Out of curiosity, if you have 75Hz but you're refreshing sparingly (e.g. you're in VSCode writing, unless you're scrolling, most pixels remain unchanged), wouldn't e-ink remain power-efficient?

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dredmorbius 5 days ago | parent | next [-]

Probably. E-ink drivers ("waveforms" is, I believe, the term of art) frequently target refreshes only at the portion of the display that has updated, using rectangles or other more-specific geometries to limit that area.

For text updates, where there's literally a cursor which moves at typing speeds, update frequency is quite low. Where you're updating or paging through documents, paginated navigation (where the whole screen refreshes at once, then remains unchanged for several seconds to minutes or longer) is quite efficient.

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teucris 5 days ago | parent | prev [-]

That requires the operating system to “hint” to the display that there’s no refresh necessary and for the display to shut down during those times. That’s currently not supported as these kits just take a video signal, but it’s something being worked on for a future version!

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ahartmetz 5 days ago | parent | next [-]

Edit: You work on that stuff, right? Then this armchair experting feels silly, just imagine it's for other readers.

It seems much more practical (if a little less power-efficient) to implement the no diff -> no refresh logic for screen regions in the display hardware. The RAM and logic for a display-side framebuffer can't be expensive today, a couple of Euros for the extra board space and chip(s). If that stuff takes off, just additional transistors in the all-in-one ASIC.

For the whole screen, that more or less already exists in laptop hardware: "panel self-refresh". HDMI and DiplayPort might need a new extension or something? Is there anything?

	▲	wtallis 5 days ago \| parent \| next [-]
		The Embedded DisplayPort standard has had the panel self-refresh feature since 2011, and the partial update feature since ~2015. I found a press release from Parade in early 2017 for a TCON supporting the partial refresh feature. I don't think there's anything missing from the ecosystem other than a strong impetus to use those features.
	▲	teucris 4 days ago \| parent \| prev [-]
		Yes! I work with the Modos team. You’re exactly right - ideally we want region-based refresh hinting. The SDK supports some region based features - we’d like to extend that functionality.

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vincnetas 5 days ago | parent | prev [-]

“Traditionally, the [e-paper display] controller used a single-state machine to control the entire panel, with only two states: static and updating,” says Modos cofounder Wenting Zhang. “Caster treats each pixel individually rather than as a whole panel, which allows localized control on the pixels.”