2 layers65 × 30 mm
Rgb to hdmi
hoglet67/RGBtoHDMI
Bare-metal Raspberry Pi project that provides pixel-perfect sampling of Retro Computer RGB/YUV video and conversion to HDMI
36 parts1kGPL-3.0
2 layers129.8 × 99 mm
Ambra
stozi/ambra18Kalmar/A. Dux-based 34-key split ortho keyboard
- Size
- 129.8 × 99 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 36
- Nets
- 26
- Pads
- 538
- Tracks, vias
- 709, 91
- Pours
- 277
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 19 Feb 2025
- Updated
- 28 May 2026
Overview
Ambra is an open-source printed circuit board by stozi, from the stozi/ambra repository on GitHub, published under the GPL-3.0 licence. It is a 2-layer board of 129.8 × 99 mm with 36 parts on 26 nets, routed with 709 tracks and 91 vias.
Its parts include 1 IC and 1 switch. It belongs with the AVR (ATmega, ATtiny) boards of this library.
README
README.mdAmbra
A Kalmar/A. Dux-based 34-key split ortho keyboard. ZMK shield
Included from Kalmar
- power switch
- reset button
- solder jumpers to mount the MCU the same way on both sides
Changes from Kalmar
- thumb keys mount at 90° with pogo pins and 3D-printed magnet brackets
- besides Kailh Choc, support for Gateron KS-33, both hotswap only
- ground plane for some ESD protection, new pinout
- JST PH battery connector
- perforations to remove the tab for wired builds
- For wired builds: switched from TRRS jacks to RTLECS magnetic pogo pin connectors (also used to mount the thumb keys) to improve damage resitance
If you don't need fold-down packability or can't get the magnets, you can run a 9mm or longer M2 bolt through both brackets. However, any fall will then be more likely to cause damage.
Consider putting a non-conductive coating between the JST connector's mount points and the battery. Remove remnants of perforations on the thumb-key board before attaching the bracket. Personally, I solder the top-side jumpers to mount the MCUs component-side up so I can see the LEDs, and keep them safe under a case handcrafted from plumbing silicone.
Passed basic testing.
BOM
| Item | Qty | Notes |
|---|---|---|
| SuperMini NRF52840 MCU | 2 | inc. sockets. Alternatively, ProMicro/Elite-C for a wired build |
| Kailh Choc V1 | 34 | key switches. Alternatively, Gateron KS-33 |
| Choc hotswap sockets | 34 | Alternatively, Gateron KS-33 hotswap sockets |
| Keycaps | 34 | 1U. If using KS-33 switches, STL files are provided to print your own 'MX stem, Choc-1U-spaced' caps |
| Magnets | 2 | D6×3mm annular cylinder |
| RTLECS MG03254 3-pin | 2 straight m, 2 90° f | magnetic pogo-pin connectors |
| MSK-12CO2 | 2 | power switch |
| SMD button 3×4×2 | 2 | reset switch |
| 301230 li-po | 2 | battery |
| JST PH right-angle 2-pin | 2 | battery connector |
| JST wire | 2 | solder & shrink tube to battery wires, no crimping needed, or battery already with connector |
| M3 machine screws, 3mm | 2 | flathead, couples with magnet |
| M3 thin hex nuts | 2 | |
| M2.5 tapered head machine screws, 7mm | 2 | holds magnet |
| M2.5 thin hex nuts | 2 | |
| M2 flat head machine screws, 8mm | 6 | for brackets |
| M2 thin hex nuts | 6 | |
| OPTIONAL: RTLECS MG03254 cable and extra RTLECS 90° female connectors as listed above | 2 of each | For a wired build: cut, solder and shrink-tube the two wires together |
Parts
36| Qty | Value | Footprint | References |
|---|---|---|---|
| 17 | SW_PUSH | my syms-foots:Choc-and-KS33-Hotswap-Choc-1U | SWr1c1, SWr1c2, SWr1c3, SWr1c4, SWr1c5, SWr2c1, SWr2c2, SWr2c3, SWr2c4, SWr2c5, SWr3c1, SWr3c2, SWr3c3, SWr3c4, SWr3c5, SWr4c1 +1 |
| 6 | , , , , , | ||
| 4 | Breakaway Tabs | kbd_local:Breakaway_Tabs | BT3, BT3, BT3, BT3 |
| 1 | Hole | enki_lib:HOLE | H1 |
| 1 | ProMicro_r | my syms-foots:ProMicro_duplex_clean | U1 |
| 1 | SW_PUSH | my syms-foots:reset-SW_3x4x2_2legs_x2 | RSW1 |
| 1 | SW_SPDT | my syms-foots:switch_MSK-12C02_smd_x2_topor | SW1 |
The 31 most common of 36 parts.
Questions
How big is the Ambra PCB?
It measures 129.8 × 99 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Ambra use?
36 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 Ambra KiCad files?
From the stozi/ambra repository on GitHub, at the commit this page was made from: the board is ambra.kicad_pcb and its schematic ambra.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Ambra design in my own project?
Its repository publishes it under the GPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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