Achieving lowest possible sleep current on nRF52840

RE: Achieving lowest possible sleep current on nRF52840

robca — Tue, 18 Jun 2024 16:55:56 GMT

This is exactly what I needed, thanks. I'll do a couple of tests to ensure I can hit the expected power, on sleep, then close this issue

Thanks again for the help

EDIT: yes, everything works as expected after manually disabling every peripherals and setting all used pins as GPIO default

RE: Achieving lowest possible sleep current on nRF52840

Simonr — Tue, 18 Jun 2024 13:28:58 GMT

In system OFF mode, RAM retention will be off by default, and you only need to enable it if needed. We have an example project for RAM retention in the nRF5 SDK available here: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/ram_retention_example.html

The clocks will be handled "automagically", so if no peripherals are polling the HF clock for instance, it will be turned off and thus no longer running. system OFF will also turn off these clocks.

Best regards,

Simon

RE: Achieving lowest possible sleep current on nRF52840

robca — Mon, 17 Jun 2024 18:19:30 GMT

That's what I thought, thanks for you answer. I'll check how to programmatically determine if a peripheral is initialized.

Can you please help me figure out how to turn off RAM retention for all blocks using the nRF5 SDK? I must be reading the documentation wrong, as what I tried seems to make no difference.

Lastly, should I turn off any of the clocks before calling sd_power_system_off?

RE: Achieving lowest possible sleep current on nRF52840

Simonr — Mon, 17 Jun 2024 11:35:23 GMT

sd_power_system_off does not uninitialize the so if I.E. the QSPI isn't uninitialized it might be that the external flash for example is left running, which could be what you're seeing here. I would recommend checking if any of the pins from the nRF52 is drawing this excess current with a multimeter or scope as a first step. Only by reading the registers you can see what the different peripherals are set to. I would recommend that you do uninit the peripherals used before or as part of your "going to sleep" function.

Best regards,

Simon