Fix for ACR122U Time Extension

Hi all,

I’ve been doing a fair bit of work with smartcard readers for a long time, and I’ve butted heads with the ACR122U reader multiple times. It just doesn’t support key generation - the reader decides the chip has taken too long (and doesn’t listen to time extension requests) and resets - this is a major issue in development of apps (I ended up buying a Feitian R502-CL in frustration). I’ve actually discovered a solution to this and I’m posting in the hopes others will be able to avoid my frustrations (these are the cheapest CCID compatible contactless reader around). if you send APDU 0xFF0041FF00h via GlobalPlatformPro (or your preferred APDU send method) with a chip on the reader, the reader will intercept this command and set the timeout to wait for a smartcard to reply. I’ve tested this and it’s not persistent across unplugs of the reader, but it will survive a card reset.


I like your topic. It’s very useful for me

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Thanks for that! That’ll spare me a lot of headaches when I start coding stuff from the NTAG413 in a few days/weeks.

How would you compare the Feitian R502-CL with the ACR122U in terms of read range (or maybe I should say, in terms of ease of detection/reading) with implants? I’m tempted to order one based on your feedback.

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Read range is similar, the Feitian is just far, far more reliable for APDU-based comms (usually only an issue on smartcards though). Basically, if you’re doing a long-running crypto or initialisation operation on a ACR122U, it can interpret it as a card reset if it goes over 2 or 3 seconds without this fix.

Unfortunately I lost my Feitian for the time being :expressionless:

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Okay. Well at EUR 31, I’ll order a couple. Even if it sucks, it won’t kill me. Thanks!

I have two, I’ll send you one in the next care package. Both of them for some reason have issues on my computer though… it’ll be interesting to see if the one I send also has problems on yours.

So which feitian reader are people using?

Would this work ?

That’s the one.

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thanks @fraggersparks - it should arrive in the mail shortly.

Well, I got my two Feitian R502-CL in the mail today, and they’ll be going straight into my collection of readers that I’ll never use. Their performances are really kind of shit. They read my implants, but barely.

They do make pretty good contact card readers though :slight_smile:

EDIT: nevermind, it seems the retailer sent me R502 readers (not -CL). I’ll be returning those I guess…

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