In case you're wondering and don't want to click around, the display is a standard Adafruit 5.83'' eInk panel: https://www.adafruit.com/product/6397
> Image update time - 25 ºC - - 4 - sec
I'm guessing you could probably push that somewhat by going beyond the specifications, would wager a guess how far though.
The thing is, Eink's waveform is kind of secret afaik, everyone has different tuning.
We had some secret eink sauce (propriety waveforms) to get the high refresh rates and colour contrast without a full flashing screen reset, but even then you need to run longer maintenance refreshes occasionally.
Pixels are just vertical columns of viscous fluid with charged ink particles. A waveform is just voltage changes over time to these columns to shift the particles up and down. More black to the top = darker shade of grey. Colour (in the gallery display, at least) is the same, just with each CMY particle group having different charges and responses to different waveforms.
Every once in awhile this vertical column gets messy with loose particles distributed through it (ghosting, muddy contrast) so performing a hard rail-to-rail voltage reset forces all the particles up and then down, and gives you a clean slate.
Versus someone drawing on the screen with a lot of zooming and panning. People with the tablet would notice that when they stop a series of these actions that were back to back, the screen will "clean" itself after about 5 seconds of idleness.
I have a question, hope it's not too sensitive, how do you guy protect your secret waveform ? One with enough tool and determination can just measure voltage at pixel and reverse the whole thing, the chinese can do that in less than a week i bet.
But I was too lazy and/or uninterested to attempt low level tinkering with e-paper myself and these days you can finally purchase some reasonably(ish) fast panels off the shelf.
But still, that does not prevent one from measuring the voltage directly at pixel.
[1]: https://github.com/prashnts/betty-epd/blob/master/notebooks/...
eInk mostly fixed the calibration issue years ago before the first eink monitors came out, and most eink products these days use beefier graphics processors.
It is my understanding (but I'm not even remotely an expert) that e-paper panels can suffer from permanent display burn due to the charged ink particles sticking to the glass. The stock waveforms take this into account and prevent it from happening. However I'm not entirely clear on the low level details or if this only applies to some subset of panels or etc.
Also when pushing for high refresh rate, you may need to use higher voltage, to make the droplets rise/fall faster. But sometime, those droplets are driven too hard and kind of stuck forever, so yeah, that's a trade off.
Sounds like a battery, or maybe even a dishwasher.