e-Ink and other paper like displays

I have periodically reviewed the e-Ink market looking for usable products w ithout a lot of experimentation. Most of what I find are displays without driver boards, a few high priced combos of displays with separate driver bo ards, but few docs and very few displays an driver boards with some sort of docs and/or library support. The one thing that always seems to be missin g is an easy to find and easy to read document describing exactly what they will do and what they won't do. Mostly the docs are a couple of poorly ma de videos with no real explanation.

I saw one video (don't recall the vendor or site) showing a display with pa rtial updates such as would be needed for a display of a real time device s uch as a... ventilator for example. That looks promising. But the display is monochrome and I still didn't find any docs on exactly how it would be interfaced to a system.

My main interest in them is to provide a display optimally viewable in any lighting.

There seems to be more than one manufacturer of these displays. When they are sold by third parties (mostly through Aliexpress) it is hard to tell wh ich brand of display they are. If I understand correctly one company owns the patents with multiple manufacturers licensing.

All of the inexpensive displays are pretty tiny. One maker includes touch screens even on 1.5 inch displays! My finger tip is not much smaller than that. The prices rise rapidly with size. A 4 inch display is pushing $40.

Anyone used any of these displays? Anyone happy with these displays? Tips ? Cautions?

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  Rick C. 

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Rick C
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I have only seen them on a couple of evaluation boards - I haven't had use of them myself.

The advantages of them are very low power, high resolution (if you want, and pay for it), and readability in sunlight. But they are /slow/. They are often too slow for "real time devices" - if you use e-ink for a digital clock, for example, it will feel sluggish on the seconds digits.

For good viewing in a wide range of lighting, also look at OLED displays. These can be very nice, high resolution, full colour, and give more brightness for the power than backlit LEDs. But no display technology is ideal for /all/ lighting conditions - there will always be some compromise.

Really, to test the display in different lighting, there is no substitute to getting some demo boards and looking at them.

Reply to
David Brown

ts without a lot of experimentation. Most of what I find are displays with out driver boards, a few high priced combos of displays with separate drive r boards, but few docs and very few displays an driver boards with some sor t of docs and/or library support. The one thing that always seems to be mi ssing is an easy to find and easy to read document describing exactly what they will do and what they won't do. Mostly the docs are a couple of poorl y made videos with no real explanation.

h partial updates such as would be needed for a display of a real time devi ce such as a... ventilator for example. That looks promising. But the dis play is monochrome and I still didn't find any docs on exactly how it would be interfaced to a system.

any lighting.

hey are sold by third parties (mostly through Aliexpress) it is hard to tel l which brand of display they are. If I understand correctly one company o wns the patents with multiple manufacturers licensing.

uch screens even on 1.5 inch displays! My finger tip is not much smaller t han that. The prices rise rapidly with size. A 4 inch display is pushing $40.

Tips? Cautions?

I recently saw a video of a display updating a value once per second. That 's not a problem unless you want to update the entire screen. They've had partial update for a while now. The three color displays are very slow req uiring many passes and many seconds to update the display.

It is not required to be highly visible in the dark. Just like paper exter nal light is required for eInk. Even so, I recently saw front lighted disp lays listed somewhere.

I don't need to do a look test on e-paper. It works. What I am looking fo r info on is how to drive them from an MCU. It used to be that a separate driver board was used since there are a few voltages that are required and some other details I don't fully understand. This time around I see the di splays from Adafruit which seem to combine that interface with the display. They aren't really commercial units though. They clearly gave no thought to how they might be mounted and I think they have components on the same side of the board as the display, or that may have been another company.

It's kind of weird that there is very little structure to the market. When you buy an MCU board they give lots of details and you know exactly who ma de each part and where to get good info on using it all. The eInk display products come from multiple display producers and they are not all the same at all. None of them provide very good support or documentation.

I remember once contacting one of the display makers asking for more detail s on building an interface for their units. They just told me all the info rmation was in the data sheet and that I should buy the controller boards.

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Rick C

Not as a developer, but I own a Kindle. Both contrast and readability are great, but refresh time is very slow compared to other technologies. Cool temperatures seem to increase this time even more. You also have traces of previously shown picture unless you do a full erase / redraw (which decreases refresh time even more).

If you want a display readable in varying conditions, maybe think of a VFD instead?

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Reply to
Queequeg

As well as the strange negative voltages they need very specific timings to drive the internal elements. Those timings are usually secret and proprietary to the display, and possibly damage it if you get them wrong.

