NFC antenna plugged in Seeed XIAO nRF52840

Hi folks,

Could anyone show me or explain me how can I plug in NFC antenna to seeed xiao nRF52840?

this is a 13.56 MHz antenna… wifi is 2.4Ghz… i dont think it is designed to work

Thanks for the quick response.
However in my case it is seeed xiao nRF52840 and I am talking about an NFC antenna.

apparently that device has a built in antenna

in any event, that antenna would only work as designed on a product which is capable of transmitting on the tuned frequency

you might try a XIAO ESP32 if you want to see if that antenna would work

you might be able to desoulder the antenna and connect directly… again i dont think the device is capable of transmitting on 13.5

I’m just following the documentation.

there you go… soulder the antenna to the pads

My intention was to find out if anyone had done this. Because I’m not sure how I can do this.

Hi there,
Check out the Nordic website docs for the Resistors R’s (x2) you need to match the (Z)impendence of the antenna, others have done it. Basically you measure the resistance of the antenna and match it with a value of resistor. Look at the Data sheet for the equation.
GL :slight_smile: PJ

The one you linked to in the first post, with caveats’ , C’mon man LOL…The other antennas will NOT work. :face_with_peeking_eye: FWIW you need to have an antenna compatible with the frequency and bandwidth for the spectrum you are operating in. Otherwise one could just use a coat-hanger :face_with_hand_over_mouth:

The NFC-Antenna-p-1805 has a U.FL connector, but seeed xiao nRF52840 hasn’t U.FL receptor.
Should I remove the connector and then solder? If I’m correct how can I do this?


yes… or you could unsoulder from the antenna side and connect wires there

Yes, as he said…or get these, and make a pigtail…
U.FL Connector 5 Pack — RaceDayQuads $5.
GL :slight_smile: PJ


yes what he said… lol

FYI, I’ve just soldered the peripherals.

However, it seems the mde card is not functional yet, I cannot read the NFC tag on my cell phone.


WOW thanks for the update!

Hi there,
Yea, That’s NEVER gonna work that way.!
Unfortunately it’s NOT a Plug and Pray connection, You :index_pointing_at_the_viewer: got MORE work to do , LOL
see this from the Nordic Sheet, and others have had success with:

NFC uses two pins, L24 (NFC1) and J24 (NFC2), to connect the antenna. These pins are shared with GPIOs (P0.09 and P0.10) and the PROTECT field in the NFCPINS register in UICR defines the usage of these pins and their protection level against abnormal voltages. The content of the NFCPINS register is reloaded at every reset.

Note: The NFC pins are enabled by default.
NFC can be disabled and GPIOs enabled by defining the CONFIG_NFCT_PINS_AS_GPIOS variable in the project settings. The way of doing this depends on the Integrated Development Environment (IDE)/toolchain in use:

When using SEGGER Embedded Studio, select Project > Edit Options > Code > Preprocessor > Preprocessor Definitions and add the CONFIG_NFCT_PINS_AS_GPIOS variable.
When using Keil, go to Project > Options for Target > C/C++ > Preprocessor Symbols > Define and add the CONFIG_NFCT_PINS_AS_GPIOS variable.
Pins L24 and J24 are by default configured to use the NFC antenna, but if they are needed as normal GPIOs, R44 and R46 must be NC and R43 and R45 must be shorted by 0R.

see Figure Two.

It would be wise to read the data-sheet and some of the other posts on how to implement it correctly.
GL :slight_smile: PJ

I have the Nordic , Dev board it comes with an NFC antenna, I’ll measure the Z and get back.
as a point of reference , what is the (r) of your antenna?

why would they make an antenna that needs extra stuff added to make it work… what da?

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Doesn’t make sense. The antenna should fix these extras.

Hi there,
IDunno, The LIB was broken a while back, But some others have posted they got it to work
No clear Solution on it yet other than Nordic’s Dev brd.
GL :slight_smile: PJ

@PJ_Glasso anyway, thank you for your time.

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No problem… :wink: :+1: