The tiny chip that powers Montreal subway tickets • Hacker News Board

Re: The tiny chip that powers Montreal subway tickets

#521

Post by hgomersall » Wed, Jun 26, 2024, 7:32 PM UTC

bunderbunder wrote: post #507

efreak wrote: post #500

Earlier quoted context omitted.

> Montreal is currently working on upgrading the system to allow people to just tap-to-pay at the turnstiles using their phones or compatible credit and debit cards. > Which is not something that you could do with a QR system I've got several apps that display QR codes on the screen for an external reader. One of them is for my health insurance id card (a simple 10 digit number), another shows my COVID vaccination st…

By tap-to-pay, I mean you need no special apps, you need no special accounts, any of that. You can pay with any physical credit or debit card that supports tap-to-pay, or you can use any credit or debit card you have loaded into your phone. With a QR code like that, people still need to install an app, set up an account, etc. It's just a lot more friction. In cities where I can tap-to-pay, getting set up to ride a bu…

Really? Setting up contactless payment is quicker than having a QR code image? I use QR codes on the UK train system and I don't have any special apps. It seems to integrate with Google wallet too, which surprised me.

Re: The tiny chip that powers Montreal subway tickets

#522

Post by CraigJPerry » Thu, Jun 27, 2024, 6:39 AM UTC

rswail wrote: post #514

CraigJPerry wrote: post #393

Earlier quoted context omitted.

>> there’s less need for centralization of data storage and code logic You make it sound like less moving parts are a bad thing :-) I know what you're getting at though - the decentralized tolerance of network partitions and the ability to provide higher availability and faster decision speed at the entry barrier. The system design constraints are hard but not impossible, my back of napkin maths says 5k/ticket scans…

The usual maximum time allowed for tap->barrier open is a maximum of 450ms. That includes all read/write times for the token, display changes, fare calculations and deductions, all business rule validation (eg hotlisting stolen tokens etc). The system I recently put in allowed for that 450ms, the time broke down to: 1) NFC comms ~100ms 2) Network comms ~50-100ms 3) Physical relays (releasing barriers etc) 100-200ms D…

“99th percentile”

Re: The tiny chip that powers Montreal subway tickets

#523

Post by rswail » Thu, Jun 27, 2024, 7:37 AM UTC

CraigJPerry wrote: post #522

rswail wrote: post #514

Earlier quoted context omitted.

The usual maximum time allowed for tap->barrier open is a maximum of 450ms. That includes all read/write times for the token, display changes, fare calculations and deductions, all business rule validation (eg hotlisting stolen tokens etc). The system I recently put in allowed for that 450ms, the time broke down to: 1) NFC comms ~100ms 2) Network comms ~50-100ms 3) Physical relays (releasing barriers etc) 100-200ms D…

“99th percentile”

Not relevant. The maximum specified by contract is usually 450-500ms.

The barriers at rail stations have to have a defined maximum throughput of passengers, because it affects safety during emergencies etc. Most barriers are required to maintain somewhere between 30 and 45 passengers per minute.

Yes they can "default be open" and usually have emergency modes that disable validation entirely, but the speed during peak hour periods has to maintain the passenger flow.

Re: The tiny chip that powers Montreal subway tickets

#524

Post by fennecfoxy » Fri, Jul 05, 2024, 3:44 PM UTC

BiteCode_dev wrote: post #401

fennecfoxy wrote: post #362

Earlier quoted context omitted.

Touch x against y versus line this weird printed shape up at just the right angle in good lighting conditions. I feel like NFC is much easier to tell older folks how to use as well. I'm all for the "we have technology why tf don't we use it, why aren't we better at it" argument, but the truth is that a lot of tech/systems in transport & other areas are retro af and new stuff gets shoe-horned in with all the caveats o…

> weird printed shape up at just the right angle in good lighting conditions None of that matter. QR code can be read on any angle because of the 3 position detection patterns it comes with, by design. Lighting conditions are not a problem on tickets (which is what the article is about) because you can illuminate the paper from the camera. QRCode were fast on assembly lines two decades ago. They were invented in the…

You speak about reader sourced illumination but there's a reason that phone screens go to full brightness when trying to scan a digital barcode.

Re: The tiny chip that powers Montreal subway tickets

#525

Post by fennecfoxy » Fri, Jul 05, 2024, 3:49 PM UTC

cypherpunks01 wrote: post #63

My favorite household NFC usage? NFC alarm clock. Makes me get out of bed and tap my phone on a specific NFC tag placed somewhere around the house, in order to turn off the alarm. Then, I may as well wake up, since I'm already out of bed : ) It's a nice companion to help perform 'habit stacking' as Atomic Habits calls it. Want to do pushups right after waking up? Place an NFC card under your workout mat, so you're fo…

I use "alarm clock xtreme" on Android that is similar; it has math and "type these random characters" puzzle as well as snooze detection so you hit "I'm awake" but also includes snoozing/stopping via number of steps detected or by scanning a barcode etc. Definitely recommend it.

But even so, I wish it would force me to key in the current time to disable, that way my sleepy brain would better understand "it's time to wake up now, because it is x time".