Would this NFC module fit in an Expansion Card?

Creators & Developers Expansion Card
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I’ve seen a few people asking about NFC readers for authentication in the expansion slot - but I don’t think any have been made.

The smallest reader I can find is the ACM1252U-Z2. According to the spec sheet, it is 20mm wide and 6mm tall. If the USB Micro female port cold be swapped to USB-C male, it should be able to fit in the expansion slot, right?

The only problem is the length. It’s 52mm. About half that is circuitry - the other half is the antenna. If it were bent 90deg in the middle, it would still be taller than the RJ45 expansion card.

There are things like this little one but that acts as a keyboard rather than a proper reader. So it won’t work with Yubikeys etc.

Has anyone found a smaller reader that could fit and do FIDO?

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Does anyone have a pointer to relevant documentation on how the reader should appear to the system? I assume it would be some form of HID device, which is probably what the one in your second link does to look like a keyboard.

What does a Yubikey look like to the system?

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To be clear, I’m talking about an NFC Yubikey - not a USB one.

An NFC reader looks like a PC/SC device.

I’ve a brief write up of a USB-C one at Review: An NFC reader/writer with USB-C – ACR1252U-MF – Terence Eden’s Blog

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I’d LOVE to get an NFC reader. If you can find one that has a separated antenna that is still small, you might be able to fold it over or be creative in wire/flex routing to manage to squeeze it in so the antenna would be towards the keyboard.
However, there’s still going to be some metal bits/etc likely in the way above the card, so that might still interfere. Not sure.

I found 13.56MHZ RFID Reader/Writer Module V4- Ultralight - ELECHOUSE which isn’t too far off. Almost narrow enough, but too long by ~9mm.

Also thinking about it, it operates over Serial UART, and would thus need a USB->Serial chip as well.

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Nope, if you change mils to mm, it’s 1950 mils → 49.53mm, 1605 mils → 40.767mm.

So sadly, nope, that’s for a single one. It’s still quite small and compact, but well oversized for an expansion card, sadly.

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I’ve found a couple of USB NFC readers which might fit into an Expansion Card.

Here’s my write-up Thoughts on building an NFC reader for the Framework laptop – Terence Eden’s Blog

The cards and soldering bits should be with me next week - so I’ll try them on my regular laptop as my Framework hasn’t shipped yet.

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any updates on your attempts? I want to build an NFC reader for my FW16 too! :grin:

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I’ve been looking into the NXP PN533. It’s a compact package (QFN50P600X600X85-40) with an integrated USB 2.0 interface.

The reference design for a compact USB stick should be a good starting point. The PCB carrying the chip, capacitors for supply voltage and the matching/filter circuit for the NFC antenna is small enough to fit into an expansion card.

While the NXP PR533/PN533 NFC reader chips are still marked as “active” on NXP’s website, they don’t seem to advertise for these anymore. Their more recent alternatives use SPI/UART/I2C for the host interface, where the expansion card would need an additional converter/interface chip.

The interesting part after deciding on a chip and PCB would be designing the sidewards facing NFC antenna with proper ferrite shielding. A downwards facing antenna would probably have a more appropriate cross section for an NFC reader/writer antenna but would also be less practical…

Both cases would probably need some engineering to find the proper matching circuit parameters for the antenna circuits as described in NXP’s antenna design guidelines. I wonder how feasible it is to determine these DIY without e.g. a vector network analyzer.