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.
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-D4 | GDEH0154D67 | BMA423 | DS3231 | Battery | ADC | UART | Buttons |
|---|---|---|---|---|---|---|---|
| GPIO 1 | TX | ||||||
| GPIO 3 | RX | ||||||
| GPIO 4 | Button 4 | ||||||
| GPIO 5 | CS | ||||||
| GPIO 9 | RES | ||||||
| GPIO 10 | DC | ||||||
| GPIO 12 | INT2 | ||||||
| GPIO 13 | |||||||
| GPIO 14 | INT1 | ||||||
| GPIO 18 | SCLK | ||||||
| GPIO 19 | BUSY | ||||||
| GPIO 21 | SDA | SDA | |||||
| GPIO 22 | SCL | SCL | |||||
| GPIO 23 | MOSI | ||||||
| GPIO 25 | Button 2 | ||||||
| GPIO 26 | Button 1 | ||||||
| GPIO 27 | INT | ||||||
| GPIO 32 | Button 3 | ||||||
| GPIO 33 | ADC |
Main Component Datasheets
- Microcontroller ESP32-PICO-D4
- USB-Serial CP2104
- E-Paper Display GDEH0154D67
- Display Connector AFC07-S24ECC-00
- 3-Axis Accelerometer BMA423
- Real Time Clock DS3231
- Battery LiPo Battery 3.7V 200mAh 402030
- LDO Voltage Regulator ME6211C33M5G-N
- Battery Connector BOOMELE 1.25T-2PWT
- Micro USB Connector U-F-M5DD-Y-L
- Tactile Buttons K2-1114SA-A4SW-06
- Vibration Motor 1020
- PCB Antenna SWRA117D
Open Source Hardware & Software
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?
- 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?
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.
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Read my other articles on embedded systems design.
Happy learning to you!