6 ms·
Muxcard, a DIY credit card size computer
Recent and related:
A self-powered computer in actual credit-card size (~1mm thick) - https://news.ycombinator.com/item?id=48251528 https://news.ycombinator.com/item?id=48251528 - May 2026 (11 comments)
- WithinReason 4mo agoCoincidentally, the xteink x4 has the same CPU, an e-paper screen and is close to credit card sized.
- NetMageSCW 4mo agoIf you think 1.33x1.28x7.76 times bigger is close to the same size. I don’t.
- gnabgib 4mo agoLast week (87 points, 7 comments) https://news.ycombinator.com/item?id=48251528 https://news.ycombinator.com/item?id=48251528
- dang 4mo agoThanks! This project is cool enough that I think we can tolerate another thread about it, especially since that post didn't get too much frontpage time. I'll put a link to it at the top though.
- dthdthdtejdz 4mo agoThanks! Arbitrary application of rules is nothing short of what I would expect from CCP LOVER DANG.
- gnabgib 4mo agoIs this an ops we shouldn't have put this dupe in the SCP, or an ops the original submission should have been a different URL?
- w8vY7ER 4mo agoyer dang right
- voidUpdate 4mo agoIt seems like it might be a little expensive for a business card...
- bird0861 4mo agoLet's see Paul Allen's card.
- yesbabyyes 4mo agoOr, it would be interesting to see how this would fare in American Psycho.
- asdefghyk 4mo agoThis post - the title made me remember ... ( as a credit card is about the same size as a business card ) A Linux Business Card CD is a miniature, credit-card-sized optical disc containing a stripped-down, bootable Linux operating system. They hold around 50MB to 100MB of data and were highly popular in the early-to-mid 2000s More info at https://en.wikipedia.org/wiki/Bootable_business_card https://en.wikipedia.org/wiki/Bootable_business_card
- hantusk 4mo agoyeah, also reminded me of wifi sd-cards: https://hackaday.com/2016/06/30/transcend-wifi-sd-card-is-a-tiny-linux-server/ https://hackaday.com/2016/06/30/transcend-wifi-sd-card-is-a-...
- mmmehulll 4mo agothis is really cool. I didn't know we had these
- WillAdams 4mo agoOr the Rex 6000 or other PCMCIA cards: https://en.wikipedia.org/wiki/REX_6000 https://en.wikipedia.org/wiki/REX_6000
- NetMageSCW 4mo agoI had one of those - I think it is still in my office desk.
- devmor 4mo agoThese things were cool! I believe I had some drivers installed via some of them, and a Kubuntu livecd.
- dredmorbius 4mo agoSeth Schoen (<https://news.ycombinator.com/user?id=schoen https://news.ycombinator.com/user?id=schoen> at HN) was lead dev in building one of the best-known instances of these, the Linuxcare Bootable Business Card (LNX-BBC), and has occasionally commented on that here: <https://hn.algolia.com/?dateRange=all&page=0&prefix=false&query=by%3Aschoen%20bootable&sort=byPopularity&type=comment https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...>
- ohlookcake 4mo agoCan it run DOOM?
- suzukivenom 4mo agolegendary
- rbanffy 4mo agoI would love if the screen could take up more space, even at the expense of a little extra thickness.
- jansan 4mo agoI think that there could be a wider screen if such formats are available. Once we have betavoltaic batteries, the entire card can be screen.
- rbanffy 4mo agoI'm not sure beta voltaics will ever reach LiPo densities. All materials I know would be unwise to place in your wallet, or anywhere near your body. If we are OK with a battery and a beta voltaic source, a tritium one is reasonably safe and can trickle charge the battery when the device is in deep low power mode. The battery can still be charged by the induction coil.
- WithinReason 4mo agoThat actually exists, with even the same CPU but no NFC: https://www.xteink.com/products/xteink-x4 https://www.xteink.com/products/xteink-x4
- rendaw 4mo agoThat looks like it's the size of a smartphone. It's 7 times thicker... I'm not sure that qualifies as a little thicker, plus all the other dimensions.
- goodpoint 4mo agoIt's not a computer.
- cbdevidal 4mo agoIt’s got more horsepower than my first desktop computer
- krauseler 4mo agoRight, it doesn't compute. Apologies for the lie.
- bigfishrunning 4mo agoIn what way is it not a computer?
- antonvs 4mo agoYour definition of "computer" is incorrect.
