NFC Stops Working

[ketek]

Hi

We are doing field trials of a nRF52840 product with s140 SD, now and again NFC stops working (tag type-4, read and write).

This has been seen in SDK15.3.0 with SD6.1.1 and SDK16.0.0 with SD7.0.1.

Basically NFC stops responding, all NFC callbacks stop but nothing else is affected, when the nRF52840 wakes from sleep or is reset NFC works fine again.

It doesn't seem to be repeatable although I have seen the issue three times, once when debugging, other users a lot more - we use or own PCB NFC antenna, can this be causing too high a voltage at resonance? Or is it the NFC engine itself?

The data sheet states that NFC current must be limited to 80mA and the nRF52840 shorts the NFC pins when greater than 2V. Can the NFC pins be AC coupled or will this mess up any DC biasing? Can series resistance be added?

Thanks

Ken...

[Simonr]

Hi Ken

This does not seem like a hardware related issue to me. Are you able to provide any debug logs from when this occurs so I can take a look at it? 

Best regards,

Simon

[Otso Jousimaa]

Just letting everyone know that I've seen same issue on 52832 with SDK12.3, 15.3, 17.2. This is potentially related: https://devzone.nordicsemi.com/f/nordic-q-a/50681/nfc-tag-stops-working-suddenly-in-very-rare-cases .

I've not been able to get a debug log, this is something that happens once per week of NFC developing. Whatever is the root cause seems to bring the nRF52 out of the sleep, so this also leads to a fast battery drain at least in my case

[Simonr]

Hi

Thank you for the update. If you'd like help getting to the bottom of this, please create a new ticket where you describe your issue in detail and possibly link to these two cases, and we'll do our best to assist you.

Best regards,

Simon