ChronoWatch X2040 Is a DIY RP2040 Round-Screen Watch

Not every wearable needs a heart rate sensor, a companion app, and a subscription. Vishal Soni built the ChronoWatch X2040 around a deliberately narrow premise: it tells the time, it runs a stopwatch, and it does nothing else. The hardware is an off-the-shelf Waveshare RP2040-Touch-LCD-1.28 board — about $23 to $29 — dropped into a 3D-printed case with a LiPo battery and a handful of screws.

• Built on the Waveshare RP2040-Touch-LCD-1.28, a $23 to $29 board with a 1.28-inch round touchscreen
• Powered by a 3.7V 950mAh LiPo battery measuring 35 x 25 x 10 mm
• Custom 3D-printed case designed in Tinkercad, assembled with M2 heat inserts
• Firmware written against the Pico C/C++ SDK; project files at github.com/vishalsoniindia/ChronoWatch-X2040

Why the RP2040 Is a Good Fit for a Wearable

The RP2040 is not the obvious choice here. It has no wireless radio, no low-power sleep states as aggressive as a purpose-built wearable MCU, and no hardware floating point. What it does have is a very well documented C/C++ SDK, programmable IO blocks that make driving an unusual display straightforward, and a level of community support that means almost any problem you hit has already been solved in public.

For a project whose scope is a clock and a stopwatch, those tradeoffs land in the right place. The compute demand is trivial. What actually matters is display driver quality, touch responsiveness, and how cleanly you can implement a sleep timer — all areas where the Pico SDK gives you direct control rather than an abstraction layer to fight.

The 950mAh battery is generous for the load. A 1.28-inch panel with adjustable brightness and a sleep timer is the dominant draw by a wide margin, which means runtime is governed almost entirely by how often the screen is lit rather than by anything the microcontroller does.

What Does the Watch Actually Do?

The feature list is short and intentionally so: time and date with 12-hour and 24-hour formats, a stopwatch, adjustable brightness, screen rotation, a sleep timer, multiple watch faces, and touch controls. There is no phone pairing, no notification mirroring, and no network connectivity of any kind.

That constraint is the design, not a limitation the builder ran out of time to fix. A watch with no radio has no pairing to lose, no app to update, and no account to manage. It also sidesteps the entire power budget problem that makes connected wearables a charging chore. Whether that appeals to you is personal, but as an engineering exercise the scoping is disciplined and the result is coherent.

Build Cost and What Is Actually Open

Worth being precise about the licensing, because it is a mixed model. The 3D case files are freely available, so you can print and iterate on the enclosure at no cost. The firmware source is offered through the project repository for $4.99. That is a modest ask for a solo maker supporting their own work, and the hardware itself is entirely off the shelf, so nothing about the build locks you in — you could write your own firmware against the same board with the Pico SDK if you preferred.

Total parts cost lands somewhere around $30 to $40 once you add the battery, connector, and hardware to the display board. For a first wearable project that is a low-risk entry point, and the fact that the display board arrives fully assembled removes the hardest part of any watch build.

Where It Sits Among Recent Small-Screen Builds

This is the third compact display project worth a look in recent weeks across our mini computers coverage, and each one picks its panel technology to match its data. The ZecTrix Note 4 uses e-paper because notes change slowly. The Token Monitor uses a bright LCD because usage counters update constantly. The ChronoWatch uses a round touchscreen because a watch face wants to be round and a watch wants to be poked.

That is the quiet lesson running through all three. The microcontroller is rarely the interesting decision anymore. The display and the power budget are where a small-form-factor project succeeds or fails, and picking those to fit the actual data is most of the design work.

Worth a Weekend

If you have wanted to build something wearable but bounced off the complexity of a connected device, this is about as approachable as the category gets. Off-the-shelf display board, printable case, a well-trodden SDK, and a scope small enough to finish. That last one matters more than most makers admit.

Sources: CNX Software — August 3, 2026; ChronoWatch X2040 on GitHub — August 2026.