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NFC reader detection field?

Hello:

I've got a application where I want to detect if the NRF52 is near a NFC reader. I don't need two way communications, but it would be good if the reader could modulate the 13.56 mhz signal (and I can do this custom in hardware if need be).  Using just a oscilloscope and a raw NFC 13.56mhz antenna I can detect energy out to about 10 inches with just a stock reader or Android phone. 

Can the NFC hardware/software be set to detect a NFC field? 

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  • Yes indeed Jeff, nRF52 NFC front-end can detect the field and you can get event FIELDDETECTED event callback. You can also wake up the device by 13.56MHz field from SYSTEM_OFF mode (see SDK "./examples/nfc/wake_on_nfc/").

  • Thank you, that gave me enough direction to dig into it further. But I had some followup questions.

    Under the hardware spec, the field detect needed 1 volt peak to peak signal to trigger. I didn't see where it was settable in firmware. I'm able to get good decodes on the scope in the 10mv  (0.01 VPP) level.   I realize the assumption of 1 VPP is with the back-channel (loading) modulation which I don't need.

    To expand on what I am trying to do, I want a NRF52 tag to recognize when it is near a NFC reader, which will be configured as a beacon... thing of active RFID vs. passive. So my "reader" will be custom, and won't be a reader, just sending out a modulated 13.56mhz signal that the NRF52 needs to decode via the NFC pins in/antenna.

    So the specific followup questions would be:

    Can I get the decoder to trigger/work below 1Vpp?  (if not I imagine I can add a amp ahead of things)

    Can I decode one way data? 

    I realize this is out of spec for the part, but using NFC would allow me to use the NFC module as a choke point decoder for finer accuracy in location applications. 

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  • Thank you, that gave me enough direction to dig into it further. But I had some followup questions.

    Under the hardware spec, the field detect needed 1 volt peak to peak signal to trigger. I didn't see where it was settable in firmware. I'm able to get good decodes on the scope in the 10mv  (0.01 VPP) level.   I realize the assumption of 1 VPP is with the back-channel (loading) modulation which I don't need.

    To expand on what I am trying to do, I want a NRF52 tag to recognize when it is near a NFC reader, which will be configured as a beacon... thing of active RFID vs. passive. So my "reader" will be custom, and won't be a reader, just sending out a modulated 13.56mhz signal that the NRF52 needs to decode via the NFC pins in/antenna.

    So the specific followup questions would be:

    Can I get the decoder to trigger/work below 1Vpp?  (if not I imagine I can add a amp ahead of things)

    Can I decode one way data? 

    I realize this is out of spec for the part, but using NFC would allow me to use the NFC module as a choke point decoder for finer accuracy in location applications. 

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