What could the nRF52840 be doing while apparently idle — and what are the risks of interrupting it with a reset?

RE: What could the nRF52840 be doing while apparently idle — and what are the risks of interrupting it with a reset?

Sigurd — Tue, 05 Aug 2025 11:48:50 GMT

[quote user="coiti4"]That said, my question is less about whether to reset and more about what the nRF52840 might be doing under the hood when it appears idle (no BLE connections, no advertising, no SPI activity).[/quote]

For most applications, if things are working correctly, then the CPU should then simply be sleeping, consuming the minimum amount of power.

[quote user="coiti4"]I’m trying to understand if things like deferred internal flash writes or SoftDevice tasks could still be happening silently and whether triggering a reset in that moment could corrupt data or cause other issues.[/quote]

That are things that the CPU could be doing, yes, but it should not cause any issues to trigger a reset in these cases. E.g. the FDS filesystem, and other systems are designed to be robust against sudden power failures. e.g. a battery-powered product could suddenly lose power when the battery is empty, and the systems are designed to be robust against that.

RE: What could the nRF52840 be doing while apparently idle — and what are the risks of interrupting it with a reset?

coiti4 — Tue, 29 Jul 2025 13:24:39 GMT

Thanks, I appreciate the perspective.

That said, my question is less about whether to reset and more about what the nRF52840 might be doing under the hood when it appears idle (no BLE connections, no advertising, no SPI activity).

I’m trying to understand if things like deferred internal flash writes or SoftDevice tasks could still be happening silently and whether triggering a reset in that moment could corrupt data or cause other issues.

Is there any guidance on how to tell when it’s truly safe to reset?

Best,
Agustín

RE: What could the nRF52840 be doing while apparently idle — and what are the risks of interrupting it with a reset?

Sigurd — Mon, 28 Jul 2025 13:22:13 GMT

Hi!

A reset is something done typically by fault/error handlers, and the Watchdog when it encounters a error. If you are using the Watchdog, and reset on faults in the FW, then I don't see the need for this kind of "preventive reset".