A Collin's Lab look at eInk

Originally published at: https://boingboing.net/2020/12/22/a-collins-lab-look-at-eink.html


For the early eInk devices we didn’t have a controller that could handle the update logic entirely on its own. A lot of it ended up in software (in my case in the Linux kernel of the Kindle). It was interesting because it meant us software devs got to see a lot of the details of how this worked.
Partial updates were implemented with a few commands then we sent a frame that pretended the screen was a different size than it really is, and formatted in a way not unlike a TV or VGA frame.
Gray scale images (4-bit in our case) was implemented through waveforms. Patterns of 0 and 1 values that when applied in sequence approximated the necessary voltage. To show an image we’d expand the 4-bits per pixel image into 8-bit bytes, then replace the values with a pattern. And finally the controller would issue the update in multiple passes, a single bit per pixel at a time.
Fun software problems are things like. Because the display retains an image even when it is powered off, how do you handle booting up seamlessly. Do you keep some memory (flash?) of what your last image was. Or do you require the same sequence of events of occur before powering off (of suspending), such as always displaying a blank screen or logo? Yes, that’s how the Kindle does it.


So cool to hear some of the details. Thanks!


Thank you for this! The very best feature of Make magazine (for me) was always Collin Cunningham. (the moribund link is still up). It’s all in the facial expressions, curious attire, tight video editing, and pure nerdification. So now one of the better reasons to visit adafruit and find him there.


Came here to say the same- Collin is immensely entertaining to watch. I miss his videos.


Disassembling the display’s film was a lot more difficult, and I ended up breaking it in half.

Which did work.

A man after my own heart.


Can someone smarter than me answer this? Is there any reason why a classic RGB display couldn’t be created by alternating pockets of polar RBG pigments in smaller cells? I understand that it would need the addition of B&W because it has no “native” black state and RGB coloration won’t create white with pigments. How about varying currents to attract pigments of different sizes at different rates to achieve blending?

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It’d probably be CYM rather than RGB, but I’m not 100% sure you could get (good) colors other than the pigment colors. The halftone or Ben Day processes that make the whole rainbow possible from three colors of dots rely on physical processes that don’t really apply here, namely rotating the grid of dots and varying the size of them. Plus you need black to make it look any good.


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