Minimizing power consumption

RE: Minimizing power consumption

Tim Adu — Thu, 14 Nov 2019 14:19:58 GMT

Thanks! It definitely helped. Managed to bring it down to 65uA in SYSTEM OFF. I had defined a dummy handler which was not returning true. I defined the shutdown sequence in my application but did not set the dummy handler to return true.

RE: Minimizing power consumption

Håkon Alseth — Wed, 06 Nov 2019 15:01:29 GMT

nrf_pwr_mgmt will execute a number of handlers before entering sleep, where that is defined on how many you have registered in your application via NRF_PWR_MGMT_HANDLER_REGISTER(my_pwr_mgmt_handler, PRIO), and if any of these returns false, it will not go to sleep.

If you do not have any handlers registered, then it'll go to systemoff directly.

Don't you have any pins to wake up on? Are you relying on NFC to wakeup?

Have you entered debug mode to see if the call to sd_power_system_off() in nrf_pwr_mgmt.c is called ?

RE: Minimizing power consumption

Tim Adu — Tue, 05 Nov 2019 15:18:51 GMT

As the very last step before calling the SHUTDOWN function

nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_GOTO_SYSOFF);

I reset all GPIO pins that are used by the application to their default states using nrf_gpio_cfg_default

Does it make sense to do this?

RE: Minimizing power consumption

Håkon Alseth — Tue, 05 Nov 2019 15:06:57 GMT

Good, then its not the nRF itself that is causing this, unless you are getting an assertion or similar.

When you enter SYSTEMOFF, all clocks are stopped, GPIOs are latched in their current configuration, and the nRF itself should not draw much power. Only way to wake up is on pin or reset.

However; if the GPIOs are latched as output, with either '1' or '0' towards an external device (LED, IC, or anything else), then that might draw current.

Could you check your GPIO configuration to ensure that there is nothing external that is misbehaving due to the latched GPIO settings?

Kind regards,

Håkon

RE: Minimizing power consumption

Tim Adu — Tue, 05 Nov 2019 14:43:52 GMT

I've tried that; the board is power cycled always before starting measurements.

Tim

RE: Minimizing power consumption

Håkon Alseth — Tue, 05 Nov 2019 14:37:28 GMT

Try power cycling the board, then measure with the PPK.

Cheers,

Håkon

RE: Minimizing power consumption

Tim Adu — Tue, 05 Nov 2019 14:22:39 GMT

Yes, it's static 4.5 mA.

I use Segger Embedded Studio to develop the application.

I have test setup that generates a production image, which contains the application (built using the Release config, not Debug), SoftDevice and Bootloader. After loading the image, then I start the PPK to do power consumption readings.

Tim

RE: Minimizing power consumption

Håkon Alseth — Tue, 05 Nov 2019 14:17:27 GMT

Hi,

Static 4.5 mA current consumption?

Are you by any chance in debug mode while checking this? Emulated system off, which will run in debug mode, will not give the expected result in terms of power consumption, and it is recommended that you add a while(1) loop after the call to system off in your firmware, for debugging purposes.

If you power cycle your device, it should go out of debug mode.

Kind regards,

Håkon