I built a picture frame with a greyscale e-paper that runs on battery for years
I worked on a number of digital photo frames, including on ones like that.<p>E-ink is not the most suitable thing for it in its current form.<p>First, large size EPD cost an arm, and a leg, and custom one costs even more.<p>Second, there are no 8 bit EPD controllers as of now a mortal can buy, which means grays look very bad.<p>Third, there are inherent physical limitations which make increasing gray resolution of EPDs quite hard. The precision you want, the slower would the refresh rate be.<p>If somebody is old enough to remember, (saying this as a 30 years old is indeed amusing to myself) the last active matrix monochrome LCDs had 8 bit, and more of gray resolution, but they are all discontinued now, or cost an arm, and a leg as "medical imaging" specialty.