Kingham Xu's OV-Watch Is a Slick, $20 Open Source STM32 Smartwatch Built Around FreeRTOS and LVGL

With a compact design, 3D-printable case, and a range of features, the OV-Watch is a step above most open source smartwatch projects.

Gareth Halfacree
2 months agoWearables / 3D Printing / HW101

Student and self-described "embedded software and hardware geek" Kingham Xu has built a smart watch around the STMicroelectronics STM32F411 microcontroller, FreeRTOS, and the LVGL graphics library — with a range of slick features, including Bluetooth connectivity, activity tracking and health monitoring, and built-in games.

"This is a smart watch based on STM32 & LVGL & FreeRTOS," Xu explains of the OV-Watch project. "The total cost is about 100 RMB, which equal to about $20 USD. All the hardware and software and 3D print[ed] shell are finished by myself, you can freely modify them if you want. Till now, the version is v2.3.2, and the ROM cost is only about 350kB."

Designed with a slick user interface built in the LVGL graphics library and connected to a colour touchscreen, the OV-Watch offers a range of features above and beyond simply telling the time. There's built-in activity tracking, a calendar, compass, heart rate monitoring, timers and stopwatches, a calculator, and even a selection of games.

"The watch has three modes," Xu writes, in translation, of the OV-Watch. "The first is the normal operating mode, the watch runs normally; the second is the sleep mode, the MCU [Microcontroller Unit] enters the STOP mode, and the [TDK] MPU6050 [inertial measurement unit] is still counting steps; the third is the shutdown mode, the [Texas Instruments] TPS63020 [buck-boost converter] is directly turned off and enabled, and there is no 3V3 power supply at this time, only Vbat has power supply."

The watch has gone through a number of redesigns to reach the major V2.3 release, including the addition of an LED array to boost the accuracy of the photoplethysmogram (PPG) pulse sensor, and a previously available Near Field Communication (NFC) feature was removed. The result is a surprisingly slick device, and one that avoids the bulk of many rival open source smartwatch designs.

More information, in Chinese, is available on the project's GitHub repository, along with hardware design files, case 3D print files, and software source code under the reciprocal GNU General Public License 3; additional details in English are available on Xu's Hackaday.io page.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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