1. E-ink requires a number of external components, even with their "chip on glass". In particular, E-ink requires a high voltage to change and charge the ink. I've seen inductors on most of these reference designs (ie: suggesting a boost converters of some kind).
2. E-Ink is very slow especially at this price range. Static images are fine, but don't expect animations.
3. E-ink protocols take a "temperature". In my cases, I've just been hard coding it to 25C / Room temperature, but this suggests that low-temperatures or high-temperatures may change the behavior of the screen.
4. E-ink is very "bursty" with power, using more power than LCD when changing images, but then zero power for most of its life. Be sure to think carefully about the current associated with this burst, especially if you're using 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). A slow-start circuit could solve this but you'd need to consider the longer charge times. Another method is to have 2x CR2032 cells in parallel, which lowers IR (parallel resistors lower resitance). I'd be most interested in studying the power-network of this design, I bet there's some interesting things going on here.
5. Most E-ink screens seem to be some kind of SPI protocol (4 wire). This is very similar to mini-LCD screens.
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LCD screens use more power, but get you color, more resolution, animation and seem to be cheaper still. Furthermore, LCD requires fewer external components (maybe a charge-pump set of capacitors, but some LCD screens don't even need that). Note that color/resolution/animation all costs processor power / storage / RAM, so be careful what you wish for.
LCD might be more suitable for beginners. But e-ink is very cool and awesome.
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".
I love it! On a somewhat related note, I've been working on a tiny Forth interpreter lately, and I think the e-ink device it could be an interesting choice to explore and test it on as a dedicated computational environment. Inkplate looks very appealing: https://soldered.com/product/inkplate-6plus-e-paper-display-...
You might want to check out Kagi to summarize articles: https://labs.kagi.com/ai/sum. It does the heavy lifting of producing nice outputs for you.
Not yet, sorry! It's still very fresh; I'll be releasing on GitHub pretty soon after cleaning it up a little and writing some documentation. When getting around to it I'll remember your comment and drop you a line.
Wow, haha, that's extensive. However, I'd urge you to release first and write docs later (or even release first and make it work later). I'd get a lot more value from code with no docs than no code at all!
Thanks for sharing the price. The build looks really good, but $400 is a bit steep for anybody on a budget. I think a good quality (high coverage and pixel density) LCD with auto-brightness would be economically competitive, though of course not really the same.
Look into memory reflective lcd's, doesn't look quite like e-ink (and for quite a few of them you have to resort to dithering instead of proper greyscale), but they're considerably cheaper and offer the same power benefits.
Additional benefit is that they're quick to refresh, if you have an application that requires it. I have a calculator built with it, works perfectly.
You can find this unit and other IT8951-based driver boards for it on a few different places/in different catalogs but Waveshare's easy and the price seems OK.
The ED133UT2 is a Carta 1200 display. The latest Carta gen is the 1250, but AIUI it's only relevant for color displays with the change being a thinner film that allow plastic color filters to be closer to the ink to improve contrast. I think the current greyscale 13.3" offered by E Ink's direct shop for $449 sans driver is still a 1200 - at least many vendors list VB3300-NCB as just an alternate name for the ED133UT2. The Carta range of displays are well-known from Amazon's Kindle and many other reader products, so my newspaper is basically a big honking DIY Kindle.
They also offer a 10.3" panel with even higher resolution for half the price of the 13.3" that's supported by the same controller and should be fantastic for all sorts of home dashboards.
While cobbling together my project I was really tempted to go custom PCB with the ESP and the ITE controller on one board. Looks like this eschews the seperate controller entirely and instead uses ESP32 PSRAM for the framebuffer and has the driving waveforms embedded in the MCU firmware etc. Very neat, also one further level of "go deeper", would love to try one!
This seems to be pretty common with E Ink displays unfortunately (you hear the same about many commercial ebook readers). At least the larger ones are more or less all from the same manufacturer (E Ink). I don't know if there is binning going on and Amazon gets better batches than Waveshare does ...
Direct sunlight can also be a big problem for this display tech, so I'm intentionally hanging it on a wall facing away from the most intense daytime sunlight I get.
I saw something like this a couple of years ago and wanted to do it myself. However the cost was relatively unattainable at the time, I'm glad to see it is getting more affordable!
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]
This is an LCD screen with active-power measured in micro-amps. This means that memory-lcd is more power-efficient than e-ink even if it updates once every 5 minutes. (though the less you update, the better e-ink gets).
If I’m not mistaken yes the power does go. I have a smartwatch with a 30day+ battery life (Amazfit Bip) which also uses I believe the same type of display.
It’s ~somewhat similar to a calculator 8 segment display in operation - low power, low resolution/pixel density, can be inverted etc. Or maybe old gameboys perhaps?
I’m cautiously optimistic, because two decades is the lifespan of a patent. E Ink the company has been a terrible steward of the technology. May they lose their state-sponsored monopoly and fade into irrelevance in peace.
People don't realize that e-ink and related technologies simply _don't sell_, and rather make up crazy conspiracy theories about eInk for some reason sabotaging their own product.
Consumers don't accept the disadvantages of eInk, such as the low refresh rate, the apparent low contrast, and the extremely poor color reproduction. At the same time, the advantages are rather minuscule; in fact, people have a hard time distinguishing eInk from reflective LCD. They think reflective display == eInk, while in truth many devices popularly seen as "eInk" are actually reflective LCDs (e.g. the Pebble and Garmin smartwatches).
Most companies that have made non-LCD based products are simply out-sold by LCD products and go bankrupt. I could probably name half-a-dozen non-LCD reflective technologies which are dead today without even checking Wikipedia, like Gyricon, Mirasol, the stuff the OLPC used, Flepia, etc. All of them dead or niche.
You just can't point fingers at eInk since some of these technologies faded even before eInk even existed, and some of them are owned by companies which are at least ten times larger than eInk (Qualcomm, Fujitsu, etc.). These theories claiming that eInk is the large neighborhood bully just don't many any sense whatsoever. Qualcomm, for example, _is_ a well-known bully; unlikely to be scared of eInk's portfolio. But Qualcomm released exactly 1 product with Mirasol - which completely flopped in the market - and then gave up on it.
Even price displays are usually LCDs, with only a minority being eInk, but as you can see here, casual hackers have a hard time distinguishing between them.
The small displays they put on smartcards (showing a 2FA or the like) are also LCDs, and even with a practically minuscule battery they last for half a decade, and that's refreshing itself once per hour... I couldn't think of a better usecase for eInk, and yet it fails to beat a much cheaper plain old LCD, save for perhaps if you wear polarizing glasses...
> make up crazy conspiracy theories about eInk for some reason sabotaging their own product.
Why do people make up crazy stories about banks conspiring with the bond-rating agencies to sell bogus financial products to their clients, oltimately crashing the entire market and driving themselves into bancrupsy. I mean, no rational person would do such a thing!
I talked to someone building related tech in the industry and E-Ink the company has a stranglehold on suppliers and leverages that to force compliance despite the patent nearing expiration (blocking anyone else from getting access to those suppliers).
The patent has allowed them to become entrenched and all current suppliers to depend on them. This will be hard to correct even with patent expiration.
I don't remember the specific details (unfortunately) and it's second hand info, but I was disappointed to hear it from someone more involved than I.
E-Ink is apparently engaged in anti-competitive practices. Why should it matter that the market in question is small?
Lots of companies do this. Amazon demands exclusivity for certain book sales, and they have contracts with sellers that make it hard for other marketplaces to undercut them. Qualcomm is famous for abusive practices. The list goes on.
In general, IMO companies should be able to compete by offering a superior product and/or a superior price point and/or a superior experience. They should not be able to compete by getting in each others’ way.
You are of course correct. The far bigger core problem is that our government is generally captured and does not serve one of its core purposes, enforcing competition, i.e. preventing manipulation of markets. A way that a legitimate and constitutional government would do such a thing, would be, e.g., require competitive practices, e.g., e-ink screens must be sold to anyone so wants to buy them at fair price, to put in end products … if the company e-ink wishes to engage in interstate commerce, which is supposed to be regulated by Congress.