- mmmehulll 4mo agolove this. would be cool if we can see and perform all kinds of banking txns on this. Think ledger but all in one card. Super cool. Even cooler would be card to card money transfer without use of swipe machines
- resonious 4mo agoIf "ledger on card" interests you, then you might enjoy Japan's FeliCa cards. They store balance locally on the card so you can pay very quickly, no network required.
- abdullahkhalids 4mo agoDo these cards solve the electronic cash problem (in a completely different way than cryptocurrencies)? What I mean is that - Are the card readers special/trusted issued by bank/govt in some way? Or you can transfer money from one card to another yourself fully offline? - Is there any requirements that the transfers have to be eventually communicated to the bank by one of the parties to be fully resolved? - Has someone managed to create fake cards with fake money in it, or this is impossible by design?
- csande17 4mo agoAs I understand it, these cards work basically the same way as transit card systems in other countries, like the SF Bay Area's "Clipper" cards. The overall model is similar to tap-to-pay debit cards. They're only used for consumer-to-business payments. When you tap the card, the card sends over an account number / signature / etc, which the merchant sends to a central clearinghouse to finalize the transactions. The main difference is that the card itself keeps a running balance of how much money the customer has available to spend. In many cases, this gives the merchant enough confidence to e.g. let you through the train turnstile without actually waiting for the central clearinghouse to confirm the transaction. (I think in practice they usually send all the transactions in batches, daily or weekly or something.) The readers do some trusted-computing/secure-enclave type stuff but are not especially hard to obtain; I think there have even been cases where companies like Nintendo have built them into consumer products, so that you could e.g. tap your card to your Nintendo 3DS to buy a video game. I imagine there's a bit more security on the machines that let you load money on the cards, but it's probably not completely impossible to make a fake card. But the low value limit (usually a couple hundred dollars, depending on the card provider), the inability to get cash out of the system (often you can't even buy things like postage stamps), and the fact that you'll get caught relatively quickly (once the central clearinghouse notices the transactions don't match up) make it unattractive to do it in practice.
- fph 4mo agoHow do you recharge it? Do you have to swap the battery?
- krauseler 4mo agoHey, developer here :) I used an ultra thin LiPo, so you can actually charge it. USB is obviously not an option but it uses magnetic pogo pins on the back side ^^
- aa-jv 4mo agoI want this, but only for one thing: email. I already use an pwnagotchi, and it works great for this - but its a bit bulky. If I can get this set up and working, it'll be my main interface to email.
- thenthenthen 4mo agoDo yourself it!
- pslab 4mo ago[flagged]
- iberator 4mo agoRun Unix v6 on it :) 16 bit and works with like 80kb of ram
- dredmorbius 4mo agoFuzix might be another option: <https://fuzix.org/ https://fuzix.org/>. Works on the RISC-V 32-bit processor, sometimes.
- sargstuff 4mo agoEPS32-OS : https://github.com/ESP32DE/Boot-Linux-ESP32S3-Playground https://github.com/ESP32DE/Boot-Linux-ESP32S3-Playground
- cbdevidal 4mo agoWhat fun! I’d love to also go the opposite direction, a full-sized laptop with an ESP32 running tiny386 and Windows 95 ^_^ https://www.hackster.io/news/he-chunhui-s-tiny386-turns-the-humble-esp32-s3-into-a-fully-functional-386-powered-desktop-pc-5454cf6e36a1 https://www.hackster.io/news/he-chunhui-s-tiny386-turns-the-...
- c22 4mo agoThis could be great if the rest of the chassis was filled with batteries.
- sargstuff 4mo agodiy 486 schematics (around year 2000)[0]. no longer available. Discription/overview[3]. :( But, current linux doesn't support 486 cpus. Was turned into something commerical (?2002[2])[1]. Perhaps modern version would be the old AMD cyrix chips? ------------------------- [0] : http://boole.stanford.edu/cebit/ http://boole.stanford.edu/cebit/ [1] : https://megagames.com/news/matchbox-pc-smallest-world https://megagames.com/news/matchbox-pc-smallest-world [2] : https://ptacts.uspto.gov/ptacts/public-informations/petitions/1461491/download-documents?artifactId=7YAtsRNIfmLL5weHzCGyrL1kG8c8YD7GU8Q8pfUn2fmHFdtupkpjm6A https://ptacts.uspto.gov/ptacts/public-informations/petition... [3] : https://www.paloaltoonline.com/morgue/monthly/1999_May_26.MICRO.html https://www.paloaltoonline.com/morgue/monthly/1999_May_26.MI...
