NFC Callback Event Payload Details

[Mark J]

Hi,

We are evaluating use of the NFC functions on our nRF52840 - based solution (currently we use BLE). I have been able to understand how NFC Tag payloads are setup within the SDK and how these payloads are delivered. Docs and examples seem to be quite clear on this. I am, however, struggling to understand what data is coming in whenever a Tag scan occurs. I see the various event types that are set within the callback (nfc_t4t_callback_t and nfc_t2t_callback_t), but I see no detail on the payload provided with each type. 

We would like to understand if there is any distinguishing Id for the reading/scanning device that can be read so that we can setup an NDEF payload based on the reader/scanner Id. Ideally - this info is available for the NFC_T2T_EVENT_FIELD_ON orNFC_T4T_EVENT_FIELD_ON events.

Note that our firmware is indifferent and can support either Type 2 or 4 tag emulation..

If I am simply not finding the Nordic docs on this - apologies in advance.

Regards,

Mark J

[Jørgen Holmefjord]

Hi,

There is some information in nfc_t4t_event_t and nfc_t2t_event_t about the events and available parameters. 

We would like to understand if there is any distinguishing Id for the reading/scanning device that can be read so that we can setup an NDEF payload based on the reader/scanner Id. Ideally - this info is available for the NFC_T2T_EVENT_FIELD_ON orNFC_T4T_EVENT_FIELD_ON events.

I cannot find any information about any point that the NFC reader/initiator will send its own ID to the tag during the selection procedure. If this is received at all, I think that it will only be available inside the closed-source NDEF library, and not to the application. The FIELD_ON events are generated when the tag detects a field. This happens before any data is exchanged, so there are certainly no ID available at this stage. I think that the initiator must write its own ID implicitly to the tag if this should work as you want, but I can check with the developers tomorrow if they have any other suggestions.

You can find some information about the NFC-A commands here, and the command flow here.

Best regards,
Jørgen

[Mark J]

Hi Jørgen Holmefjord,

Thanks for the reply. The Android dev links may provide some good info. I will start by logging the payload for NFC events (NFC_T2T_EVENT_DATA_READ and NFC_T2T_EVENT_STOPPED) using the Nordic example (nfc_url_record) and look for distinguishing and repeatable payload components when swapping reader devices (ie Smartphones). I will use my nrf52 DK for this. This might be the fastest option to determining if there is something that we can (possibly) use. If the payload contents look promising, I can dig further into protocol details. 

Thanks,

Mark J