Build and Program Your Own Smartwatch

Smartwatches from Apple, Samsung, and others can do a lot, but they aren't designed to let you replace their firmware with something you wrote yourself. Ewan Wills went in a different direction with EWatch, a programmable smartwatch built around an ESP32-S3 microcontroller. It can be treated much like any other ESP32 development board, except this one comes with a color touchscreen, battery, vibration motor, and a case that straps to your wrist.

EWatch has been more than five years in the making, starting with breadboards and hand-wired prototypes before progressing through several generations of custom PCBs. The current board measures just 34 × 28 mm and uses a two-layer ENIG-finished PCB. An ESP32-S3 provides the processing power along with Wi-Fi and Bluetooth Low Energy connectivity, while a 1.69-inch color touchscreen serves as the primary interface.

The watch also contains a 350 mAh battery, vibration motor, IMU, USB-C connection, and a standard 20 mm replaceable strap. I2C and UART interfaces provide additional options for connecting peripherals or experimenting with the hardware.

Much of the development effort went into making the power system behave like something you'd expect from an actual smartwatch rather than a development board with a battery attached. EWatch includes charging circuitry and battery-level monitoring, along with a latching power circuit that lets software completely shut down the watch. But even when shut down, it can still keep track of the time.

On the software side, Wills has tried to make EWatch useful whether you want to write a simple watch face or dig into the hardware. Open source drivers are available for the display, touchscreen, IMU, BLE, charging system, and sleep modes. Developers can use those higher-level interfaces or work directly with peripherals and registers. Firmware can be developed with familiar ESP32 tools including Arduino IDE, PlatformIO, and ESP-IDF, with support listed for C, C++, MicroPython, and Rust.

EWatch is available in three versions using the same underlying hardware. A $78 option includes the assembled PCB and touchscreen, while a $131 kit adds the battery, vibration motor, strap, and enclosure CAD files. A $171 version arrives fully assembled and pre-flashed with EWatchOS.

There are still a few rough edges being worked out, including display connector reliability, enclosure tolerances, and documentation. If these sorts of issues don't concern you too much, you can pick an EWatch up from the project's official website.