Easy e-paper finally comes to microcontrollers with these breakouts and shields that are designed to make it a breeze to add a tri-color 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 has liked these displays for a long time, but they were never designed for makers to use. Finally, we decided to make our own!
Using an Adafruit Arduino library, 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, 264 x 176 pixels x 2 colors = 11.5 KBytes. Which won't fit into many microcontroller memories. Heck, even if you do have 32KB of RAM or more, why waste 12KB?
So we 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 has does all the work for you, you can just interface with it as if it were an Adafruit_GFX compatible display.
For ultra-low power usages, the onboard 3.3V regulator has the Enable pin brought out so you can shut down the power to the SRAM, MicroSD and display.
There is even an added MicroSD socket on the breakouts and FeatherWings, so you can store images, text files, whatever you like to display. Everything is 3 or 5V logic safe, so you can use it with any and all common Maker microcontrollers.