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The tiny chip that powers Montreal subway tickets

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Re: The tiny chip that powers Montreal subway tickets

#31

Post by gruez »

bboygravity wrote: post #29
kens wrote: post #25

Earlier quoted context omitted.

I don't like the e-waste aspect either, but realistically, the chip is so minuscule that the amount of waste is trivial compared to almost anything else you might discard. The chip is literally the size of a grain of salt. The other factor is that people who use tickets regularly would use the rechargeable plastic cards, rather than the disposable tickets, so the amount of waste is reduced.

The chip is the size of a grain of salt, but there's a relatively huge antenna inside made of conducting material (metal?) and glue and all that.

all of that is probably negligible compared to how much disposable foil is used for cooking or packaging.

Re: The tiny chip that powers Montreal subway tickets

#32

Post by amluto »

> Presumably, the makers thought that making the card look like a smart card would help people understand it. The card actually uses an entirely different technology.

It’s kind of the same, though. The physical communication layer is different, but the higher protocol layers are basically identical. Smart cards with contacts follow ISO 7816. These MIFARE contactless cards are ISO 14443 Type A cards, and their protocol follows ISO 7816-4.

This shouldn’t be terribly surprising — the entire ecosystem built for smart cards with contacts wants to support contactless cards with minimal changes, and this includes the host software, the readers, and the logic in the cards. There are even plenty of devices where the same device supports contact and contactless uses — plenty of credit cards, bank cards, and FIDO devices are like this.

This is analogous to WiFi and wired Ethernet. They’re have very different physical layers, but they are logically compatible, and the same software supports both.

Re: The tiny chip that powers Montreal subway tickets

#33

Post by lxgr »

> There are multiple NFC standards with differences in speed, protocol, and range, including NFC-A, NFC-B, NFC-C, NFC-F, and NFC-V. The MIFARE Ultralight cards use NFC-A, which is defined by the standard "ISO/IEC 14443 Type A".

Pet peeve: Calling these chips "NFC" is a bit misleading. NFC-A isn't defined by ISO 14443-A, but builds on it.

NFC is an umbrella standard that defines a way of storing structured data on a wide variety of existing contactless IC technologies (including, but not limited to ISO 14443) and products (such as NXP's various MIFARE chips, which in turn are based on various layers of ISO 14443 up to -4).

For the concrete example, it's correct to say that one possible implementation of an NFC-A tag is MIFARE Ultralight (that would be a NFC forum type 2 tag), but neither is NFC the only thing you can do with MIFARE Ultralight (and this transit use case almost certainly doesn't put an NDEF container on the ticket), nor is this the only type of tag you could use for NFC.

Re: The tiny chip that powers Montreal subway tickets

#34

Post by wkat4242 »

kens wrote: post #25
bobthepanda wrote: post #3

This wasn’t super obvious to me until later in the article but this is about the single use tickets. Neat stuff, though I can’t say I love the concept of e-waste NFC.

I don't like the e-waste aspect either, but realistically, the chip is so minuscule that the amount of waste is trivial compared to almost anything else you might discard. The chip is literally the size of a grain of salt. The other factor is that people who use tickets regularly would use the rechargeable plastic cards, rather than the disposable tickets, so the amount of waste is reduced.

Yeah but also the antenna and I wonder how many chemicals are used in the lithography process.

Re: The tiny chip that powers Montreal subway tickets

#35

Post by dheera »

bobthepanda wrote: post #3

This wasn’t super obvious to me until later in the article but this is about the single use tickets. Neat stuff, though I can’t say I love the concept of e-waste NFC.

I feel like 99% of people would not benefit from single use public transportation tickets. Even if you are a tourist, if you use public transportation once, there is a high likelihood you will use it multiple more times, in which case it makes sense to get a regular card. Most systems let you return the card and get the deposit back if you'd like.

Personally I collect the cards instead because I have a tendency to revisit cities years into the future. I just wish cities wouldn't make their cards expire so damn quickly. Wuhan's metro is nice, the cards don't expire until 10 years later. But I've found Singapore and Taipei expire within 3 years and you lose your stored money.

I have this "brick" of public transit cards for about 20 cities. It feels powerful. I kind of wish I could just swipe this brick in any city and just go. Unfortunately they all interfere with each other.

Re: The tiny chip that powers Montreal subway tickets

#36

Post by Waterluvian »

kens wrote: post #30
Waterluvian wrote: post #16

On the topic of NFC: my iPhone ApplePay thing taps so much more reliably than any of my credit or debit cards. Is this because it has its own power supply and doesn’t have to first be powered up by the machine?

NFC supports passive mode (where one side is powered and the card is not) and active mode (where both sides are powered). So, yes, your phone is probably more reliable because it provides a powered data transmission. An NFC card doesn't actively transmit data. Instead, it sends data using "load modulation", where it switches a load across the antenna to change how much power it absorbs. The transmitter can detect thi…

That’s insane. And yet when I see what we can do with coax or twisted pair, I anticipate we’ll get to gbps speeds one day. :)

Re: The tiny chip that powers Montreal subway tickets

#37

Post by lxgr »

amluto wrote: post #32

> Presumably, the makers thought that making the card look like a smart card would help people understand it. The card actually uses an entirely different technology. It’s kind of the same, though. The physical communication layer is different, but the higher protocol layers are basically identical. Smart cards with contacts follow ISO 7816. These MIFARE contactless cards are ISO 14443 Type A cards, and their protoco…

Only ISO 14443-4 uses the same protocol as ISO 7816 (another way of saying this is that ISO 14443-4 represents the higher layers of ISO 7816 over a different physical interface), though.

MIFARE Ultralight does not actually implement 14443-4/7816/"smartcard"-style APDUs; it's significantly simpler, since the ICs are much less powerful.

To make things more confusing, some MIFARE ICs really do implement ISO 14443-4 (e.g. their fixed-function MIFARE DESfire cards, and their programmable smartcard ICs like SmartMX), but not all of them.

Re: The tiny chip that powers Montreal subway tickets

#38

Post by ClumsyPilot »

bobthepanda wrote: post #3

This wasn’t super obvious to me until later in the article but this is about the single use tickets. Neat stuff, though I can’t say I love the concept of e-waste NFC.

Indeed, I didn’t know what kind of ticket we are talking about - folks please include a picture and some context in your blogs, for people from other places and countries

Re: The tiny chip that powers Montreal subway tickets

#40

Post by lxgr »

gruez wrote: post #31
bboygravity wrote: post #29

Earlier quoted context omitted.

The chip is the size of a grain of salt, but there's a relatively huge antenna inside made of conducting material (metal?) and glue and all that.

all of that is probably negligible compared to how much disposable foil is used for cooking or packaging.

On one hand it is probably small in comparison, but on the other hand, it seems much more feasible to reuse transit ticket ICs than e.g. food packaging.

Many transit agencies do explicitly incentivize reuse, e.g. by offering cheaper fares using a reloadable contactless card and often charging a deposit for that card.

Even then, many of these systems have been struggling due to the IC shortage, given the low margins these single-use tickets have to operate on. In some Asian countries, including Japan and Malaysia, it was tricky to get a new transit card for several months or even years, even though there is a deposit charge.

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