Building an E-Ink Calendar, and a UI Toolkit along the way #eInk @tikurahul

Rahul Ravikumar posts:

Building a E-Ink based dashboard which would keep track of my meetings among other things. Given the always-on nature of the E-Ink display, this would help me better manage by schedule during a typical work-day especially given I tend to miss Google Calendar notifications a lot.

I took an off-the-shelf approach for the hardware. I purchased an InkPlate 6 which was originally crowd-funded on CrowdSupply.

The E-Ink display is from a recycled Kindle e-reader, which means its a pretty great display. It has 2 modes including a 2-bit per pixel gray-scale mode and monochrome. It supports partial updates in monochrome mode. The display is connected to a ESP 32, with built-in WiFi. All we need to do is to hookup the display to a PC via a USB cable and power it on. The display also comes with a nice 3D printed enclosure.

The InkPlate 6 supports MicroPython, and recently the libraries powering the display were opensourced. This gave me a decent foundation to build on top-of.

The first step to showing events from Google Calendar is to be able to complete an OAuth2 flow. I decided to use the device flow given the limited input capabilities of the ESP 32.

MicroPython does not have any libraries that work with OAuth2, so I decided to write one. Here is the PR that I eventually made to the micropython-lib GitHub repo which adds support for this specification. This ended up being pretty straightforward, given my familiarity with OAuth2 (having authored this library before).

The InkPlate has a decent Graphics API, but rather than having to hard-code coordinates to render UI i decided to take minor detour and build a mini UI Toolkit from first principles based on the graphics primitives that were supported. I took a lot of inspiration from the existing Android UI View system and build a small subset of those APIs.

Read more here.