103points · 9h ago

Show HN: PaperMono, e-ink fridge magnet shopping list with mobile web page

Fridge magnet shopping list on an M5Stack PaperMono (ESP32-S3, e-ink touchscreen), synced with a phone web app over Wi-Fi. Works offline, ~2,400 lines of C++.

This is a great wee device! BLE, Wi-Fi and LoRa on one board makes it flexible for way more than a shopping list, this is just what I built first. This firmware only uses Wi-Fi.

Fully vibe-coded with Claude Code, I didn't hand-write this. I wanted to see how Claude would get on with building something useful for a new hardware device.

As it's stuck to the fridge it's easy for the family to use, and it's already being used day to day which I'll admit is a first for a home built project like this

github.com·by seamus_c·9h ago

Discussion 51 comments

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Zaheer·6m ago

Saw this device going around on X that has a mic / speaker so you can just dictate things: https://zectrix.com/en/

Ordered one but haven't tried it out yet. Sharing in case other folks are looking at devices.

dgently7·59m ago

i built a similar app, but included more meal planning recipe management features and a "shopping mode" that goes section by section like this but just shows the next two things to grab as large clickable button as i found it annoying to fiddle with a list and checkboxes.

since its just got a simple api for adding new recipes its also easy for terminal based agents to add new stuff. its really solved the problem of the 20page prose about "why my way of cooking beans is so special" with the actual recipes hidden at the bottom thing.

we can also just snap a picture of a recipe in a regular cookbook to inject it.

then we mostly just need to pick what we want to eat that week and it does all the actual list building. we have a few special "recipies" for things we just buy every week as standards, milk etc. and the system knows which things are "staples" we probably already have in the house, flour etc.

I love the fridge magnet epaper idea from this though. especially for its potential during cooking to not need your phone or a tablet on the cooking surface

maxglute·58m ago

Neato. Every time I see a competent eink project, I remember how long it has taken to due licensing drama and how much I've aged and will age until full wall eink.

m101·3h ago

I think on the app you should have an auto sort for your local supermarket. I have a list of aisles that I go through on my route around and I ask an ai to sort my shopping list by that route through the supermarket.

zikduruqe·3h ago

You'd love the Grocery App for iOS and Apple Watch. It learns based on which items you check off on your grocery list and puts them in order.

I'm like a caveman hunting my prey using it. I'm in an out with no meandering around.

https://apps.apple.com/us/app/grocery-smart-shopping-list/id...

seamus_c·2h ago

You can sort the aisles manually in the app, and there's a (hacky) route to use AI to categorise new items into an aisle. It shouldn't be too hard to use AI to sort the aisles I'd guess

dgently7·56m ago

ive heard but not confirmed that some store chains have apis to tell you what asile to find something on, but i assume that would probably require upc info which would be an annoying extra level of specificity to need to track and manage. you just wanna write "corn chips" not... "mission brand corn chips in the 64oz bag"

schainks·1h ago

This is amazing! Please make a 10" or 12" version that can sit on a countertop. I want an at-a-glance food prep schedule that's always on, and am using a spare kindle to do this instead.

schnevets·4h ago

Pretty cool! I remembered having a brainstorming session with co-workers about all the cool use-cases for e-ink displays over a decade ago. A product precisely like this was definitely mentioned, as was conference room displays, data center cage information, Kanban-style sticky notes in manufacturing, dynamic game pieces, among others. You'd think simple displays like the PaperMono would be as cheap as bluetooth speakers by now, but I know there are some major patent restrictions.

I can tell you this conversation happened over a decade ago because LCD Touchscreens were still more expensive than e-ink at the time.

lp92·4h ago

Game pieces with integrated eink to track health/stats and other game relevent metrics would be an interesting application.

seamus_c·4h ago

That's a cool idea! There are small 1.54" e-ink screens, I wonder would it be possible to add an NFC chip and have them completely passive? (i.e. powered from the writer)

mlmonkey·3h ago

OOS: https://shop.m5stack.com/products/m5papermono-with-lora-nfc-... :-(

I was thinking of putting together a little "Anki" device for my kid using such a device. Anyone have any other ideas for a small eInk device that is programmable like this?

jmgao·1h ago

I've been on the mailing list for restocks for a month now :-(

This is the only device that I've found that has an e-ink display and an NFC chip that can read cards (there are a few with writable tags).

seamus_c·1h ago

Yeah it's a great combo of capabilities, decent as an ereader with Crosspoint too, similar to Xteink, etc.

wpm·1h ago

The Xteink might be a solid choice for that actually

joezydeco·1h ago

I just got mine and I think it has a lot of potential in the newer code forks that are showing up, like Tesseract

NDlurker·2h ago

Should be able to do this on an xteink x3 or x4. I had been half considering vibe coding a project like this

Evidlo·3h ago

Watchy Anki device might be fun. There are cheap Chinese clones as well.

shitsonothersid·2h ago

Neat! I have one better though:

https://en.wikipedia.org/wiki/Post-it_note

* Works during power outage

* No battery!

* Very few remote attacks possible

* Very little attack surface

* Accepts multiple input technologies (ink, crayon, and so on)

schainks·1h ago

A gentle breeze from a running child unsticks any sticky note we have anywhere, how do you deal with that?

seamus_c·2h ago

Fair ofc :) This is more intended as a tech demonstrator and a bit of fun, although we have been using it for the weekly shop..

