problem with NFC handling

RE: problem with NFC handling

Vidar Berg — Mon, 26 May 2025 13:49:49 GMT

Thanks for confirming that we are talking about wakeup from System OFF mode. The WDT configuration and counter value are retained through this reset, so the question still remains if there is a possibility that device can wake up with a timeout that is too short.

Ref. Reset behaviour

RE: problem with NFC handling

HadarMiz — Mon, 26 May 2025 13:06:14 GMT

system off

RE: problem with NFC handling

Vidar Berg — Mon, 26 May 2025 12:52:53 GMT

Again, what does ULP (Ultra Low Power) refer to in this context? Is the device woken up from System OFF or System ON mode?

RE: problem with NFC handling

HadarMiz — Mon, 26 May 2025 12:44:39 GMT

I don't believe this issue is related to ULP. The device wakes up and begins receiving interrupts from the NFC as expected.

However, it's possible that a fault in the NFC-related interrupt handling could cause the device to become unresponsive.

RE: problem with NFC handling

Vidar Berg — Mon, 26 May 2025 12:39:28 GMT

Is ULP = System OFF mode? In that case, does your code reload the watchdog just before entering System OFF mode to ensure the timeout is consistent upon wakeup?

RE: problem with NFC handling

HadarMiz — Mon, 26 May 2025 12:34:25 GMT

Hi Vidar,

We’ve observed a watchdog reset (WD) occurring when the device lands on the NFC pad. Here's the sequence:

The NFC wakes the device from ULP.
The NFC pad sends interrupts to the device.
In rare cases (approximately 1 in 10,000 devices), a watchdog reset occurs.

Our suspicion is that we may not be handling the NFC interrupts properly, which could occasionally cause the device to get stuck.

Regarding your other question, yes we're using your driver implementation.

Thanks,

RE: problem with NFC handling

Vidar Berg — Mon, 26 May 2025 12:27:28 GMT

Hi,

Not sure when or where the WD is fed in your case, but maybe the repeated NFC interrupts prevent the WD from being reloaded in time. Is the NFC field waking the device from System OFF or System ON mode, and are you using our NFC drivers or have you implemented your own? Please share relevant code snippets if possible.

Best regards,

Vidar