I 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!
I 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.
I'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.
I 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!
This 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
Seth 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:
Business card CD ROM's were a nice idea in the day.....
.... trouble was they would often 'misfeed' when using a tray style CD Rom drive and jam in the mechanism, meaning you had to dismantle the drive to get the card out.
Understandably, this would quickly piss off people you gave the card to. This helped make the cards rather unpopular.
> 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
?? add relevant wifi/port to connect to a projector/projection glasses / laser projector[0]
3 old micro ibm hard drives combined into rgb color space / diy laser image projector[1] might be able provide a bigger picture without exceeding DIY credit card size. kinda depends on laser size.
Ummm... a smartphone internal projector module more compact than diy stack of ibm microdrives / laser.[2]
Well, using something related/similar to turing-complete correspondence:
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If it can fetch/display files from the internet, yes, it can run doom[5]. Or make use of curl, curl-doom[18]
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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).
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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].
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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].
Thanks! 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.
Only 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.
Interesting 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).
Think 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]
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...
Fair 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."
Prologium 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.
I'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.
love 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
If "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.
As 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.
__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.
Good 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
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