LightInk project

E-Ink ESP32 powered Watch that can run solely on solar power!

What is it?

The main porpose of LightInk project is to have a functional and basic E-Ink watch that can be powered via Solar cell entirely. The power consumption is around 2uA just updating time, therefore a 200mAh battery like "Watchy" has can last around 400 days! (or powered by a small solar cell)

The project is based around the "Watchy" idea, but requires specific HW to reach these low power levels. Basically differs in:

• Has a better TPS63900 power source of 2.6/2.9V
  • More efficient (DC-DC 75nA quiscent, 1A, 1.8-5V regulation, which 2 configurable voltages)
  • This is enough to power ESP32/RTC/Eink and WiFi under all conditions
• Does not have accelerometer (too much power!, even disabled, uses 1uA)
• Does not have solar cell regulation, is connected directly to batery
• Piezo speaker support
• LED light to see display in dark
• Capacitive touch instead of buttons
• Support for LORA/GPS, but yes, they use too much power! (only turn on to send a signal)

More info

Hackaday.io project page: https://hackaday.io/project/205564-lightink

Youtube channel: https://www.youtube.com/channel/UC85IYb1iQYl5axvtkAJRysg

Videos: ![Demo solar video] ![Demo features video]

Other links: https://www.hackster.io/news/the-lightink-watch-pairs-a-solar-panel-with-epaper-to-deliver-theoretically-infinite-battery-life-ac8c0fdec287

What is done already ?

The project goals are:

• Ultra low consumption <0.5 mAh/day!
  • Custom Display Driver, reduce booster times/ LUT, etc..
  • Implement a uSPI and display update from wake sleep stub (<1ms! ESP32 on time)
• Basic UI functionality and Widgets
• Features
  • LED light
  • Vibration
  • Speaker
  • GPS
  • Lora receive, BPSK send signals
• Time accurate
  • Manual calibrate drift and adjust it
  • 1ppm Target (now 10ppm)
  • NTP sync - Wifi - AutoZone
• Battery Power support
  • Track battery & estimate in ULP
  • Auto power save
  • Night time, saving ours
• Touch Settings
  • Capacitive Touch functionality
  • Touch configuration - Sensitivity
• Watchface configuration
  • Refactor watchface to be modular with uSPI update
  • Moon Indicator
  • SunSet Sunrise
  • Tides
  • Pictures, etc
• Configurable Alarms
• BT - Companion App
• Support other boards
  • Watchy v1.0 -> Watchy 1.0 Branch

The purpose of this project

Have fun optimizing the hell out of this ESP32 to make it low power enough for a solar cell. This all started as a challenge, that luckily it is starting to look like a real thing after many years.

My plan is to continue developing and adding features/fixes for my personal unit use. I doubt it will become a comercial product since building a unit requires a lot of soldering. However I am happy if someone can change my mind on how to mass produce it easily. :)

Repo structure

lightink/
├── firmware/
│   ├── main/         # The LightInk firmware code
│   ├── components/   # Other components & subprojects used in the builds
│   └── esp-idf/      # The ESP-IDF version used to build (it has changes compared to upstream)
│   ...               # Other misc files like partitions / sdkconfig / ...
│
├── hardware/
│   ├── pcb/          # Schematics, BOM and diagrams
│   └── case/         # STL files for from and back
│
├── docs/
│   ├── images/       # images of the project
│   ...               # Hisotory and important docs
│
├── README.md
└── LICENSE

More info

• 📖 History
• 🛠️ Hardware
• ✨ Hardware - Case
• ⚡ Hardware - PCB

How to build the firmware?

It should be quite straightforward: Just clone every submodule, use setup.sh and then idf.py to build:

git submodule update --init --recursive
cd firmware && ./setup.sh && idf.py build flash monitor

Helping the project

Just push to a non protected branch and ask for PR. Any contribution is welcomed.

If you want to build a unit for yourself, or support existing ESP32 HW (like watchy), please feel free to add support.