"floor" current of 2.9 mA with code migrated to SDK15 (from SDK12)

RE: "floor" current of 2.9 mA with code migrated to SDK15 (from SDK12)

ThierryC — Wed, 08 May 2019 13:26:01 GMT

OK, I found the problem: I was correctly using the nrf_power_mgmt_run(), but I forgot to define NRF_PWR_MGMT_CONFIG_FPU_SUPPORT_ENABLED !

So problem is solved ! Thanks for your hints.

And for the story, what I still don't understand, is why I didn't saw this problem on SDK12 using sd_app_evt_wait() ? If someone has an explanation.

RE: "floor" current of 2.9 mA with code migrated to SDK15 (from SDK12)

ThierryC — Wed, 08 May 2019 11:40:57 GMT

Hmm, investigating more deeply, it seems more to be around RTC.
I found this link and it seems to be exactly the use case I encounter (3 mA consumption after I get access to RTC->COUNTER) : https://devzone.nordicsemi.com/f/nordic-q-a/40102/app_timer_cnt_get-causing-high-power-consumption/156812#156812
So I try now the suggested fix... but difficult to setup on my Crossworks environment.Let see if it solve the issue after...

RE: "floor" current of 2.9 mA with code migrated to SDK15 (from SDK12)

Kenneth — Wed, 08 May 2019 08:25:17 GMT

If it is related to logging, then you can see how the SDK have solved this by waiting for logging to finish before going to sleep:

if (NRF_LOG_PROCESS() == false)
{
    nrf_pwr_mgmt_run();
}

The UART is the usual suspect when it comes to elevate current consumption during sleep, however it may also be other peripherals that are keeping the system powered, so I am not sure if I have any good suggestion than to for instance try to test a bit more.

RE: "floor" current of 2.9 mA with code migrated to SDK15 (from SDK12)

ThierryC — Tue, 07 May 2019 13:30:54 GMT

Here's more hints after further investigation :

If I put nrf_pwr_mgmt_run() call in a loop at the begin of my main (after SD and BLE stack init), I got correct power consumption (almost zero or few uA)
If I move this loop later on may main init sequence, I got ~3 mA power consumption
Experimentally, I found the limit for 0 to 3 mA consumption to put the loop, and this is just after ONE (not the first) line sending some debug log to SERIAL.
If I put a LOG line into the nrf_pwr_mgmt_run() LOOP, event at the beginning of the main, the log is LOGGING forever... but maybe this is intended.
So I conclude this is due to logging into SERIAL, but in RELEASE build, I have same issue (but later on the main init sequence, seems to be at random line).

Reading your link, is seems to be something like point 1. in Software section : race condition and pending interrupt. But how to figure out the root cause of that ? Could it be related to interrupts priorities ? Any hint for this subject ?

RE: "floor" current of 2.9 mA with code migrated to SDK15 (from SDK12)

ThierryC — Tue, 07 May 2019 09:51:09 GMT

Thanks for the link.
On my case, I'm not using the nrf_power_mgmt module. I'm calling directly sd_app_evt_wait(). Which is working fine of SDK12, but maybe I missed something.
I'll investigate more in this direction.

RE: "floor" current of 2.9 mA with code migrated to SDK15 (from SDK12)

Kenneth — Tue, 07 May 2019 08:27:27 GMT

In general you may check out:
https://devzone.nordicsemi.com/b/blog/posts/optimizing-power-on-nrf52-designs

You may also take a look at the nrf_pwr_mgmt_run() implementation from the nRF SDK.