Hey @riotmole, I think I’m probably the resident expert on e-ink and Nerves at the moment, so I’ll do my best to get you pointed in the right direction

Unfortunately, there’s a lot of variation between individual e-ink displays, as the driver chips don’t always support the same features/options. Could you send me some more info about which HAT you have, and I can see what I can do to help?

I have a couple of helper libraries I developed while working on the Goatmire conference badge:

• eink (GitHub)
  • I suggest you start here. You can implement the EInk.Driver behavior in a custom driver module to support your hardware (if your hardware uses a SPI interface, which I guess it does, then you can use the EInk.Driver.SpiDriver helper module - see EInk.Driver.UC8179 for reference)
• dither (hex, GitHub)
  • Used for converting images to B/W with a dithering algorithm. Implements a few basic image processing capabilities
• name_badge (GitHub)
  • This is an example application of how you can use these libraries. It is the software that runs on the Goatmire name badges. You could likely tweak it to work on your rpi zero 2, if you wanted. Note that it is under active development, there’s a few PRs that make some pretty big changes that I’m going to get in this week.

A recommendations:

• Try to find the datasheet for your e-ink display, as well as a reference implementation. This will help you understand which commands are sent to the display.
• E-ink displays often require you to send over a waveform look up table (LUT). They are kinda black magic, they control the electrical charge applied to each pixel to get it to change color. You can mess with them, but normally the manufacturer of the display has a recommended lookup table. If you’re lucky though, the LUT will be programmed into the e-ink driver chip at the factory, and you won’t have to worry about it.