E-Paper Display

Disclaimer

This is not an officially supported Google product.

Introduction

This project was an experiment to make a low-power desktop clock, using an e-paper display.

The low-power thing worked out pretty well. Here is the power consumption, on each update, which happens every ~180 seconds:

It later evolved into a full-featured Raspberry Pi epaper display, which pretty much nixed the low power idea, but added a lot of functionality.

Software

This clock was my opportunity to experiment with a few different technologies.

1. The original version used TinyGo is in the microcontroller/tinygo/ subdirectory, running on a Feather M0.
2. The second version, in the microcontroller/arduino/ subdirectory, was written using conventional Arduino technologies, running on a Feather M0 (and later, a Feather M4). This version worked extremely well and was very low power.
3. The third version, in the microcontroller/micropython/ subdirectory, was an experiment with Circuit Python (using a Feather M4), but the memory demands were too high with all the fonts and large graphics.
4. The fourth version, in the microcontroller/rust/ subdirectory, was an incomplete attempt to implement it in Rust on a Feather M0.
5. The fifth version, in the rpi/python/ subdirectory, is implemented on a Raspberry Pi, and has a lot more functionality: TrueType fonts, 4-color greyscale with anti-aliasing, stock charts, etc.

Hardware

I originally chose almost all Adafruit parts for this project, because they are well made, hassle free, and plug together like Legos.

• Adafruit Feather M0 Express
• Adafruit DS3231 RTC Featherwing
• Adafruit Airlift Featherwing
• Adafruit RTL5111 Reset Timer
• Waveshare 4.2" E-Paper Module
• BME280 Temperature/Pressure/Humidity Sensor

The end result was a clock that runs for months on a small LiPo battery.

(Until I switched to a Raspberry Pi, that is...)