Updated

Updated · raspberrypi.com · Jul 30

Vishal Soni Builds ChronoWatch X2040 With 950mAh Battery and RP2040 Round Display

Updated

Updated · raspberrypi.com · Jul 30

Vishal Soni Builds ChronoWatch X2040 With 950mAh Battery and RP2040 Round Display

Q: Could switching to an alternative ESP32-S3 module instantly solve this minimalist smartwatch's biggest timekeeping flaw?

Yes—switching to a related ESP32-S3 board with an onboard RTC could largely fix the watch’s biggest flaw, but not quite “instantly.” Soni’s core problem is straightforward: his RP2040-based Waveshare round display board lacks a real-time clock, so when the device enters deep sleep it loses time and date. A comparable Waveshare ESP32-S3 round touch module is documented as including a PCF85063 RTC chip, plus battery support, charging, and the same class of IMU sensors. That means the hardware needed to preserve time across sleep is already built in, removing the need to bolt on a separate RTC module. That said, a module swap would still require firmware work. Soni wrote the current watch in the Pico SDK for RP2040, after adapting C libraries and custom touch code. Moving to ESP32-S3 would mean porting the software to Arduino or ESP-IDF, integrating the RTC driver, and retuning power-management behavior. The timekeeping flaw would be easier to solve, but the software would not carry over unchanged. An ESP32-S3 could also improve low-power behavior more broadly, since the platform offers mature sleep modes and is widely used in battery-powered wearables. But RTC retention depends on proper board design and battery backup for the RTC domain, not just the processor family name. So the short answer is that an alternative ESP32-S3 module with an onboard RTC is a strong fix for the problem, but it is a redesign step rather than a drop-in instant cure.

Q: How can a custom smartwatch survive daily use if entering deep sleep erases its memory?

It needs a hardware timekeeper or another always-on source of time; otherwise a watch that loses its clock in deep sleep cannot reliably handle daily use. In Soni’s design, the main weakness is the lack of a real-time clock, or RTC. The RP2040-based watch can sleep to save power, but without an RTC running independently on very low power, the device forgets the current time and date when it enters deep sleep. For a watch, that is a practical deal-breaker unless the user resets or resyncs the time after waking. The most direct fix is to add a small external RTC chip such as a DS3231, PCF8523, or PCF8563. These chips keep time while the main processor is asleep and use little power, often backed by a coin cell or the main battery. On wake, the microcontroller simply reads the RTC and restores the correct time instantly. That would let the smartwatch survive normal daily sleep cycles without losing its core function. A second path is to switch to a board that already includes RTC support. Related round display modules in the same hardware category, including some ESP32-S3-based Waveshare boards, include onboard RTC chips and low-power features that are better suited to wearable timekeeping. Software can help but not solve the core problem. The watch can save settings, dim the screen, use motion-triggered wakeups, and avoid the deepest sleep states, but those are compromises. For dependable everyday use, an RTC is the key upgrade.

1 articles · Updated · raspberrypi.com · Jul 30

ChronoWatch X2040 strips the smartwatch concept back to timekeeping, offering multiple watch faces, 12- and 24-hour formats, brightness control, a stopwatch, screen rotation and a sleep mode.
Soni built it around a Waveshare Round Touch LCD with an integrated RP2040, pairing the module with a 3.7V 950mAh battery, a 3D-printed case and an Apple Watch strap.
Programming became the main challenge: after moving from Arduino to the Pico SDK in C, he modified basic libraries and wrote custom touch functions to detect taps on specific screen areas.
Power management still limits the project because the watch lacks an RTC module, so deep sleep causes it to lose time and date.
Soni is now considering an RTC, alarm and step counter while also trying to make the watch thinner and use a smaller battery.

Sources

raspberrypi.com21d ago

Vishal Soni Develops ChronoWatch X2040, a Simple Time-Focused Smartwatch

Could switching to an alternative ESP32-S3 module instantly solve this minimalist smartwatch's biggest timekeeping flaw?

Why are tech enthusiasts abandoning feature-packed wearables to build custom smartwatches that only tell time?

How can a custom smartwatch survive daily use if entering deep sleep erases its memory?

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1 total

raspberrypi.com21d ago

Vishal Soni Develops ChronoWatch X2040, a Simple Time-Focused Smartwatch

Vishal Soni Builds ChronoWatch X2040 With 950mAh Battery and RP2040 Round Display

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