You would need a CPLD or FPGA to act as a timing converter (TCON), but you can't build one because the timings are not published. Presumably Adafruit, Waveshare and friends have them under NDA and wrap them up in an easier package, but they're you're stuck with their PCB design.

The most standardised interface I've seen is the e-reader SoCs (eg iMX6SoloLite) which have a dedicated EPD controller. There is usually a firmware blob that provides the timing information - it is possible to download the firmware for an e-reader and extract the blob, but then you're on your own.

Waveshare are one of the better sources of providing interface modules and info, by the way:

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If you're Amazon building the next Kindle, you can get the info. They aren't interested in selling one-offs.

Theo

Reply to
Theo

I guess the technology has moved forward.

Front-lighting may be okay, but I think it would often be hard to get the angles right for an even lighting. Generally, e-Ink needs an external light source - if that's okay for the application, then great.

Fair enough. I'm afraid I can't be any help there - I haven't used them myself, and anything I could look up, you can look up too (and probably have). My general advice if the manufacturers are not giving good information would be to ask your favourite distributors for suggestions and data, but I expect you've thought of that already too! (And I am aware that the quality and helpfulness of distributors and FAE's varies a lot from country to country. We have several very good ones, but not everyone is that lucky.)

I've found Adafruit to be a useful source for one-off devices, such as screens to fit with rpi's for test benches, but not for larger numbers of units or for when you need to do a lot of work to use the devices.

I suspect that most e-Ink customers are huge - they can talk directly to the manufacturers, rather than having to use publicly available information.

Reply to
David Brown

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We discussed displays the other day and I mentioned the VFD as an option, b ut there seems to be some preference for an LCD. I think there would be mo re interest in the eInk if people were more familiar with them. Your exper ience with the Kindle was probably some time ago. Displays are faster now and smaller units are faster still, then partial display updates are even f aster yet.

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Rick C

I run a moving map program on a Kobo Glo (a nice Linux box, ~$50 on eBay). Some ghosting, but real-time updates of the map are quite acceptable. Fabulous screen outdoors in bright sunlight (this is in my plane).

The controller is a very complicated beast and not like LCD. An OEM module may not have adequate update rate for some applications.

Interesting stuff! Best Regards, Dave

Reply to
Dave Nadler

We may have talked about this before. When you say "plane" do you mean a glider? I have a faint recollection of talking to someone who used an e-Ink display in a very tight cockpit in a glider.

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Rick C

Yup, here's a short movie:

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Dave Nadler

Your cockpit shows exactly why I prefer the eInk display. It is more like the mechanical displays in visibility. The LCD display in the SN10B is much less visible.

I'm starting to think I need to get my hands on some hardware.

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Rick C

The SN10 LCD is transflective and sensitive to angle of view. In the video, SN10 is actually higher contrast than the eInk display. We encourage installation towards the top of the panel to improve contrast.

Always trade-offs. Let us know how you make out with the eInk display, Best Regards, Dave

PS: That video was taken of my former ArcusM cockpit a few years back. I and the airforce cadet in the back seat bailed out of my ArcusM in 2018.

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Please do not try this at home.

Reply to
Dave Nadler

Some time ago I came across a DIY project for a wireless fridge display using a small 2.13" e-Ink display from Waveshare. The display had an SPI connection and the project used a common ESP8226 board to control it. Apparently there's a library (GxEPD) for these displays.

I just looked that project up, the display is this one from Aliexpress:

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So it seems the library and driver board support part might be OK. Definitely expensive, that 2.13" is $20.69 while a 4.2" is $27.99. No idea if there's exhaustive documentation, with a quick look I'd say no. Also a consideration for a commercial product is that the GxEPD library has a GPL license.

Reply to
Anssi Saari

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Thanks for your post. I've looked at many display listings and they seldom have adequate info to judge them. They don't mention who makes the displa y or give a part number which is required for inserting it into a product. This is a Waveshare product which still does not make clear who makes the display, but at least is provides a reliable source.

I probably should get a unit and test it. This would not be a bad one to t ry. I have raspberry pis I could use. The listing does indicate Partial r efresh time: 0.3s. That's important. The software people keep talking abo ut 2x16 displays and using two because they can't fit all the data on one. So this display could provide 4x16 easily with 15 x 30 characters, much mo re clear than 5x7 LCDs.

I think I just talked myself into buying one to test.

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