Power consumption nRF9151

[LeonL]

When loading empty software (zephyr based) into the nRF9151, the nRF9151 uses roughly 4mA and when erasing the IC, it uses 5.8mA. 

Does zephyr not include a power down mode when running 'empty software'? What could be the cause of this relatively high power consumption when doing nothing?

[Kenneth]

Hello,

The chip does not enter any kind of power down or idle mode unless there is specific project compiled for the chip in question that actually do this. So for instance when chip is recovered or erased the chip will just start executing code from beginning of flash and try to execute whatever is there. An empty flash is normally all '1's, or 0xFFFFFFFF in hexadecimal value. If the cpu tries to execute 0xFFFFFFFF, it will likely result in a UsageFault or HardFault, as it does not correspond to any valid opcode. This again may cause a CPU lockup and and a reset. So likely there is an infinite loop of resets.

Kenneth

[LeonL]

Hello Kenneth, 

Thanks for the response.

This clears up the high power consumption when erasing the IC.

If however you flash the IC with an empty sketch based on the zephr environment, I'd expect that zephyr would force the IC into an idle / sleep mode as there are no tasks defined and the flash is not empty?

With empty sketch I mean an empty main():

#include <zephyr/kernel.h>

int main(void) {

    while (true) {
        k_sleep(K_SECONDS(10));
    }
}

[Kenneth]

But is this the project that is actually programmed? Also have in mind that if for instance logging and serial is enabled, it will never actually enter idle, ref:
https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/test_and_optimize/optimizing/power_general.html#disable_serial_logging 

Also check out in general:
https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/test_and_optimize/optimizing/power.html 

The best as mentioned is to start with an example project that was intended for the nRF91 to start with, with proper devicetree overlay files if needed etc.

Kenneth

[Mark Szente]

I'm also seeing similar results to that of the OP. When I run the above code (or the Blinky sample, for example) as-is, I'm seeing around 3.7mA average consumption. If I disable serial as per optimization guide, it drops to 3.17mA on average. I still see the spikes every 10 (or 1, in Blinky) seconds when the CPU starts executing instructions.

What am I missing? Using brand new nRF9151-DK and PPK2. 

[Achim Kraus]

Blinky on the nRF9151 just doesn't send the modem to sleep.

Try

#include <modem/lte_lc.h>

#include <modem/nrf_modem_lib.h>

int main(void)

{

nrf_modem_lib_init();

lte_lc_power_off();

k_sleep(K_MSEC(1000));

NRF_REGULATORS->SYSTEMOFF = 1;

return 0;

}

(Not sure, if that compiles. Usually the UDP sample is a good point to check the prj.conf).

Anyway:

@Nordic

After sooo many tickets about the quiescent current, I would enjoy to have "maintained samples" for each board demonstrating that, along with numbers to expect for each board.