However, because Congress and the whole government is inherently illegitimate as is easily objectively measured by its constant, frequent, and persistent failure to abide by the constitution; things like industry capture of government and fraudulent regulatory bodies, is now the norm.
> E-ink should be, but it never seems to get there. T
Every price tag at my local grocery store is eInk. Like there must be thousands. I'm guessing there are updated by wifi. I mean that is pretty damn good use and the refresh rate means you saw real energy over LCD.
Funny you should bring this up, I just thought about it today what a terrible development those electronic price tags are from a consumer perspective. Because of course the next step is constantly changing the prices based on customer data telling them how to extract the maximum amount of cash from shoppers. Which is what I noticed at stores where they do have them, in extreme cases they change the prices of some products multiple times a day.
My neighbor is quoted substantially lower prices on the same car sharing app as me, for the exact same cars. I don't know if it's the sole reason but she has a really old smartphone. Actually surprised me she can even still run the app on it.
The phone is maybe possibly part of it but most of actuarial calculations for car rentals are more based around age/zip code/sex and whatever driving history they can find on you than anything else.
Meanwhile in real world, the local grocery store can't even notice when products on their shelves have already expired. Sometimes by quite a long while. Not going to hold my breath for that one.
Maybe for you. But the first Kindle came out in 2007, and Amazon has sold tens of millions of them. The latest, the Kindle Scribe, even allows users to write in books with a pen.
I have an e-ink tablet (Boox Tab X), which is like a Kindle Scribe except it's also a (more or less) full featured Android tablet.
I have a very nice setup with Zotero, where I can sync papers I want to read to the tablet (running Zoo for Zotero), read and mark them up, and then sync the marked up version back to my computer.
I'm very interested in those Boox tablets.
Is there a way to have them display a static image (a custom website or Android app) when they are in standby? Or do they force-switch to some screen saver mode, like many e-readers do?
I've been using it since my previous job bought me a Sony PRS-505 (a co-worker got an Amazon Kindle).
Works well, w/ great battery life, and it really has come into its own w/ the new Kindle Scribe --- a large screen e-ink device which works as an e-reader and has useful note-taking and annotation capabilities (looking forward to seeing what competitors do w/ it --- probably would have bought an Onyx Tab Ultra if the Scribe hadn't been available).
I'd really like to see an affordable display suited to a Raspberry Pi, ideally w/ touch.
I use Onyx A4 reader and it has completely replaced paper for me. Making notes directly to PDFs while I read them is fantastic. And it saves my eyes. The only drawback is the price (around $1k). I am not watching videos on it though.
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.
> I don't know if they have batteries and wi-fi, or if they're updated manually with NFC
Yes, yes, yes, and other methods. These are called "Electronic Shelf Labels", and there's a whole slew of competitors.
WiFi is very high power, so its "pull only twice a day" kinda setup. You have a radio that only turns on twice a day to contact the server. Zigbee is also a solution, though that requires a Zigbee router (coordinator? I forget the terminology). Much less power on Zigbee, but if you're deploying hundreds/thousands of these ESLs, I think the benefits of Zigbee low power outweigh the penalties.
NFC exists but I don't think I've ever seen them in person. Probably too much effort since it'd require a human walking around the store?
I've even seen ESLs that work off of infrared. You're supposed to install IR LEDs all around the store, and they can it all shelf-labels to update. IR receivers are the lowest power, so this is the only way you can feasibly "push" data to a shelf label. (Wifi and Zigbee are "pull only").
So some computer blasts the IR signal around the whole store, which is enough information to transmit to change all the prices apparently. Like a giant broadcast remote control.
There was some information only recently on HN about reversing those Electron Shelf Labels [0] that was quite interesting, but your comment makes me wonder if you could eavesdrop these wifi price updates in such stores. Also, searching for that term on HN gives some other fun projects.
Ive seen similar (maybe the same) red black eink screens at best buy in the usa for pricing labels as well over the last year, so they're not exclusive to north of the border. Far fewer labels than a grocery store though.
> 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.
By the way, for the e-ink project I just linked in the other comment I ended up discovering the RV-3028-C7 RTC module. Idle power draw 45 nA at 3.3V instead of 110 μA for the DS3231 for similar functionality and ±1 ppm accuracy with an internally sealed oscillator. Awesome for battery-powered stuff and cheaper at low qty on Digikey.
