ZSWATCH: BUILD YOUR OWN OPEN-SOURCE SMARTWATCH
A genuinely open smartwatch on Zephyr RTOS — round touchscreen, full sensor suite, and a dev kit so you don't have to solder a 38 mm board by hand.
ElectronicsWearables
- difficulty
- ●●●●○
- time
- a serious project
- license
- GPL-3.0
- repo
- repo ACTIVE4,000 stars
●●●●○ · a serious project · GPL-3.0 · 4,000 stars · repo ACTIVE
WHAT YOU’LL NEED
- 3D printer + filament — printable parts — files are in the repo
- Electronic parts — full list with part numbers in the repo BOM
- Dev board / microcontroller — runs the project firmware
- Soldering kit + basic tools — one-time buy, serves every future build
Partner
COMPAREE VERDICT
If you want to say you built a smartwatch — a real one, running your own firmware — ZSWatch is the project. Jakob Krantz open-sourced the whole thing on Zephyr RTOS: firmware, KiCad hardware, and a rich sensor suite (round touchscreen, IMU, pressure, magnetometer, mic, flash). We appreciate the honesty in the docs: the bare watch PCB is a tricky ~38 mm SMD board marked 'prototype, not fully tested,' so the sane path is the WatchDK dev kit rather than hand-soldering from zero. This is not a beginner build and not a weekend — it's a serious wearables project — but the payoff is a working, hackable smartwatch that's entirely yours.
IN THE REPO
NOT IN THE REPO
- —Firmware is GPL-3.0; hardware lives in separate KiCad repos
- —CI (KiBot) auto-generates gerbers/BOM/docs
- —The bare Watch-HW is marked 'prototype, not fully tested' — the recommended path is the WatchDK dev kit
- —Chip is the nRF5340 (newer than the old nRF52 versions)
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Partner · KickstarterCORE POWER BANK S: 0.2" thin, 2.8 oz, 5000 mAh with 22.5W fast charging. Semi-solid battery, carbon fiber, IPX7 waterproof.
Videos
Building an Open Source Smartwatch Using Zephyr — Jakob Krantz39:51
The creator's Zephyr Dev Summit 2023 talk — the definitive overview.
Gallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the docs (start here)
- 2.Watch the creator's talk (40 min overview)
- 3.Get the WatchDK dev kit (the recommended path, not hand-soldering)
- 4.Build the firmware (Zephyr RTOS)
- 5.Join the Discord (the community lives here, not on Reddit)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- The bare Watch-HW is a prototype 'not fully tested' — hand-soldering a 38 mm nRF5340 board is expert-level; get the WatchDK dev kit instead
- It's the nRF5340 now, not the old nRF52 — don't follow outdated instructions
- Firmware is GPL-3.0 and hardware is in separate KiCad repos — mind the split if you fork
Can a beginner build this?
Not really. The firmware side is approachable if you know Zephyr, but the hardware is a dense small SMD board. Start with the WatchDK dev kit rather than soldering the bare PCB.
Does it talk to my phone?
Yes — there's an iOS companion app, and Android works via GadgetBridge.
Which chip is it?
The nRF5340 (u-blox NORA-B10), running Zephyr RTOS. Older versions used the nRF52 — make sure your guide matches your board.
What does it cost?
Band $$ — the dev kit is the simplest way in. Current prices are on the site.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
The bare ZSWatch board is a dense 38 mm nRF5340 PCB the project itself marks 'prototype, not fully tested' — hand-soldering it is expert territory. Would you attempt the bare board or take the dev kit route?
Jakob Krantz (jakkra)
Built a fully open smartwatch on Zephyr and grew a real community and dev kit around it. Funded in part by NLnet/NGI0. Honest about which parts are prototype.
Keep building — related projects
Same category, picked by how close they are to this build.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1mo ago
An engineering practice we'd love more projects to copy: the CI pipeline uses KiBot to auto-generate gerbers, BOMs and docs from the KiCad sources on every change, so the fabrication outputs never go stale. Watch the chip generation too — current builds are nRF5340, and older nRF52-era guides will lead you astray. Any Zephyr developers here tempted to make this their daily watch?