- mrbluecoat 4mo agoFirst thought: cool! Second thought: e-waste (same reaction as single-serve coffee pods, circa 2023)
- krauseler 4mo agoGood point. Ideally it would be the opposite of waste if it can save you from several cards. But banks would never certify such a multi-card system unless a big company pushes it forward. Otherwise I'm sure people might use this to hack some terminals :P
- sargstuff 4mo ago?? e-waste recycling ??
- krauseler 4mo agoDeveloper here :) Just saw this and love how I got the 100th or so "Does it run DOOM?". Even now officially an issue on GitHub. Does that mean I now have to deliver?
- Muhammad523 4mo ago> Does that mean I now have to deliver? Well, if you'd like to, you're free to do so! If not, somebody else could do it. You're not your audience's slave I know it was intended as a joke but still..
- IAmBroom 4mo agoSo... it's not DOOM-complete? Teenage Alan T. would be so disappointed... :D
- sargstuff 4mo agoWell, using something related/similar to turing-complete correspondence: ---- If it can fetch/display files from the internet, yes, it can run doom[5]. Or make use of curl, curl-doom[18] ----- stripped down doom can run in 4MB (doom on a smart toothbrush[7]). ESP32 has support for up to 4MB external PSRAM[1]. ESP32 port of doom[2]. lcd screen might provide for faster refresh / less blury images under magnifying glass. Alternatively, adding an expansion port to be able to use 'doomchip' might make it easier hide game play while at work[8] / stay awake between screen frame refreshes. (and/or simulateously play tetris & 1d pacman; add Badgey functionality[19] ) But should one go with micropython[3], reflectionsOS[4] or not waste space and use a 2 stage 512k bootloader for dns.doom[5]? contikiOS[6] for dns.doom[5] might be the correct fit without needing to add 4mb psram / doomchip expansion port(s). ----- Misc doomchip information: doomchip non-tech article(2020)[11]. doomchip developer comments[12]. Should be able to get at least 2fps! doomchip better expanded upon in a 'heads up, 7up' thread -> slice[9]/doomchip[10]. ---- Surprised there's no dns doom.wad / I.D.Software Application (IDSA) rfc "Spit.wad: A DNS string encoding using Unicode for doom.wad graphics" version of rfc3492: "Punycode: A bootstring encoding of Unicode for Internationalizaed Domain Names in Appliations" (IDNA) [13] (IDSA) rfc might permit formally unifying things like unicode-line-stacker[14], stacked diacretics generator[15], unicodeart[16] and "awesome symbols and characters in a bash prompt"[17]. ------------------------------------------------------------- [0] : "Can it run doom?" : https://canitrundoom.org/ https://canitrundoom.org/ [1] : https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/external-ram.html https://docs.espressif.com/projects/esp-idf/en/latest/esp32/... [2] : https://www.techeblog.com/doom-electronic-badge-emfcamp/ https://www.techeblog.com/doom-electronic-badge-emfcamp/ [3] : https://github.com/NoosaHydro/2.4inch_ESP32-2432S024/tree/main/cnd-micropython https://github.com/NoosaHydro/2.4inch_ESP32-2432S024/tree/ma... https://github.com/wojciech-graj/cydoomgeneric [4] : https://github.com/frankcohen/ReflectionsOS https://github.com/frankcohen/ReflectionsOS [5] : https://undercodetesting.com/dns-can-run-doom-how-2000-dns-records-became-a-covert-channel-for-malware-video/ https://undercodetesting.com/dns-can-run-doom-how-2000-dns-r... [6] : https://contiki-os.org/ https://contiki-os.org/ esp32 https://github.com/contiki-ng/contiki-ng/discussions/3022 [7] : doom on a smarth toothbrush : https://www.youtube.com/watch?v=cO-Are8053g https://www.youtube.com/watch?v=cO-Are8053g [8] : https://hackaday.com/2020/05/13/the-doom-chip/ https://hackaday.com/2020/05/13/the-doom-chip/ [9] : https://github.com/sylefeb/Silice https://github.com/sylefeb/Silice [10] : https://github.com/sylefeb/Silice/blob/master/projects/README.md https://github.com/sylefeb/Silice/blob/master/projects/READM... [11] : doomchip article : https://www.techeblog.com/doom-chip-game/ https://www.techeblog.com/doom-chip-game/ [12] : https://threadreaderapp.com/thread/1258808333265514497.html https://threadreaderapp.com/thread/1258808333265514497.html [13] : https://www.rfc-editor.org/info/rfc3492/ https://www.rfc-editor.org/info/rfc3492/ [14] : https://github.com/axesilo/unicode-line-stacker https://github.com/axesilo/unicode-line-stacker [15] : https://codepen.io/lingyloll/pen/ooMaYO https://codepen.io/lingyloll/pen/ooMaYO [16] : https://www.unicodeart.com/gallery/ https://www.unicodeart.com/gallery/ [17] : https://unix.stackexchange.com/questions/25903/awesome-symbols-and-characters-in-a-bash-prompt https://unix.stackexchange.com/questions/25903/awesome-symbo... [18] : https://codeberg.org/xsawyerx/curl-doom https://codeberg.org/xsawyerx/curl-doom [19] : https://memory-alpha.fandom.com/wiki/Badgey https://memory-alpha.fandom.com/wiki/Badgey
- stavros 4mo agoThis is great, and I love it, and I hate to be saying this, but it's not literally the size of a credit card, it's 0.2mm thicker.
