Watchy: An Open Source E-Paper Display Watch

Watchy is an ESP32 based smartwatch that uses e-paper display, fully open-source, both hardware as well as software.

Watchy is designed and manufactured by Squarofumi (SQFMI) the same company that also built the Badgy (Badgy is a rechargeable IoT badge with an e-ink display and WiFi connectivity).

It has a minimalistic design using the PCB as the watch body, although users can customize it with different 3D printed enclosures and watch straps.

It is a smartwatch that is also a wearable development platform, allowing users to create their own experience.

Watchy: An Open Source E-Paper Display Watch 1
Watchy: An Open Source E-Paper Display Watch 2

What features it has?

  • Ultra-low-power e-paper 1.54″ display with 200 x 200 resolution and wide viewing angle
  • Very popular ESP32-PICO-D4 SoC based design
  • Wi-Fi & Bluetooth LE connectivity
  • 3-axis accelerometer with gesture detection
  • Real-time clock for accurate time keeping with calendar and alarm functions
  • Built-in USB-to-serial adapter for easy programming
  • Vibration motor for alerts
  • Four tactile buttons for configuration and user interface
  • Small in Size, only 34mm x 46mm, height is only 9.5mm and weighs 13 grams
  • Open source hardware & software
  • Tons of examples & cool watch faces
  • 3D case designs (stls) to customize your watchy (and watch straps), injection-molded plastic case

ESP32 Pinout

ESP32-PICO-D4GDEH0154D67BMA423DS3231Battery ADCUARTButtons
GPIO 4Button 4
GPIO 25Button 2
GPIO 26Button 1
GPIO 32Button 3

Main Component Datasheets

Open Source Hardware & Software

Watchy: An Open Source E-Paper Display Watch 3

Watchy is fully open source under the MIT License and OSHWA-certified.

How much is Battery Life?

As per their documentation:

Watchy wakes up every 60 seconds to check the accelerometer, real-time clock and updates the E-Paper display with the latest information. Certain watch faces also turn on WiFi to fetch weather data.

With only timekeeping, Watchy should have a battery life of 5-7 days, while with fetching data over WiFi, it should last between 2-3 days. These numbers can be extended through further optimizations (e.g. sleep during off-hours, waking up only on motion/tilt, etc.).

What could be done better?

Watchy: An Open Source E-Paper Display Watch 4
  • As seen in the schematic, it uses LDO to generate 3.3V to power ESP32 and other parts of the circuit, in order to reduce the power consumption, a high-efficiency, low quiescent curremt DC-DC Converter could be used. The LDO used has supply current requirement of 40uA.
  • The battery sensing circuit uses two 100K resistors as a voltage divider, this will always drain ~5uA current per volt, so for battery voltage say 3V, it will consume 15uA continuously. We can use a MOSFET to connect, disconnect battery voltage to the divider circuit. With this, we can use a divider circuit only when battery voltage sensing is required.
  • Some leakage in USB-UART section will also be there due to its connection to ESP32.

Read more information on low power embedded systems design considerations.

What is the cost, where to buy from?

Watchy: An Open Source E-Paper Display Watch 5

One can buy Watchy from crowd supply, it had a successful campaign.

  • Watchy Kit + Case is available for 59$ which includes an E-Ink display, Watchy assembled printed circuit board, battery, double-sided tape, wrist strap, and injection-molded plastic enclosure, all safely nestled in an attractive and instructional box.
  • Anodized Aluminium Case is available for 49$: A CNC aluminum case for Watchy, including an anodized top piece, an anodized bottom piece, four anodized buttons, and four stainless steel M3 screws. In total, it will add 25 grams of pure ruggedness to your Watchy Kit (not included).

Watchy is a very good wearable development platform for developers and I can’t wait to see interesting use cases it can be used in.

If you are interested in an E-paper display, this might be useful for you.

I hope you found this post interesting.

If you like the post, please share it with others. Any suggestions or comments, let me know here.

Read my other articles on embedded systems design.

Happy learning to you!

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.