoning. We strongly recommend paying the premium for the "Lead Free HASL" option. ↩

3. See Wireless Support for more details. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