Why use WFE instead of sd_app_evt_wait() on SDK15/FreeRTOS?

[loquat]

I try to use SDK15/FreeRTOS project.

I measured current comsumption on IDLE state(not run any task).

It's take about 200uA.

On FreeRTOS's portable/CMSIS/nrf52/port_cmsis_systick.c line239

#if 0  // With FreeRTOS sd_app_evt_wait increases power consumption with FreeRTOS compared to _WFE (NRFFOSDK-11174)

I try to change "#if 1", current comsumption is reduced.

Why disable sd_app_evt_wait()?

[Susheel Nuguru]

Hi,

We tested on PCA10040 and PCA10056 and in my tests i saw a clear increase in power when using sd_app_evt_wait() and less power with _WFE. That was the reason it was disabled and i created a new internal issue NRFFOSDK-11174 to investigate this. Can I know your test setup? which hardware are you testing this on?

[loquat]

I test on BLE NANO2(nrf52832 with DCDC).

I measured  current comsumption both. (attached files)

Description:

On center, PowerOn.

[Susheel Nuguru]

I have not tested this with DCDC, only tested with default LDO. 

But if your tests shows that sd_app_evt_wait shows better results then it is really good news. Please remove the #if 0 condition to make it work normally for you.

I have to do more tests when I have some time using DCDC and LDO on both nRF52832 and nRF52840 to get a proper idea.

 

[loquat]

OK

Thank you.

[miaojb12]

Hi,

I tested on PCA10040,it's take about 6.9mA when using sd_app_evt_wait() . Other hand, it's take about 0.92mA when using  _WFE.

Do you know how to cut down the left 0.92mA to 0.01mA?

I tested the demo project  ble_app_hrs_freertos.