The E-Ink Badge

I've recently built a little "automatic newspaper" home deco piece using a 13.3" e-ink display, mainly as an excuse to try out Rust on an ESP32:

https://imgur.com/a/PqkhdGd (edit: corrected link to album with finished pics)

This is using an IT8951 EPD controller I wrote a little Rust driver for, which indeed talks SPI, although its SPI frontend is really a quirky/leaky abstraction over an I80 interface so you have to e.g. do chip select using I80 semantics and send preambles and such. Still, pretty breezy overall.

Can confirm the power draw is of course "bursty" during the update. Also, yes, e-ink refresh times get slower in colder temps. e-ink refresh also works poorly in direct sunlight. The displays can also "dry out" from it and it can cause artifacts. But the envelope for normal operation is overall fairly good, certainly for home/indoor use.

There's a fair amount of manufacturing tolerance and during testing manufacturers will usually record preferred drive voltages for the individual unit, etc. It's quite important to configure software to make use this information for optimal performance.

I'm hoping it will run for about a year without recharging from that little 1100 mAh LiPo pouch at one update a day (the newspaper is rendered on a common home server RasPi using LuaLaTeX+Ghostscript and then retrieved over Wifi), having taken self-discharge into account.

For more du-jour hype points I'm considering using OpenAI on the backend to summarize articles down to size to fit the layout! Or make it do style transfer to "1870 newspaper".

> But e-ink is very cool and awesome.

E-ink should be, but it never seems to get there. Too low-contrast and/or too expensive. It's been a Real Soon Now technology for about two decades.

There was another persistent display technology - chomeric displays. They came from a company called Chomerics, which was acquired by Parker Hannefin, which dropped the product line. Almost everything about those has disappeared from the Web, except that the former factory is now a Superfund site.[1]

[1] https://cumulis.epa.gov/supercpad/CurSites/csitinfo.cfm?id=0...

One very widespread use of two-color (red and black) e-ink screens is grocery store price labels. They're everywhere in Canada, and they work great. Even the fine-print (price per 100g) is clearly readable.

I don't know if they have batteries and wi-fi, or if they're updated manually with NFC, but either way they can't be too expensive if there are 5000+ in every store. They're a bit smaller than the badges these guys made, but they might be a lot cheaper and easier to work with.

> 2. E-Ink is very slow especially at this price range. Static images are fine, but don't expect animations.

It's not so slow, you can even play Dino Game on Badger 2040: https://twitter.com/niu_tech/status/1598804559270486033

> Another method is to have 2x CR2032 cells in parallel, which lowers IR (parallel resistors lower resitance).

Don't do this. It will work for a short time, but this basically just drains one of the CR2032 cells dead.

The issue is that lithium cells have very little discharge slope, so by the time the two voltages equalize, one of the cells is about to die.

This is in contrast to alkaline batteries which have quite a bit of discharge slope, so the two batteries can equalize voltage with most of their battery life still remaining.

> small CR2032 coin cells (which have ~10 to ~100 ohms of internal resistance). A ~100mA draw on the charge inductor isn't out of the question (at 10-ohms, that's a voltage drop of 1V, which probably browns-out the RP2040).

n=1, but I'm using a single CR2032 with a Badger 2040 (same as OP) and a DS3231 in parallel and it works just fine down to ~2.8 volts.

Recently, I have come across some interesting developments in the e-ink space. Although I haven't had the opportunity to test DASUNG monitors myself, but I read positive reviews. It is impressive, these monitors have extremely fast refresh rate. Yes, they are pricy. I am intrigued if something has changed technologically?

First ; Gosh I wish I had the knowledge you have on electric transfrerence/resistance==ohms/volts

But given that coin discs input/output are heat-dependent based on your comment, and no knowledge, would it not be sound to place CR coin batts in a baffle of graphene-aero-gel which could be just mm thicc and shield them from said temp inflections? This would greatly increases life, and can be moulded and produced en-mass with little effort and minimal cost (especially if you encase batteries used in space flight etc - and one may use the non-conductive format to use aerogells as an extremely light and thin insulating layer for many a thing.

Imagine the ability to 'spray' an AeroGel sealant onto a component which is heat sensitive to its accuracy...

I can confirm that they start to act weird around high temperatures. Just exposing it to the sun for a few minutes on a hot day can make dots not transition correctly

For very small stuff, OLED displays are another possible alternative. Great contrast, and there's no backlight so you don't spend power on the "off" pixels.

You could start with SSD1306 (monochrome, 3.3V) and SSD1331 (16-bit color, boosted voltage required). They speak I2C and SPI, and have decent software support.

