NFC

77 Articles

As Cheap As Chips: The MiFare Ultra Light Gets A Closer Look

June 26, 2024 by 7 Comments

If you take public transport in many of the world’s cities, your ticket will be an NFC card which you scan to gain access to the train or bus. These cards are disposable, so whatever technology they use must be astonishingly cheap. It’s one of these which [Ken Shirriff] has turned his microscope upon, a Montreal Métro ticket, and his examination of the MiFare Ultra Light it contains is well worth a read.

The cardboard surface can be stripped away from the card to reveal a plastic layer with a foil tuned circuit antenna. The chip itself is a barely-discernible dot in one corner. For those who like folksy measurements, smaller than a grain of salt. On it is an EEPROM to store its payload data, but perhaps the most interest lies in the support circuitry. As an NFC chip this has a lot of RF circuitry, as well as a charge pump to generate the extra voltages to charge the EEPROM. In both cases the use of switched capacitors plays a part in their construction, in the RF section to vary the load on the reader in order to transmit data.

He does a calculation on the cost of each chip, these are sold by the wafer with each wafer having around 100000 chips, and comes up with a cost-per-chip of about nine cents. Truly cheap as chips!

If NFC technology interests you, we’ve taken a deep dive into their antennas in the past.

Inside NFC

June 24, 2024 by 7 Comments

[Ken Shirriff] likes to take chips apart and this time his target is an NFC chip used in Montreal transit system tickets. As you might expect, the tickets are tiny, cheap, and don’t have any batteries. So how does it work?

The chip itself is tiny at 570 µm × 485 µm. [Ken] compares it to a grain of salt. The ticket has a thin plastic core with a comparatively giant antenna onboard.

Continue reading “Inside NFC” →

Mobile phone reading an NFC tag with information on a garden plant

NFC Puts A Stake In The Ground

August 15, 2023 by 21 Comments

Sometimes we have a new part or piece of tech that we want to use, and it feels like a solution looking for a problem. Upon first encountering NFC Tags, [nalanj] was looking for an application and thought they might make a great update to old-fashioned plant markers in a garden. Those are usually small and, being outside 24/7, the elements tend to wear away at what little information they hold.

traditional plant marker

[nalanj] used a freeform data structuring service called Cardinal to set up text information fields for each plant and even photos. Once a template has been created, every entry gets a unique URL that’s perfect for writing to an NFC tag. See the blog post on Cardinal’s site for the whole process, the thought behind the physical design of the NFC tag holder, and a great application of a pause in the 3D print to encapsulate the tags.

NFC tags are super hackable, though, so you don’t have to limit yourself to lookups in a plant database. Heck, you could throw away your door keys.

Adding Smart Watch Features To Vintage Casio

July 3, 2023 by 16 Comments

[Matteo] has been a fan of the Casio F-91W wristwatch virtually since its release in 1989. And not without good reason, either. The watch boasts reliable timekeeping and extremely long battery life thanks to a modern quartz crystal and has just about every feature needed in a watch such as an alarm and a timer. And, since it’s been in use since the 80s, it’s also a device built to last. The only thing that’s really missing from it, at least as far as [Matteo] was concerned, was a contactless payment ability.

Contactless systems use near-field communication (NFC) to remotely power a small chip via a radio antenna when in close proximity. All that’s really required for a system like this is to figure out a way to get a chip and an antenna and to place them inside a new device. [Matteo] scavenges the chip from a payment card, but then builds a new antenna by hand in order to ensure that it fits into the smaller watch face. Using a NanoVNA as an antenna analyzer he is able to recreate the performance of the original antenna setup in the smaller form factor and verify everything works before sealing it all up in a 3D-printed enclosure that sandwiches the watch.

There are a few reasons why using a contactless payment system with a watch like this, instead of relying on a smartwatch, might be preferential. For one, [Matteo] hopes to explore the idea that one of the physical buttons on the watch could be used to physically disable the device to reduce pickpocketing risk if needed. It’s also good to not have to buy the latest high-dollar tech gadget just for conveniences like this too, but we’ve seen in the past that it’s not too hard just to get these systems out of their cards in the first place.

Hacking A “Smart” Electric Toothbrush To Reset Its Usage Counter

May 27, 2023 by 46 Comments
The visible circuitry inside the brush head.
The visible circuitry inside the brush head.

Following the trend of stuffing more electronics in everyday devices, the new Philips Sonicare electric toothbrush that [Cyrill Künzi] purchased ended up having a ‘brush head replacement reminder’ feature that wasn’t simply a timer in the handle or base of the unit, but ended up involving an NFC chip embedded in every single brush head containing the usage timer for that particular head. Naturally, this asked for it to be solidly reverse-engineered and hacked.

The NFC chip inside the brush head turned out to be an NXP NTAG213, with the head happily communicating with the NFC reader in a smartphone and the NFC Tools app. This also revealed the memory layout and a few sections that had write access protected by a password, one of which was likely to be the counter. This turned out to be address 0x24, with a few experiments showing the 32-bit value at this address counting the seconds the brush head had been used.

Continue reading “Hacking A “Smart” Electric Toothbrush To Reset Its Usage Counter” →

NFC Antennas Have Other Uses

April 22, 2023 by 38 Comments

As NFC chips proliferate, so do the antennas they require for operation, and since many NFC-enabled items are single-use, this means there’s an opportunity to put them to other uses. It’s an avenue pursued by [Brother-live], as he strips the antennas from spent metro tickets and gets experimenting.

The antenna in an NFC-enabled card is a flexible PCB laminated between the plastic outer layers, with the tracks forming a coil round the outside of it. Using some solvent the cards can be easily separated and the antennas retrieved. Once the chip has been removed they can be cleaned up and soldered to, allowing wires to be connected.

What can you do with an NFC antenna? Not a huge amount as you can see in the (Russian language, English subtitles) video below the break, but he tries it as a not-very-good heating pad, a power harvesting antenna from NFC readers, and perhaps most promisingly, as the coil of a moving-coil speaker. We’re not sure how much effort would be worth making on that last front, but we think with a bit of care there might be room for audible improvement.

If you’ve ever been tempted to have a look at an NFC card, it’s a subject we’ve covered before.

Continue reading “NFC Antennas Have Other Uses” →

A grey smartphone sits inside a sleeve made of light brown wood veneer and a black felt interior.

Wooden Smartphone Sleeve Keeps You On Task

January 31, 2023 by 2 Comments

Smartphones are amazing tools, but sometimes they can be an equally amazing time suck. In an effort to minimize how much precious time goes down the drain, [Lance Pan and Zeynep Kirmiziyesil] decided to make a functional and beautiful smartphone sleeve to keep you on task.

Most modern smartphones have some form of Do Not Disturb mode available, but having the phone visible can still be an invitation for distraction. By tucking the phone into an accessible but less visible sleeve, one can reduce the visual trigger to be on the phone while keeping it handy in the even of an emergency.

Once in the sleeve, the NFC tag sandwiched between the felt and wood veneer triggers an automation to put the phone into Do Not Disturb mode. This hack looks like something that you could easily pull off in an afternoon and looks great which is always a winning combination in our book.

To see some more focus-oriented hacks, checkout the Pomodachi or this Offline E-Paper Typewriter.