HelloUsername·2h ago

> Post-it note

* Produces paper waste

* Easy to lose

* Clutter

* Limited space

* Can run out of stock

* Not searchable/reusable

mft_·2h ago

* not vibe-codeable

* unlikely to hit the front of HN

shitsonothersid·1h ago

paper waste < e-waste

loss is almost costless

ok, I give you that the lack of ctrl-f is a bad thing.

gister123·2h ago

Nice work. I did something similar with my Kindle scribe. It shows me widgets for my grocery list, home todos, one that cycles between local weather, and some quotes. And I can use the pen to add or check off items. All vibe coded!

broabprobe·1h ago

definitely first read this as 'PaperMario e-ink fridge magnet shopping list...'

ex-aws-dude·45m ago

> Fully vibe-coded with Claude Code

Lame, my interest drops to 0 whenever I find out a project is vibe-coded

Because why would I be impressed if I can just go prompt it myself?

If its vibe-coded its just another display of claude code's abilities, which its like...duh at this point

That means the only thing interesting is the idea itself, which in this case...

cush·3h ago

This would be cool if you could write on it with a stylus. I can’t imagine typing on my fridge - too clunky

seamus_c·3h ago

Yeah, it is clunky tbh. but it does work. That was the motivation behind the web UI. I also stuck a basic MCP in front of it, we sometimes use AI to help plan out meals for the week, etc.

Why keep it simple when you can massively over engineer it ;)

cush·3h ago

Haha true. This is why paper and pen are so hard to beat!

marksully·1h ago

It has microphone - you can dictate

edoceo·5h ago

I was just working on something similar. Was about to buy the xteink for my display. You've accelerated my progress. How's the battery life?

utopiah·4h ago

I'd check https://github.com/Josh-writes/microslate-firmware/ for the xteink as it is less focused on only reading, but keep in mind it's a screen only, so not touch. Buttons though are pretty good so enough for tick items on a list IMHO.

seamus_c·5h ago

Honestly it's pretty good, but it's too new to give you an actual number. I haven't had to think about it so far. As a LoRa Meshtastic node the device ran for days and still had plenty of battery.

In normal operation battery life is by how often you do a refresh, the rest of the time it's in deep sleep. I think for this application I could build in a refresh schedule tied to when the house is active (mornings, evenings, weekends) to reduce the number of refreshes. It syncs on touch if it hasn't synced in the last 5 minutes (and there's a button for when your feeling impatient)

hn1rig3rak·6h ago

Curious what you landed on for refresh, full flash or partial? Ticking off items one by one is exactly where partial update artifacts pile up on these panels.

seamus_c·6h ago

I stuck with the recommended full refresh every 15 interactions and partial otherwise. There's also a full refresh when moving from the settings screen back to the main list. Honestly though it probably makes sense to only do a full refresh when unticking (which is rare) or changing screens. The typical use cases are (1) glancing at the screen to make sure something is one the list and (2) ticking things off as they go into the basket. Neither really require a full refresh imho. Some ghosting is acceptable in general use I think

lucasrufkahr·6h ago

Hold on babe I gotta charge my fridge magnet…

Jokes aside this is cool

ex1fm3ta·5h ago

Project like this make me excited with AI. You can pretty much custom firmware, tailored for your specific needs. Thanks for this repo. Quick question to the community : why does nobody makes afordable huge e-ink displays ?

hansihe·4h ago

There is exactly one manufacturer of large EPDs, E Ink Corporation.

A few have tried to compete over the years, none have really managed to ramp up production and compete from my understanding. I believe there are some chinese firms making smaller panels now, mainly used in electronic shelf labels for stores.

From my understanding most of the patents for the foundational tech have expired at this point. I believe the panels are just generally very difficult to make, with difficulty ramping up further as panel size goes up, presumably the yield is fairly low.

seamus_c·4h ago

That was part of the motivation here: If I can think it up, can AI actually build it, even when it's outside my day-to-day experience? (and can it do it without frying the hardware somehow)

j45·5h ago

The last time I checked, patents.

otherme123·4h ago

Key eink patents are expired since c. 2017. But they bought potential competitors and keep innovating (and patenting), so the monopoly stays strong. If someone entered the market right now, with 2000 eink tech, and pricing at very low margin prices, they will go bankrupt: would you buy a 20" screen, no touch, ~70 ppp, refresh around 2 seconds for maybe $300? Also, patents might have expired, but key tech, such as precise micro-sphere manufacturing, is not under patent protection, but under trade secrecy: on top of old tech, it would be unreliable. Some like Zhiwei specialize in epaper for tags using old tech, but only for b2b and barely below Eink prices.

Competition explores completely different technologies: Daylight DC-1, Reinkstone, ChLCD e.g. from Iris... but either the tech isn't good enough to generalize or be cheap (the later), or the niche economics don't allow the inventors to keep investing (the two first).

Palomides·5h ago

there's no secret, they're just expensive to manufacture

jader201·6h ago

At first I thought “that’s a very specific shopping list for fridge magnets”. :)

ocd·3h ago

Much more advanced than what I use for this, but I use a small palm size drawing tablet with a magnet back from a Japanese stationery company called KING JIM. It's called the KING JIM BB-12. It was like $15-20, and I find it practical for quick jotting and as for my grocery list I can easily tuck away in any pocket.

I think there's something to be said about not carrying a phone-like device into stores, since the whole "cameras everywhere" situation is feeling more dystopian than it already did. I even carried paper lists to not further contribute to that.

drumhead·4h ago

This is giving me Juicero vibes.

nouveaux·4h ago

I think open source code would sit in the opposite end of the spectrum to Juicero.

idiotsecant·3h ago

That's a neat project and cool hardware but it's almost effectively paper, right? Slightly harder to use paper?

leipert·2h ago

Well. It’s synced paper. If I am on the go, i cannot check the paper on the fridge.

bozhark·2h ago

This would be great as something I can load the groceries to, then have the recipe and steps when making stuff

I hate using my phone for that stuff as it’s usually doing a few things and messy hands/ scrolling stuff is awful