2 layers216.5 × 81.2 mm Delta lambda, the printed circuit board in 3D

Delta lambda

ZMK config for Delta Lambda: A 34-key wireless split keyboard fork of Delta Omega, redesigned for Kailh Choc v1/v2 switches.

Open in PCBKit

Size: 216.5 × 81.2 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 106
Nets: 78
Pads: 476
Tracks, vias: 1,742, 100
Routed: Yes
KiCad: KiCad 10.0 (file 20260206)
Created: 20 Mar 2026
Updated: 28 Aug 2026

Overview

Delta lambda is an open-source printed circuit board by drakeaxelrod, from the drakeaxelrod/delta-lambda repository on GitHub. It is a 2-layer board of 216.5 × 81.2 mm with 106 parts on 78 nets, routed with 1,742 tracks and 100 vias.

Its parts include 34 diodes, 34 switches, 8 resistors, 6 inductors and 4 crystals. It belongs with the keyboards and input boards and the nRF52 and nRF5x boards of this library.

README

README.md

Delta Lambda

ZMK firmware for the Delta Lambda 34-key split keyboard, running on two Seeed XIAO nRF52840 controllers. Based on the delta-omega design.

Layout

Gallium alpha layout with home row mods (GACS order), 34 combos, mouse keys, and 6 layers.

Base (Gallium)

Base Layer

Home row mods (GACS): Gui/Alt/Ctrl/Shift on left, mirrored on right
Hyper (all 4 mods) on W and F
Thumb layer-taps: ESC/Util, Space/Nav, Enter/Num, Bksp/Fun

Nav (hold Space)

Num (hold Enter)

Num Layer

Fun (hold Backspace)

Fun Layer

Util + Mouse (hold Escape)

Util Layer

Game (toggle from Fun layer)

Game Layer

Combos

Type	Timeout	Prior idle	Examples
Vertical (top+home)	80ms	150ms	`@` `#` `$` `%` `^` `+` `*` `&`
Vertical (home+bottom)	80ms	150ms	` `\` `=` `~` `_` `-` `/` `\|`
Horizontal (adjacent)	40ms	280ms	`[` `]` `<` `(` `)` `>` `{` `}`
Multi-key	50ms	200ms	Tab (3-key), CapsWord, Studio unlock
Thumb	—	—	LShift, RShift

Home Row Mods

Setting	Value
Flavor	balanced (positional hold-tap)
Tapping term	280ms
Quick tap	175ms
Require prior idle	150ms
Hold trigger	opposite hand + thumbs only

Thumb layer-taps use balanced flavor with 200ms tapping term for fast layer activation.

Hardware

Component	Detail
Base design	delta-omega
Controllers	2x Seeed XIAO nRF52840
Keys	34 (3x5 + 2 thumb per hand)
Switches	Kailh Choc v1 / v2 (Hotswap)
Matrix	4x10 (col2row)
Connection	USB-C or Bluetooth (5 profiles)

Building

Local (Nix)

bash

nix develop          # enter dev shell
just init            # initialize west workspace (first time)
just build           # build left + right + settings_reset
just bootloader      # download XIAO bootloader
just update          # west update

Outputs go to build/:

delta-lambda-left.uf2 (central)
delta-lambda-right.uf2 (peripheral)
delta-lambda-reset.uf2 (bond/settings reset)

GitHub Actions

Push to config/ or boards/ triggers a build via ZMK's reusable workflow. Download UF2 artifacts from the Actions tab.

Regenerate layer SVGs

bash

just gen-svg    # regenerates assets/svg/layers/*.svg from keymap

Flashing

Double-tap reset on the XIAO to enter UF2 bootloader (mounts as XIAO-SENSE)
Copy the appropriate .uf2 file to the mounted drive
Flash left half first, then right half

To clear Bluetooth bonds, flash delta-lambda-reset.uf2 on both halves, then reflash the regular firmware.

ZMK Studio

Runtime keymap editing is enabled. Unlock with the combo at thumb key positions 30 + 33.

Parts

106

Qty	Value	Footprint	References
34	SOD123	Button_Switch_Keyboard:SOD123	D1, D2, D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23 +18
34	ULP_SW	ScottoKeebs_Hotswap:Hotswap_Choc_V1V2	SW1, SW2, SW10, SW11, SW12, SW13, SW14, SW15, SW16, SW17, SW18, SW19, SW20, SW21, SW22, SW23 +18
8		ceoloide:mounting_hole_npth	MH1, MH2, MH3, MH4, MH5, MH6, MH7, MH8
6	R_1206 _220R	Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder	R1, R2, R3, R4, R5, R6
4		Mousebite_5	X1, X2, X3, X4
2		ceoloide:mounting_hole_plated	H1, H2
2		simple_tht_fp	TH1, TH2
2	C_1206_1NF	Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder	C1, C2
2	LED_0805_B	LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolder	L3, L6
2	LED_0805_G	LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolder	L2, L5
2	LED_0805_R	LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolder	L1, L4
2	R_1206_1MR	Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder	R7, R8
2	SW_RST	ceoloide:reset_switch_smd_side	RST1, RST2
2	XIAO-nRF52840-SMD	Library:smdXIAO-nRF52840	MCU1, MCU2
1	POWER1	power_switch	PWR_SW
1	PWR_SW	power_switch	POWER1

Questions

How big is the Delta lambda PCB?

It measures 216.5 × 81.2 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Delta lambda use?

106 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Delta lambda KiCad files?

From the drakeaxelrod/delta-lambda repository on GitHub, at the commit this page was made from: the board is assets/pcb/delta-lambda.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.

Can I use the Delta lambda design in my own project?

Its repository states no licence, so its author keeps all rights: ask drakeaxelrod before reusing the design.

Category and platform

Keyboards and input nRF52 and nRF5x

Project files

assets/pcb/delta-lambda.kicad_pcbBoard

Show this board on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/boards/drakeaxelrod-delta-lambda" title="Delta lambda in PCBKit" width="100%" height="480" style="border:0;border-radius:12px" allow="fullscreen" loading="lazy"></iframe>

A picture

<img src="https://pcbkit.io/embed/boards/drakeaxelrod-delta-lambda.jpg" alt="Delta lambda" width="1200" height="900">

A picture that opens the board, for a README

[![Delta lambda](https://pcbkit.io/embed/boards/drakeaxelrod-delta-lambda.jpg?size=s)](https://pcbkit.io/boards/drakeaxelrod-delta-lambda)

Source

Repository: drakeaxelrod/delta-lambda
Board file: assets/pcb/delta-lambda.kicad_pcb
Commit: d8f643e
Licence: Not stated
Copies: 2 copies in 2 repositories

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