EWatch
EWatch, a programmable ESP32-S3 smartwatch.
EWatch is a programmable ESP32-S3 smartwatch and dev board. Code it by hand like any other Arduino board, or describe what you want and let an LLM write the firmware. You can buy it as a bare board, as a kit to build yourself, or ready to wear. I design and assemble them here in the UK.
Written about EWatch.
- circuit.rocks EWatch: An Open Source ESP32-S3 Smartwatch You Can Program Walks through the hardware, the open firmware and the three versions. Read the article ↗ (opens in a new tab)
- Hackster.io Build and Program Your Own Smartwatch On the five-year build, the power circuit and the open-source drivers. Read the article ↗ (opens in a new tab)
- LinuxGizmos ESP32-S3 powers EWatch smartwatch with open drivers and DIY options Covers the hardware, the three versions and the open-source drivers. Read the article ↗ (opens in a new tab)
Same board in all three.
The PCB
Just the board and the screen: ESP32-S3, USB-C, display connector, assembled and bring-up tested. Bring your own battery, strap and enclosure.
- EWatch mainboard (assembled)
- 1.69" touch display
Pre-order. Ships after certification, estimated April 2027. Cancel any time before it ships for a full refund. Pre-order terms
The Kit
Every part of the watch, laid out for a one-afternoon build. PCB, screen, battery, vibration motor and strap, plus the case CAD files so you can print it, mill it or send it out.
- EWatch mainboard
- 1.69" touch display
- 350 mAh battery
- Vibration motor
- Strap
- Case CAD files (On request)
Pre-order. Ships after certification, estimated April 2027. Cancel any time before it ships for a full refund. Pre-order terms
The Watch
Assembled, tested and pre-flashed. Charge it and start writing watch faces.
- Fully assembled EWatch
- Free USB-C programming cable
- Pre-flashed with latest EWatchOS
Pre-order. Ships after certification, estimated April 2027. Cancel any time before it ships for a full refund. Pre-order terms
EWatch (models EW-PCB-01, EW-KIT-01, EW-ASM-01) will receive security updates until at least 31 December 2029. Security and support
Certification status
What EWatch has to pass before it ships: radio (EN 300 328), EMC (EN 301 489), electrical safety (EN 62368-1), RF exposure, and the UK product security rules for connected devices. The battery has to come with UN38.3 transport test evidence.
As deep as you want to go.
EWatch is a full ESP32-S3 development board, wrist-sized. Write the firmware yourself, the way you would on a Feather or a Watchy. Or paste the open-source drivers and one example project into an LLM and let it write the firmware for you.
Open-source drivers
Drivers for display, touch, IMU, BLE, charging and sleep modes. Call display.text(), imu.steps(), ble.notify(). Everything's on GitHub.
Reference watch faces
Working watch faces you can browse and fork in EWatch Cloud. Read one, change it, flash your version. They also make good context to hand an LLM, because the code already runs.
Vibe-code with an LLM
I run Claude Code inside PlatformIO with the driver headers and one example pasted in as context. Ask for a watch face that shows your next meeting and vibrates 5 minutes before: it usually works first try, because the model has real running code to copy from. When it doesn't, you end up reading the driver yourself.
Standard ESP32-S3 board
Underneath it's a vanilla ESP32-S3 dev board. Program it from Arduino IDE, PlatformIO, or ESP-IDF in C, C++, MicroPython or Rust.
Drop to the metal
Drive peripherals over I²C / UART, write to registers, fold it into your own RTOS task graph. The drivers are open source, so when you outgrow them you can read them.
From hobby to product
Start with the LLM. Drop to the driver layer when you need precision, or to bare-metal when you're counting microamps.
Hardware, documented.
From schematic to wrist.
On the screen
Captures from the watch's 240 × 280 display, shown at their real pixel size.
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Analogue watch face
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The app list
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Quick controls: music, brightness, WiFi and Bluetooth
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Scanning for Bluetooth devices
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Macropad: shortcut keys for your computer
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A pet fly to feed and look after
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A Mario-style platformer
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A Minecraft-style block world
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A Doom-style shooter, played sideways
EWatch Cloud.
EWatch Cloud is a browser-based studio: write firmware, compile it and flash it to the watch, with no toolchain to install. It'll come with an AI assistant grounded in real EWatch code, and a small marketplace so you can share or sell what you make. Still in development, arriving after the first watches ship.
Couldn't save that. Email contact@ewanwills.co.uk instead.
Questions about EWatch.
Is EWatch a smartwatch like an Apple Watch or a Garmin?
No. EWatch is a dev board for people who want to program their own watch. It doesn't track health or fitness out of the box. It's a watch you write the software for.
Which version should I pick?
The PCB if you want an ESP32-S3 board with a good touchscreen for your own project. The Kit if you want to build the watch yourself (you'll need a soldering iron for the battery and the vibration motor). The Watch if you want it assembled, tested and flashed, ready to program.
Do I need to install anything to program it?
No. You can write, compile and flash from Chrome at ewatch.cloud over USB-C. If you'd rather work locally, use the Arduino IDE or PlatformIO. ESP-IDF should work too, but I haven't tested it yet.
Do I need to pay for EWatch Cloud?
The editor, flashing and the project library are free. The AI assistant and other compute-heavy tools run on Cloud credits, which you top up when you need them. Early adopters get a month of the paid features free.
Do I have to use the AI assistant?
No, it's optional. You can write everything yourself in C, C++ or MicroPython, or build it from blocks in Studio.
When will I get it?
Estimated April 2027. Before it ships, the watch has to pass UKCA and CE radio certification. If anything moves that date, I'll post an update straight away.
Is it certified?
Not yet. Radio, EMC and safety testing comes before any sales, and nothing ships until it passes.
Is it waterproof?
No. It hasn't been tested for water resistance, so keep it dry.
Can I make my own case?
Yes. The Kit comes with the case CAD files, so you can print or mill your own.
What strap does it use?
The Watch comes on a 20 mm metal mesh strap with a magnetic latch. Any standard 20 mm strap with spring bars fits.
How long does the battery last?
It ships with a 400 mAh battery. These are calculated battery life figures: I worked them out from the component datasheets, because I haven't measured battery life on production units yet. They assume the screen dims to a screensaver after 5 seconds and sleeps after 20.
Calculated battery life:
- Checking the time and notifications through the day, no WiFi or Bluetooth: about 5 days.
- The same with WiFi syncing every 5 minutes: about 3 to 4 days.
- With Bluetooth connected all day: about 7 hours on the current firmware, which keeps the processor at full speed while Bluetooth is on. Improving that is on my list.
- Screen on the whole time: about 7 hours.
It's a dev board, so your own code decides most of this. I'll post measured figures before the watches ship.
How long does it take to charge?
The calculated charge time is about an hour and a half to two hours from empty over USB-C. I haven't measured it yet.