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

Hi,

I'm using the nRF52840 with the SoftDevice for BLE. In my system, it's primarily a BLE transceiver controlled via SPI by an external TI MSP430. We're considering implementing a preventive reset strategy: if the nRF appears idle (no BLE connection, no SPI activity) for a long time (e.g., 24 hour), we trigger a reset — either via an SPI interrupt (soft reset) or via a GPIO (hardware reset).

But I realize that “idle” from the outside might not mean truly idle internally.

So my question is:

What operations could the nRF52840 be performing while it appears idle externally?

  • Could it still be handling flash writes (e.g., bonding info, GATT attributes, flash queue, deferred writes)?

  • Could there be any background tasks from the SoftDevice?

And more specifically:

  • What is the worst-case outcome of interrupting such a state with a reset?

  • Are there ways to detect if it’s truly safe to reset, or to coordinate the reset in a safer way?

I'd appreciate any guidance for resetting this MCU safely under such conditions.

Thanks!

Agustín

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