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An open-source, solar-powered E-Ink smartwatch. By re-implementing SPI in the ESP32's RTC wake stub and using a low-quiescent buck-boost converter, it reduces active boot time to under 1ms, delivering up to 10 months of battery life on a 100mAh charge.
LightInk is a great example of what happens when a constraint is pushed to the extreme.
The project pushes the chip into an ultra-low-power regime: wake stub execution, custom SPI in RTC memory, sub-millisecond display updates, then straight back to deep sleep. That is just a genius engineering move you only find when the constraint is taken seriously enough.
And that is what makes the product logic interesting. Once you design around E-Ink, solar power, power-gated features, and obsessive energy budgeting, the watch becomes a very different kind of wearable: a 90s solar digital watch rebuilt with ESP32, E-Ink, LoRa, GPS, touch, and open-source hardware.
Not a polished consumer device yet, but a very fun reminder that extreme constraints can produce much more interesting product directions.
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About LightInk on Product Hunt
“E-Ink watch that can run solely on solar power”
LightInk was submitted on Product Hunt and earned 9 upvotes and 1 comments, placing #23 on the daily leaderboard. An open-source, solar-powered E-Ink smartwatch. By re-implementing SPI in the ESP32's RTC wake stub and using a low-quiescent buck-boost converter, it reduces active boot time to under 1ms, delivering up to 10 months of battery life on a 100mAh charge.
LightInk was featured in Open Source (68.4k followers), Hardware (11.4k followers), Wearables (182.3k followers) and GitHub (41.2k followers) on Product Hunt. Together, these topics include over 39.3k products, making this a competitive space to launch in.
Who hunted LightInk?
LightInk was hunted by Zac Zuo. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
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Zac Zuo
Hi everyone!
LightInk is a great example of what happens when a constraint is pushed to the extreme.
The project pushes the chip into an ultra-low-power regime: wake stub execution, custom SPI in RTC memory, sub-millisecond display updates, then straight back to deep sleep. That is just a genius engineering move you only find when the constraint is taken seriously enough.
And that is what makes the product logic interesting. Once you design around E-Ink, solar power, power-gated features, and obsessive energy budgeting, the watch becomes a very different kind of wearable: a 90s solar digital watch rebuilt with ESP32, E-Ink, LoRa, GPS, touch, and open-source hardware.
Not a polished consumer device yet, but a very fun reminder that extreme constraints can produce much more interesting product directions.