eInk or ePaper wings allow you to easily connect your Feather to add eInk/ePaper support. There are two different sizes and different color variations for each size. The larger sized eInks include 3 buttons connected directly to GPIOs on the feather.
eInk is a technology that works by attracting or repelling ink droplets towards or away from the screen inside of thousands of capsules. Normally, the white pigments and the colored pigments are opposite charges. When power is removed, the pigments tend to stay in their positions and thus the last thing displayed remains. Over time though, the pigments are bound to move and you get a loss of quality unless the display is periodically refreshed.
For tri-colored and grayscale displays, the different colored pigments are actually different sizes and so they move at different speeds. By timing the attracting and repelling of the pigments correctly, you can draw in different colors. This is why it takes longer to draw with more colors.
The 2.13" monochrome eInk FeatherWing is your basic eInk display. It draws fast and works reliably. The resolution on this display is 250 pixels wide by 122 pixels high. The chip used to drive this display is the SSD1680. This is similar to the type of displays seen in Kindle or Nook.
The 2.13" HD (or High Definition) Tri-Color eInk FeatherWing takes longer to draw, but you can display images or in red, black, or white. The resolution on this display is also 250 pixels wide by 122 pixels high. The chip used to drive this display is also the SSD1680.
The 2.9" GrayScale eInk FeatherWing is a larger display and is able to display in 4 levels of gray. The resolution on this display is 296 pixels wide by 128 pixels high. The chip used to drive this display is the IL0373. There are 3 buttons on the back connected to GPIOs.
The 2.9" Tri-Color eInk FeatherWing is is able to display in red, black, and white. The resolution on this display is also 296 pixels wide by 128 pixels high. The chip used to drive this display is the SSD1675. There are 3 buttons on the back connected to GPIOs.
Just about every small-medium size eInk display made these days has a standard 24-pin connection. The eInk Feather Friend will add all the power supply support circuitry and level shifting so you can attach your favorite display (up to tri-color 4.2") and wire it up to your favorite development board.