I hope more of those little DIY/maker breakout boards adopt it. Pimoroni sells one. The one in my project is a free sample dev board that Micro Crystal sent me on request - which I guess is working out for them considering I just shared their product with you all.
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?
Your comment made me curious, but after looking at a teardown blog the 13" Dasung Paperlike uses the same ED133UT2 panel by E Ink as in my DIY newspaper project, which is a panel originally released about 2016/2017.
That said getting good partial refresh performance out of a panel like this requires a good controller and good code (after having written a driver for one such controller recently), and developers and product integrators have gotten more refined at this. Refresh speed and display quality are still a trade-off here though, expressed as different waveforms when driving the same display.
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...
Hopefully that answers any questions you have. You might need to research some other bits of knowledge to build up your base EE skillset, but once you're able to read those documents + understand them, I think you'll be in a good spot.
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.
Really the "hidden story" is the pimoroni board is like "ten bucks" whereas two years ago the exact same application was available from Adafruit for "fifty bucks".
I have two of the adafruit variety and it works fine with circuitpython and all that.
Someday the "wifi connected eink screen" will drop to maybe five dollars and that will be interesting in the market, open up some product ideas.
The adafruit product uses most of its power sleeping and occasionally waking up to check the wifi in the apps I played with, the screen itself doesn't use much power. I suppose it depends how often you want to refresh.
An example of interesting/weird apps for this technology is we're already at the point where its probably cheaper if you want a remote thermometer displaying on your wall to skip owning an actual thermometer and just display some web API of the current airport temperature or whatever. I wouldn't invest in consumer grade high resolution temperature sensors, you can replace all of that with a little wifi traffic right now and it's only going to get 'worse'.
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.
Tangent off your tangent: Do you have one hose at each pump at your gas station and you just select which grade of fuel you want? I've never seen that before. In the UK they have multiple hoses, and you choose which one by picking up the right hose.
Not the commenter you asked, but in the United States pumps with one hose are common. All the grades of petrol are dispensed through the same hose, and you just select which one you want.
Some pumps do have two (or more) hoses, especially those that have multiple types of fuel (one for regular petrol, and one for diesel). Some pumps for also have separate hoses for each grade, although they seem less common to me.
Sure, but after running all that RnD just about anything they make is reverse engineered immediately and perfect clones start being sold at rock bottom prices everywhere else. Whoever invests into extensive development with the intent to recoup costs via sales is the real sucker in this industry. Even official institutions like schools and universities rather order from aliexpress instead.
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 thought it as well, but then I bought a Kobo (Aura One back then) and I'm super happy. And it is much more hackable: there a countless patches to the official firmware, plus installing koreader is a piece of cake.
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
My smartwatch (or any similar transflective watch from the likes of Garmin or Amazfit for that matter) are similar. I got close to 90 days between charges once. Now I use it much more but still get many weeks between charges.
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.
I was reading on a normal android tablet. When I saw a sale on a kids bundle for 99 bux, decided to pull the trigger. Been my night time reader for months when going to sleep. It's amazing how easy on the eyes it is. I just read until I start to nod off.
Not OP, but it's both not as capable as LCD, and a lot of people who like reading seem to be part of the physical book sniffer religion. You know, the "I NEED A REAL BOOK." people. Given they're the main demographic aimed at by e-book readers, and a lot of them seem to hate even just the idea of reading on any screen, I can see why people would think the technology would quickly go away.
Isn't that like saying that iTunes MP3 purchasers are part of the 'vinyl obssessive' crowd? Someone who purchases a $14.99 book on a Kindle is doing so because they aren't going to spend $27.99 on the hardcover.
I wouldn't count vinyl as a real alternative to mp3's. mp3's are more a replacement for portable stuff : cd's and cassettes. And I never heard anybody but the most hipsters defend those.
It's more like comparing vinyl to first gen non-portable cd players. I wasn't there at the time, but I imagine it was probably not obvious then either that cd players were there to stay.
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.
