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Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →OV-Watch is a DIY smartwatch project by Kingham Xu built around an STM32 microcontroller, FreeRTOS and LVGL. Its creator estimates a build cost of about 100 RMB—roughly US$20—but that is an approximate project figure, not a verified current retail price or a guaranteed cost to reproduce the watch today.
What is the OV-Watch?
OV-Watch is an open-source smartwatch design, not a mass-market product with an established retail price. The project combines embedded firmware with custom watch hardware and a 3D-printed case. Its public files include firmware, board designs and enclosure files, giving technically equipped makers a path to study or reproduce the device.
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The project page describes the architecture as STM32, FreeRTOS and LVGL. A secondary report identifies the specific microcontroller family as STM32F411. The project description’s V2.3.2 snapshot reports roughly 350 kB of ROM use; this is the author’s figure for that snapshot, not an independently measured benchmark. Kingham Xu’s Hackaday project page and Hackster.io’s coverage describe the project and its design.
Is the OV-Watch really only $20?
The roughly $20 claim comes from Xu’s estimate of about 100 RMB, which the project page equates to about US$20. The page does not provide a bill-of-materials calculation method or clarify whether the estimate includes tools, shipping, labor or a particular production quantity. Treat it as the author’s approximate project cost—not a current parts quote, sale price or promise that every builder can complete the watch for that amount.
#1 Best Overall
- Note: you may receive a green OR blue version, which is delivered randomly.
- STM32F303VCT6 microcontroller featuring 256 KB Flash, 48 KB RAM in an LQFP100 package On-board ST-LINK/V2 with selection mode switch to use the kit as a standalone ST-LINK/V2 (with SWD connector for programming and debugging)
- Board power supply: through USB bus or from an external 3 V or 5 V supply voltage External application power supply: 3 V and 5 V L3GD20, ST MEMs motion sensor, 3-axis digital output gyroscope LSM303DLHC, ST MEMs system-in-package featuring a 3D digital linear acceleration sensor and a 3D digital magnetic sensor
- Ten LEDs: LD1 (red) for 3.3 V power on LD2 (red/green) for USB communication Eight user LEDS, LD3/10 (red), LD4/9 (blue), LD5/8 (orange) and LD6/7 (green)
- Two pushbuttons (user and reset) USB USER with Mini-B connector Extension header for all LQFP100 I/Os for quick connection to prototyping board and easy probing
What can the OV-Watch do?
The project description lists basic watch functions, a calculator, timer, calendar, games, NFC card storage and Bluetooth synchronization of time and data with a smartphone. These are documented project features; the available descriptions do not establish independent testing of each feature.
Features vary by hardware revision. The English README’s version table lists a 1.14-inch screen for V1.0 and V1.1, and a 1.69-inch touchscreen beginning with V2.0. It lists NFC for V2.2 but not V2.3, Bluetooth for V2.2 and V2.3, and magnetic charging for V2.2 and V2.3. The Hackaday project page says V2.3 added an LED matrix intended to improve PPG signal strength in the heart-rate section and switched to a double-layer board. That design change does not establish heart-rate accuracy.
What changed after V2.3.2?
The V2.3.2 label and roughly 350 kB ROM figure belong to the Hackaday project-page snapshot. Xu’s English OV-Watch README also documents later changes:
- V2.4.0: Added a bootloader and IAP over-the-air updates over Bluetooth, along with hardware and software fixes.
- V2.4.1: Notes UART I/O deinitialization during sleep, long-press shutdown and a button behavior change. The README says sleep-state current is over 800 μA; it does not give the battery capacity or measurement conditions needed to calculate runtime.
The repository’s documentation can change, so version-specific details should be checked against the README when planning a build.
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Can you build the OV-Watch yourself?
Potentially, if you can handle custom electronics and enclosure work. The project’s files page lists BOM spreadsheets, schematics, Gerbers, firmware and case STL files. Those make the design reproducible in principle, but they do not make assembly effortless: Xu cautions that soldering or replicating the hardware can be difficult.
For the full watch, expect to work through the board files and parts list, arrange board fabrication, assemble and solder the electronics, load firmware, and print and fit the case. The cited project materials do not establish a current parts total or confirm that components are still readily available.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Can you learn LVGL without building the whole watch?
Yes. For readers mainly interested in coding or LVGL interface work, Xu suggests the FriPi STM32F411 development board as a lower-friction learning route when the watch hardware is difficult to solder or reproduce. It is a development board, not the finished OV-Watch or a guaranteed drop-in replacement for its custom hardware. Check that any board you choose has the MCU and peripherals your intended code requires; the project sources do not establish current board availability or a validated cost comparison.
| Path | Best suited to | Hardware effort | Closeness to the watch |
|---|---|---|---|
| Reproduce the full OV-Watch | Makers seeking the wearable and its custom design | Board fabrication, soldering, assembly and case printing | Uses the project’s watch hardware and enclosure files |
| Use an STM32F411 development board | Learning embedded coding or LVGL without first reproducing the watch | Lower than assembling the complete watch, though setup depends on the board | Software-learning route; not the finished watch |
The comparison describes the paths, not their relative prices: no validated current cost comparison is provided.
What is not established?
The project descriptions do not establish battery runtime, independently validated heart-rate accuracy, phone operating-system compatibility, a current bill of materials or present-day retail availability. Bluetooth synchronization and the README’s OTA notes describe project functionality, but do not by themselves establish compatibility with a particular phone or operating-system version. Avoid treating an advertised feature or a sleep-current note as proof of real-world performance.
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