The cheap and cheerful ones are <=1" diagonally though, so you need to step off the happy path to find badge-sized ones.

Second the power draw on refresh - that surprised me for the projects I was using it with. Especially if you’re planning on any kind of animation or dynamic display, it can eat your power budget a whole lot faster than you were expecting.

Could you recommend any good similar size as well as functionality LCD for my personal project? Charging is not an issue (short term use), minimal equipment and clarity at screen are key requirements.

You can reuse a cheap old Kindle for "wifi connected eink screen", see e.g. my Kindle Dashboard (https://github.com/niutech/kindle-dashboard) or Kindle VNC (https://github.com/niutech/kindle-vnc).

> skip owning an actual thermometer

Doesn't that rely on you living next to someone else's thermometer that's published? My not very accurate setup gives me more than a degree just down my property line (~30m) largely because one end is next to a road and the other on lawn surrounded by trees. Albeit neither are proper meteorological stations so accuracy in that sense isn't even an option.

I publish a few readings but have never really looked into the exact accuracy of the https://www.uradmonitor.com/ sensors. My actions in response are pretty coarse so it doesn't matter a huge amount... PM10 goes over 300 and I close the doors and windows sort of thing.

Tangent: My gas station replaced grade-selection buttons and rate/volume/price LCDs with one huge (20") touchscreen. Unfortunately because of the distance, it's brighter than the overhead lights at night. No one thought to add a little brightness sensor to the several thousand dollar machine.

Eh, Adafruit is always 10x overpriced regardless of what they're selling. That's kind of their shtick.

$16 for a 296x128 eink display may be cheaper than it used to be but it's still not affordable enough for mass adoption for this kind of thing.

And I try to convince my family about it, but just cannot get it through to them that "kindle the tablet" and "kindle the ebook reader" are entirely unrelated products. What a terrible bit of branding.

I use my kindle all the time and I totally forget about charging it. Then suddenly it tells me it's low on battery and I remember "oh yeah, I've not charged this in like 3 months"

What other modern battery device has that many interactions/uses without needing near daily recharges? It's like magic

I will always take the opportunity to read without a backlight. It's a hugely noticeable difference on the eyes for me. I'm just glad I don't have to print out thousands of sheets of paper just to read documents comfortably any more.

Why did you think it was a fad? Just curious. Had you ever seen one in real life?

Apparently out of stock.

The linked badger 2040 (https://shop.pimoroni.com/products/badger-2040) is half the price and apparently in stock. TFA is a 3D printed case around that, and custom software for the badge. It's also powered by a more capable dual-core M0+, however wifi is lost.

E-ink in general?

I did a desk calendar that looks like an old Mac: https://github.com/EngineersNeedArt/SystemSix

I've ported the Dino Game to Badger 2040: https://github.com/niutech/dino-badger2040 and I am working on a chess game.

At the beginning of 2020, I worked on a project to create a status indicator for real life, to help people in the office communicate whether it's okay to interrupt them or not. We ended up using a Pimoroni Inky with Raspberry Pi to auto-sync calendar/Slack status - easy to work with and reasonably pretty.

Of course, we didn't have a chance to deploy it before the pandemic hit, but someday I'll come back to it...

Here's my teammate's writeup of the project, including photos/video: https://www.timmychiu.com/dash

Yes, I just got my Badger W few days ago and I'm pairing it with a temperature/humidity/CO2 sensor - I designed and 3D printed a bracket for it, I'm going to mount it on a wall in my kitchen. It's also going to show brief weather forecast and the current price of my energy tariff(it changes daily).

That's what it looks like(just assembled it today so I haven't written code for it yet): https://photos.app.goo.gl/NjdisB8PbfFiGgkk9

I have a badger2040, looping through a few different screens - one with a QR code pointing to my linkedin. The lack of integrated battery is annoying though - either you stick a potentially hazardous one to the back, or you're carrying around a bulky AAA enclosure.

You can use an I2C SD Card Module: http://www.technoblogy.com/show?3Y2L

or use zlib to compress text data: https://docs.micropython.org/en/latest/library/zlib.html

If you look at the back of the badger you'll see that we put a set of pads to solder to for GPIO!

It also has a "Qw/ST" connector (STEMMA + Qwiic) that exposes an I2C bus so is ideal for adding sensors, or you could bash on an IO expander for a heap more pins!

You might be interested in the Serial Wombat which can expose gpio as as I2C, for which it has pads on the back.

  https://www.serialwombat.com/