- krauseler 4mo agoFair enough, but I acknowledged that and it's 0.24mm thicker if we want to be exact. Here's a quote from my Git Repo: "Official ISO7816 smartcards are specified at 0.76mm thickness, but many real-world cards slightly exceed this in practice. The target for this project was simple: Stay around ~1mm total thickness and preserve the illusion of a normal card."
- stavros 4mo agoHey, works for me, I just got OCD from the title's usage of the word "literally".
- flintenmuschi 4mo ago[flagged]
- inflam52 4mo agoI love these kind of projects. M5Stack Cardputer Zero launched on Kickstarter last week and already hit their goal https://www.kickstarter.com/projects/m5stack/cardputerzero https://www.kickstarter.com/projects/m5stack/cardputerzero
- sargstuff 4mo agoKiisu[0], credit card sized footprint computer with modular add-ons. ------------------------------------- [0] : https://github.com/kiisu-io/ https://github.com/kiisu-io/
- firesteelrain 4mo agoJust in time for DEFCON. We built many of these types of badges
- sargstuff 4mo agohttps://www.techeblog.com/doom-electronic-badge-emfcamp/ https://www.techeblog.com/doom-electronic-badge-emfcamp/
- frankest 4mo agoTry NGK EnerCera for battery.
- lxgr 4mo ago> A fully working computer that is literally the size of a credit card. Nit: A (chip) credit card is already a fully working computer :)
- ZiiS 4mo agoOnly if it is inside a specially designed radio field and with no independent IO. Feels like a battery and IO justify the 'fully working' differentiation.
- IAmBroom 4mo agoI've never heard a definition of a computer to include its power source. IO is of course required.
- sargstuff 4mo agoThink that was a early computation thing -> CRT memory[0][1] Perhaps the 'city block' heaters requiring similar sized AC condensors to provide control over Maxwell's daemon was the inspiration for the unix daemon process. Optical computing makes fuzzy computations so much easier -> outgassing[2] ------------------------------------------------------ [0] : https://spectrum.ieee.org/the-birth-of-ram https://spectrum.ieee.org/the-birth-of-ram [1] : https://bunkerofdoom.com/lit/CRT-scopes/CRT_memory/index.html https://bunkerofdoom.com/lit/CRT-scopes/CRT_memory/index.htm... [2] : https://spectrum.ieee.org/adhesive-outgassing-nasa-standards https://spectrum.ieee.org/adhesive-outgassing-nasa-standards
- lxgr 4mo agoInteresting philosophical question: Is a tower PC that's not plugged into anything (neither power nor a keyboard or monitor) a computer? Does computation happen if nobody can perceive it? And is a computer a computer even between two CPU cycles? > no independent IO I would challenge that! How is a smartcard different from a server in a qualitative sense? Both get all their I/O over the network. Some cards even have a display, fingerprint reader, or can blink an LED (the latter unfortunately only indiscriminately when powered up, not in response to any computation, I'm afraid).
- deleted 4mo ago[deleted]
- z3ugma 4mo agoHidden in here is the coolest part, that the author made flex PCBs at home
- swordlucky666 4mo ago[flagged]
- mabster 4mo agoI went to the page expecting to rant about how it's not actually credit card size because of the thickness and was for once pleasantly surprised! Kudos to the author! It looks great!
- ghrl 4mo agoI was thinking all that too and considering commenting about being sick of those credit card size claims, but after seeing the footage I am genuinely impressed. Great work there.
- krauseler 4mo agoLove how the point of this entire thing comes across!
