Adafruit 2.9 Grayscale eInk / ePaper Display FeatherWing - 4 Level Grayscale

Easy e-paper comes to your Feather with this breakout that's designed to make it a breeze to add a monochrome eInk display. Chances are you've seen one of those new-fangled 'e-readers' like the Kindle or Nook. They have gigantic electronic paper 'static' displays - that means the image stays on the display even when power is completely disconnected. The image is also high contrast and very daylight readable. It really does look just like printed paper!

Adafruit have liked these displays for a long time, so wouldn't a custom e-paper FeatherWing with buttons make a ton of sense? This 'Wing is tested to work with all of Adafruit's Feathers, from the ESP8266 to the M0. It has built in memory buffering so it can work with chips as small as the '32u4 and '328. It does use a lot of pins: the 3 SPI pins, and up to 4 control pins to manage the SD card slot and SRAM. Plus 3 optional buttons are available for Feathers with available pins.

The FeatherWing sports a 2.9" grayscale display with 296x128 pixels. Each pixel can be white, light gray, dark gray or black. Compared to 'tri-color' displays with a red pigment, this display takes a lot less time to update, only about a second instead of 15 seconds!

Using Adafruit's CircuitPython or Arduino libraries, you can create a 'frame buffer' with what pixels you want to have activated and then write that out to the display. Most simple breakouts leave it at that. But if you do the math, 296 x 128 pixels x 2-bits-per-pixel = 9.5 KBytes. Which won't fit into many microcontroller memories. Heck, even if you do have 32KB of RAM, why waste 9KB?

So Adafruit did you a favor and tossed a small SRAM chip on the back. This chip shares the SPI port the eInk display uses, so you only need one extra pin. And, no more frame-buffering! You can use the SRAM to set up whatever you want to display, then shuffle data from SRAM to eInk when you're ready. The library Adafruit wrote does all the work for you, you can just interface with it as if it were an Adafruit_GFX compatible display.

Adafruit even tossed on a MicroSD socket so you can store images, text files, whatever you like to display. Comes assembled and tested with socket headers that you can plug your Feather right into, no soldering required!

Check out Adafruit's page for Arduino and CircuitPython example code and libraries.