eInk or ePaper

[gnuarm]

I've been interested in eInk for some time now but the technology is not pushed the way other new stuff is.  I get the impression those who own the rights aren't interested in developing the applications and only want to license the technology to others.  These companies try to find custom display customers rather than provide a wide spectrum of displays the market can easily use in products. 

Like the 2x16 LCD display that is sold everywhere.  There's no ePaper equivalent that is easy to integrate into a product.  Instead there was nearly nothing until the last few years when a few units have appeared, but they nearly all are a two board solution.  Rather than give a specification for interfacing the display to your design using whatever technology you care to use, they want to sell you a board, so you end up with two boards, one with the display and one with the controller.  Goofy.

Then there are many types of displays with different details of capabilities.  Some provide partial refresh, others don't.  It is a confusing mess to anyone looking to use these devices. 

Then there is the power issue.  The display holds the last image drawn indefinitely.  But how much power does it take to draw images?  I've never gotten an answer on that.  The boards don't seem to provide that info.  Again, goofy. 

Am I wrong about this?  Is this info easily available and I'm just too slow to pick up on it?  I'm also confused by the different manufactures not making it clear which display is which technology so it is hard to compare between brands. 

It feels like the time is right for ePaper to start showing up in products, but they are still few and far between.  I'd like to have one for my thermostat as the LCD thing is very hard to read.  I've never liked LCDs much.  The contrast is just too low.

[rdl]

Something like this?

https://www.waveshare.com/product/displays/e-paper/2.9inch-e-paper-module.htm

They have a lot of other versions.

[gnuarm]

Something like this?

https://www.waveshare.com/product/displays/e-paper/2.9inch-e-paper-module.htm

They have a lot of other versions.

Yeah, I'm familiar with Waveshare, but their documentation really sucks and they make it very hard to know who's ePaper panel you are buying.  This module you link to, for example, says it works with rPi/Arduino, etc. but the wiki page is not so clear.  In fact, there is virtually no info in the data sheets.  It also doesn't tell you anything about the display itself and they often commingle information for multiple types of displays. 

They are ok if you just want to play with devices, but if you want to integrate it into a product, good luck!

[MarkMLl]

Something like this?

https://www.waveshare.com/product/displays/e-paper/2.9inch-e-paper-module.htm

They have a lot of other versions.

Could I just interject... I got one of their larger panels for experimentation purposes, and the office moggy demonstrated that the flexible interconnect is embarrassingly fragile.

I agree with OP's point about documentation, and I'd also suggest caution about making any assumptions about compatibility between variants.

and https://benkrasnow.blogspot.com/2017/10/fast-partial-refresh-on-42-e-paper.html are a useful focus.

MarkMLl

[gnuarm]

I've been watching the technology for some time now.  If that video is the one about rapid partial updates, I've seen that.  In the early days there were no good sources of driver chips and the display makers didn't provide adequate info to design your own.  I ended up being referred to a guy at a company working on a design for a display maker.  He would not share any details as they wanted to retain that as proprietary so they could sell the chips as an exclusive.  I just wanted to do the interface in an FPGA as it was already in my design rather than design in a chip which would be obsolete in a year or two. 

I'm really surprised the market has not really changed much.  You can at least get units to play with from various sources like Waveshare, as well as the display makers (for a lot more money), but it is not easy to get units that are intended for commercial use or better, info on your own direct interface to the display. 

[amyk]

EPDs are not that difficult to drive, especially if you only need black/white:

http://essentialscrap.com/eink/

Grayscale is not that much harder, and relies on timing to get the pixels in an intermediate shade:

https://hackaday.io/project/11537-nekocal-an-e-ink-calendar/log/72153-can-you-get-32-level-grayscale-out-of-an-e-ink-display

The manufacturer(s) try to keep the details secret but they are not hard to figure out. The basic operation of the device is well-understood.

[gnuarm]

EPDs are not that difficult to drive, especially if you only need black/white:

http://essentialscrap.com/eink/

Grayscale is not that much harder, and relies on timing to get the pixels in an intermediate shade:

https://hackaday.io/project/11537-nekocal-an-e-ink-calendar/log/72153-can-you-get-32-level-grayscale-out-of-an-e-ink-display

The manufacturer(s) try to keep the details secret but they are not hard to figure out. The basic operation of the device is well-understood.

That's what I don't get.  WHY would anyone want to hide the info on using your device if you aren't the guy making the driver board/chip or the driver board/chip makes your product less attractive. 

Unfortunately there must be more to it.  When I dug into this a year or two ago I found there were different display technologies with different characteristics.  One of the big ones was partial updates.  They clearly had displays that supported partial refresh and others that didn't, just as they have some that support grey scale and others that don't. 

The author of the page you link to even talks a bit about this. 

These waveforms are enough to get basic images onto the E-Ink panel. In reality the subject is a lot more complex: there are all kinds of temperature dependencies and various ways how to switch pixels as quickly and accurately as possible.

I guess the display vendors find this interface to be problematic for the general market, so they push you to use separate driver boards they know work ok. 

[pallav.aggarwal@gmail.com]

There are many e-paper suppliers now, I was searching for an e-paper display (circular one) for one of the projects and found many suppliers. The interface is pretty simple, for a small size, it's SPI for a larger one it's the parallel interface.

E-paper displays are mainly useful where you don't need to refresh content very often and you need the lowest power consumption possible.

Here is a list of e-paper display suppliers if your are interested: https://pallavaggarwal.in/2021/06/28/e-paper-display-suppliers/

You might also be interested to see how different displays consume power: https://pallavaggarwal.in/power-consumption-oled-graphic-tft-displays/

I hope the above information helps someone working on the e-paper displays.

[gnuarm]

Yes, if you are building a hobby project, there are many choices of suppliers.  It is hard to get good info on the display.  There are many details on temperature and other parameters when you use it professionally.  There are also many options for writing speed and being able to update portions of the display.  Every maker has different specs on these things and often have multiple product lines that are not well explained. 

For hobby work it's easy to pick a device and run with it.  For professional work it's a big job to research the many suppliers (without knowing who actually makes them) and find an optimal product.