It won't work as a badge out of the box, but if you know how to program an ESP32, it's easy to get it to use the demo libraries to load a JPG. It also has a touchscreen and 3 physical buttons for basic interactivity.
It's $85, so it's pricy for being used just as a badge, but it's a cool gadget that I use for a desktop display.
MiP aka Memory in Pixel is a great alternative to eink as well, well epaper, since to buy eink you'll be paying £££.
MiP supports animations/fast screen changes as well, but consumes a small amount of idle power vs epaper/eink none. For a badge I think this is acceptable, but it's also so, so hard to find displays as I think only Sharp makes them.
Looked into it a lot after owning a Pebble Time Round. I hate Apple for making consumers want a bright oled screen on a watch as the only option; sure, I charge my phone overnight & watch while I shower (bc I want the sleep tracking) but if I'm out and about/on holiday and my phone dies, I'd appreciate my watch still functioning as a fucking watch past the end of the day.
Plus smart watches look so much nicer when the screen is on all the time. To get my galaxy watch to last into the next day I run with the screen off, only wake on button press.
Cool little project, great gift for in-person team meetings!
Don't have much more to say except it's nice to see this kind of creativity still around in a world where everything has to sit on our phone and be served remotely from some megacorp's cloud.
My favourite e-ink application was in the Yotaphone II [1] some years ago, but sadly discontinued. I had one sent from the UK to Australia, where I was working for a few years. Reading books, docs or emails via the e-ink screen was a joy (no probs with bright sunshine), as was calling up your airline pass on the screen and turning off the phone, because the image on the back was retained. Even writing emails/docs was fine for me, despite the e-ink lag. I needed to charge it only every other day, and that still left plenty of margin. Best phone I ever had.
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...
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).
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.
I bought a badger2040 recently. I mainly wanted it for the ebook feature. A pocket-sized eInk device could make reading throughout the day so easy. I used to always have a paper book in my back pocket before phones.
Anyway, it's a great device with one small caveat. None of the GPIO pins are exposed, the only IO is buttons, usbc or a QT/Stemma connector. This would all be fine by me, except that there is only about 1mg of free space on the device. Doing any serious reading would require me to use external memory and without GPIO I can't do that. Making a few pins accessible would make attaching an SD card completely trivial.
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!
I built/assembled them. I carried out some informal experiments and found that it requires roughly one million full screen refreshes on two coin cells to completely drain them. Furthermore, given that Badger operates on an RP2040 and a battery holder comes with a toggle, it is astonishingly durable device. It is like a smoke detector, which can operate for a decade straight on a single battery.
Note: CR2032 is awesome and all, but be careful about extrapolating like this out to decade+ timeframes.
CR2032 only has 235mA-hrs of life down to 2V. x2 and that's only 470mA-hrs and 2V probably browns-out the circuit (so... 470mA is already a stretch. You'll probably get less than that on practice).
Over 10 Years, that's 5uA of power usage on the average.
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IIRC, an aluminum capacitor has ~15 uA of leakage current, and Tantalum is ~1uA of leakage current. So Aluminum caps are already disqualified, and Tantalum capacitor leakage-current already uses 20% of your power budget. Given the "Burstiness" of this workload, I know that these capacitors need to exist somewhere.
You probably can get a year out of this in practice. To get better than that, you'll need to spend an incredible amount of energy on finding every 1uA "leak" and plugging the leak.
And its crazy how many things leak 1uA. Not only capacitors leak 1uA, but so do MOSFETs, diodes (reverse bias currents, especially in schottky diodes)... diode-protected MOSFETs (oh no, twice the leakage!).
After I completed the project, I made a somewhat lighthearted personal vow to try to design a custom PCB next time I fall down the rabbit hole of hardware tinkering. I suspect, these days it is a commodity skills, and curious if you happen to have any suggestions or articles that could serve as a starting point?
PCBs are a dark art, and I focus on lower-speed (below 30 MHz) to try and avoid any issues.
I know that the faster the PCB is, the more issues you get. Above a certain frequency, inductors look like capacitors, capacitors look like inductors, and PCB-traces look like transmission lines with reflections and other such nonsense. Staying at a slower speed helps negate these issues.