- majorchord 4mo agoI'll be that guy I guess then... they stated on their page that credit cards are 0.8mm while the muxcard is 1mm and yet they still claim it is "literally the size of a credit card"... not to mention that they carved out an NFC card, not a credit card. Yes it's still impressive either way, I'm not debating that.
- mabster 4mo agoI did notice that difference too. But previous "credit card size" projects have all been several mm (as in couldn't fit a wallet designed for credit cards). So 1 mm is... pretty sweet!
- rendaw 4mo agoIt said that the specification states 0.8mm, but that many real world cards are thicker. Are credit cards actually 0.8mm?
- dayjaby 4mo agoDid we read the same text? He wrote 0.76mm.
- zb3 4mo ago__This__ is where all those trusted app parts should go - a smart card with e-ink display that can provide high security assurance level and where I won't mind that it's locked down because it has only one purpose. __Not__ to my smartphone, effectively preventing me from modifying the system in the name of security. A banking app can use a card like this and on the display I could for example see where a transaction would go and then I could accept it, possibly even with a biometric identification. This would enable me to keep my smartphone customizable and banking apps secure at the same time. [apologies for the rant]
- NetMageSCW 4mo agoAnd it would communicate using?
- zb3 4mo agoNFC, with the smartphone, but the smartphone would not need to be trusted, it would just relay encrypted + signed data.
- deckar01 4mo agoPrologium is depositing thin film solid state batteries onto flexible ceramic insulators. They have some demos of single cells that appear to be thinner than 1mm continuing to operate after bending in half. https://prologium.com/tech/core-technology/ https://prologium.com/tech/core-technology/
- acrophiliac 4mo agodyi = Do Yourself It?
- sargstuff 4mo agoselfie thing.
- realo 4mo agoVery cool! Love it... But... The battery is likely to be squeezed quite a bit after this is put in my wallet, and in my pocket. Lithium batteries do not like to be squeezed. They tend to signal their distress with some type of heat, usually accompanied with a small fire and probable smoke as well. A distressed battery is very insistent upon everyone to see it's state of mind...
- skavi 4mo agoThis is discussed in the post.
- deleted 4mo ago[deleted]
- utopiah 4mo agoA credit card with chip is a computer without power.
- aidenn0 4mo ago> For the first prototype, I soldered each wire individually... I salute you sir. Did you have a better solution for later versions?
- sargstuff 4mo agocad/stl/cnc related files for 'automated assembly' via 3d printing pcb[1] / pick-n-place machine[2][3] would be nice. Catchy, higher order point/fundamental theory of calculus application of "Move over cassette tapes, adhesive tape has memory, too"[4] ------------------------------------------------- [1] : "Making a 3d printed circuit board that works" : https://www.instructables.com/Make-a-3D-Printed-Circuit-Board-That-WORKS/ https://www.instructables.com/Make-a-3D-Printed-Circuit-Boar... [2] : pick-n-place machine : https://en.wikipedia.org/wiki/Pick-and-place_machine https://en.wikipedia.org/wiki/Pick-and-place_machine [3] : No solder! : https://www.electromaker.io/blog/article/affordable-pcb-prototyping-with-open-source-pick-and-place-machines https://www.electromaker.io/blog/article/affordable-pcb-prot... [4] : "Move over cassette tapes, adhesive tape has memory, too" " https://news.ycombinator.com/item?id=48161242 https://news.ycombinator.com/item?id=48161242
- victorbjorklund 4mo agoWow. This is actually credit card sized.
- sargstuff 4mo agoNice light computational module for huds device. Random search engine project pick:[0] Perhaps also basis for a table coaster 3d hologram[1] Adding to card thickness / modularity: pop-up hologram display.[2][3] projected keyboard/display[4] & gain ability to respond to text messages! -------------------------------------------------- [0] : https://www.instructables.com/Smart-Glasses-V2/ https://www.instructables.com/Smart-Glasses-V2/ [1] : https://www.youtube.com/watch?v=xHbQRcIWxC8 https://www.youtube.com/watch?v=xHbQRcIWxC8 [2] : https://www.youtube.com/watch?v=vRo8m_a6F54 https://www.youtube.com/watch?v=vRo8m_a6F54 [3] : https://www.youtube.com/watch?v=wM_Byrv9iBI https://www.youtube.com/watch?v=wM_Byrv9iBI [4] : https://www.youtube.com/watch?v=gTnHEzshdIQ https://www.youtube.com/watch?v=gTnHEzshdIQ