
Can you get 32 level grayscale out of an E-ink display? - userbinator
https://hackaday.io/project/11537-nekocal-an-e-ink-calendar/log/72153-can-you-get-32-level-grayscale-out-of-an-e-ink-display
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userbinator
E-inks are fundamentally analog, so theoretically you could have as many
shades of gray as your timing resolution allows, but basically all the
commercial controllers available abstract the display as a dumb framebuffer so
you can't really access their fundamental operation of "make this pixel
_slightly_ whiter or darker.

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dfox
That depends on what you exactly mean by "controller". The hardware controller
typicaly has capability of exposing selected pixels to essentially arbitrary
voltage level for specified amount of time and the framebuffer abstraction
happens on the driver level.

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userbinator
The majority of dev kits and modules available abstract away that level and
provide something not unlike a regular LCD where you just send it raster
images; the driving waveforms etc. which are needed to do effects like this
are abstracted away, and the details are kept secret.

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TeMPOraL
Any examples? I've only played with Waveshare screens/drivers a little, but
I'm pretty sure I saw the LUTs defining voltage levels and times on the "user
side", e.g. within the examples code. And from a YT video that shown how to
drive those screens at 3FPS (didn't try it myself yet), I assume those are
_the_ actual LUTs that convert abstractions into voltage control.

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ISL
Awesome; can't wait for better e-ink displays.

Anyone aware of reasonably affordable greyscale E-ink displays at or larger
than a piece of letter-paper?

There's an interesting thread from a year ago, but would love to know if
prices have dropped/availability increased.

[https://news.ycombinator.com/item?id=13771203](https://news.ycombinator.com/item?id=13771203)

~~~
beezle
I got a reMarkable as part of the original lot of buyers. Haven't had quite as
much time to use it as I'd like but can summarize:

-would like a little better contrast on the screen, though it does seem roughly on par with kindles and the like with lighting off

-epub generally works well

-full size (ie, letter) pdfs do require cropping unless your vision is superior. The on-device crop is fine for text only pdfs but recommend using an external cropper for pdfs that have charts. Going this route has made it possible to read Reviews of Moder Physics on the reMarkable without the need to squint.

-it could use a 20% speed bump. Some of this might be achieved in future software updates.

You can, of course, use it for its other intended purposes - note taking and
draw/sketching.

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dawnerd
Relevant: [https://youtu.be/MsbiO8EAsGw](https://youtu.be/MsbiO8EAsGw)

~~~
aphextron
Video capable (>30hz) color e-ink displays are on the way too
[https://www.youtube.com/watch?v=pqn2650CJYc](https://www.youtube.com/watch?v=pqn2650CJYc)

~~~
gravypod
I can't wait for a future where something like that makes it's way into a
reMarkable.

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stevekemp
That's pretty neat to see! ePaper displays are now starting to become quite
affordable. I recently bought a 400x300 pixel display for about €25.

Unfortunately my device has only "black & white", no shades of gray at all,
but I had a lot of fun working out how to drive it from a small MCU, without
running out of RAM.

[https://steve.fi/Hardware/d1-epaper/](https://steve.fi/Hardware/d1-epaper/)

~~~
stefanpie
I've recently picked up a e ink display with a simple passive interface board
(bc Im not used to working with flex cable yet) and realized that a popular
way to build the frame in the mcu memory then dump it to the board. Most hobby
mcus like the atemga328p have enough static memory to store whole frames of
images and then push the whole image to the display, but don't have enough
dynamic memory of you want to dynamicly render whole frames and then dump
them. So I think that's what you are referring to when you said your trying to
figure out how render the frames without running out of memory. My screen had
example code that would draw frames an push small windows of image data to the
screen to draw the different parts of a complete image.

The reason I bring this up is because I recently had the idea of using small
SPI flash memory chips to render the whoel.inage frame dynamicly. The SPI
memory chips look like a neat way to easily do this by hooking one up to a
small mcu and drawing the frame using the spi memory chop then dumping the
whole frame from the memory chip to the screen. I hope to oder some small DIPs
soon to experiment with and I thought it also might interest you as well.

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emj
Can you calculate it on the fly by doing a slower transfer to the display, I'm
guessing it already does double buffering?

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stefanpie
I'm not clear by what you mean; I'm new to the eink hardware scene and I don't
know a lot about graphics rendering or how duble buffering works. It seems
that from my understanding that you transfer the parts memory frame from the
mcu to the memory on the eink display driver then you call the display driver
to update the display and run the LUT tables and analog signals to do the
stuff with the ink based on the current memory on the eink driver. However I
am probably not right in some regards because not all eink displays have
drivers and this process might not be case for all eink displays or I'm just
misunderstanding how it works.

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Simulacra
Is it possible to combine an e-ink display with a tablet display? For example,
when your iPad is in sleep mode, it's a reader.

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alok-g
Not using E-Ink, but Pixel Qi attempted combining those:

[https://en.wikipedia.org/wiki/Pixel_Qi](https://en.wikipedia.org/wiki/Pixel_Qi)

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pasbesoin
Is this "transflective" concept and technology dead now (commercially, R&D,
etc.)? For a long time, I was waiting for a responsive display that I could
read like a piece of paper.

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alok-g
While I have not been following in detail anymore, I have not come across
anything significant.

Note though that making it paper-like requires just a reflective display.
Transreflective is needed only when it also needs to function as an emmissive
display or needs a backlight.

Reflective displays suffer from poor colors as the pixels get divided into RGB
areas, which is contrasting with a color print because the printer can put any
color ink anywhere. This is the reason E-Ink, and every other reflective
display has found it hard to develop good color.

I have longed for a responsive color, paper-like display for long also.

Mirasol was one promising technology for that (latest demos could get
excellent colors as it also did not need to subdivide pixel area into
different colors, as colors were created using interference). However, there
is no activity on mirasol for the last several years.

Note: I worked on mirasol for about seven years.

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wernsey
Very cool.

I recently got a Waveshare 4.2" e-paper for my Pi, and I've been playing
around with a variety of dithering algorithms to get it to display images.

The Floyd-Steinberg algorithm seems to bring out the most detail if you look
at the image from a distance, but ordered dithering (with the 8x8 Bayer matrix
from Wikipedia) gave me a better "retro computer" look that I was aiming for.

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iMark
All the years e-ink displays have been available in consumer products and
we're still only talking about 5 bit greyscale?

I gave up my Kindle as soon as 5 inch displays were available. I thought the
market would have made more progress by now.

~~~
userbinator
_I thought the market would have made more progress by now._

I believe the reason is that there are a lot of patents/IP around the core
technology, and it's owned by very few companies who essentially have a
monopoly on the market. This also explains the secrecy surrounding the "low-
level" details. As this article shows, you can definitely get more gray levels
by driving the display directly.

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fapjacks
Yes and it's also been somewhat notoriously difficult to actually _procure_
the damned things.

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rb808
Nice. Looks like my old HP48.