Most application notes, be it from STMicro (for STM32) or Microchip, or really any other microcontroller manufacturerer, will have recommended hardware designs + their thought process fully documented.
Study up on the "reference designs". For ATMega328p, that's Arduino Uno. For more recent AVR chips (such as AVR DD), that's "AVR DD Curiosity Nano". (See schematics here: https://www.microchip.com/en-us/development-tool/EV72Y42A)
The sibling comment is too specialized, I feel. It depends on what you want to do. If you just want to connect a few components together, you can learn the required skills in a day, watch some KiCAD videos.
I made a sensor board the other day (I'm just printing the case for it now), and it was very enjoyable, and even came assembled for $1.7 per board:
> The sibling comment is too specialized, I feel. It depends on what you want to do. If you just want to connect a few components together, you can learn the required skills in a day, watch some KiCAD videos.
That's fair.
Lets put it this way: if your circuit works on a breadboard, you don't need to know anything about PCB design. The PCB will pretty much always be better than the breadboard.
Things get troublesome as you enter mixed-signal (analog + digital), or high-frequency.
Agreed, but you still need to know a ton of things that seem hard when you haven't done them before. Even exporting the Gerbers, or the BOM for assembly, or any of those things seemed too hard to me before I did it for the first time, so I don't want to underestimate people asking "I want to connect a few components into a custom PCB, how do I do it?".
> That has to cut down on the thickness as well since the Badger 2040 is designed to take AAA.
Would it be ok with the lower voltage of NIMH rechargeables? I really dislike primary batteries.
Edit: found the answer.
> 2x AAA rechargeable (NiMH) batteries only puts out 2.4V which is, strictly speaking, not enough for Badger. However, in our tests it keeps on truckin' down to an input voltage of 2.05V (without the LED), so if you want to use rechargeable batteries that should be fine.
AAAA is popular and as cost-effective as CR2032 (aka: bad value, but less-bad value than most other batteries of this size). Note that CR2032 is toxic, so AAAA is somewhat preferred.
AAA and AA have much more energy-per-dollar. I mean, so does lead-acid but I guess that's too big lol.
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Specialty batteries, like CR123A, seem to fit the bill for this size much better. But those are so, so much more expensive. I feel like the only two cells worth really considering are AAAA and CR2032, despite their deficiencies.
Exactly! The device is approximately 12mm thick. I will upload a side shot shortly. I appreciate you bringing this up, it's an excellent point! To be honest, it is still a bit thicker than I had initially hoped for; however, when I weighed my options - solder 26 devices by hand vs use pre-made components -- the decision was much more clear.
Badger comes with a built-in Qwiic / STEMMA QC connector. I believe it should work out of the box with Adafruit ST25DV16K I2C RFID: https://www.adafruit.com/product/4701
1. E-ink requires a number of external components, even with their "chip on glass". In particular, E-ink requires a high voltage to change and charge the ink. I've seen inductors on most of these reference designs (ie: suggesting a boost converters of some kind).
2. E-Ink is very slow especially at this price range. Static images are fine, but don't expect animations.
3. E-ink protocols take a "temperature". In my cases, I've just been hard coding it to 25C / Room temperature, but this suggests that low-temperatures or high-temperatures may change the behavior of the screen.
4. E-ink is very "bursty" with power, using more power than LCD when changing images, but then zero power for most of its life. Be sure to think carefully about the current associated with this burst, especially if you're using 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). A slow-start circuit could solve this but you'd need to consider the longer charge times. Another method is to have 2x CR2032 cells in parallel, which lowers IR (parallel resistors lower resitance). I'd be most interested in studying the power-network of this design, I bet there's some interesting things going on here.
5. Most E-ink screens seem to be some kind of SPI protocol (4 wire). This is very similar to mini-LCD screens.
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LCD screens use more power, but get you color, more resolution, animation and seem to be cheaper still. Furthermore, LCD requires fewer external components (maybe a charge-pump set of capacitors, but some LCD screens don't even need that). Note that color/resolution/animation all costs processor power / storage / RAM, so be careful what you wish for.
LCD might be more suitable for beginners. But e-ink is very cool and awesome.