[System Power off]

[annapalu]

Hi all, i use the function sd_power_system_off() to put the micro in system off. First question is about the the type of system off. There are different type of system OFF:

IOFF_RAMOFF_RESET System OFF,  No RAM retention,   Wake on reset     0.7 μA
IOFF_RAMOFF_GPIO System OFF,   No RAM retention,   Wake on GPIO      1.2 μA
IOFF_RAMOFF_LPCOMP System OFF, No RAM retention,   Wake on LPCOMP    1.9 μA
IOFF_RAMOFF_NFC System OFF,    No RAM retention,   Wake on NFC field 0.7 μA
IOFF_RAMON_RESET System OFF,   Full RAM retention, Wake on reset     1.0 μA

How can i understand what power off type i'm using? Second question i see a consumption of 0.5 uA, but sometimes it increase to 1.5/ 2 uA, someone have any idea about the reason?

Thanks, anna

[Jørgen Holmefjord]

Hi,

The current consumption in system off mode is determined by the configured RAM retention and wakup sources. If you have not configured any wakeup sources, you the only way to wake from system off is by triggering a reset. The wakeup sources and reset behavior is described in the product specification of nRF52832 in the infocenter.

Is there anything special going on when the current increase, or is your device in any special states? Have a look at this thread about minimizing current consumption on nRF51 devices. Most of the methods also apply to nRF52 devices.

Best regards,

Jørgen

[annapalu]

Hi, thanks for the answer. I set the Gpio button to wake up the device, and it works correctly, when i press button the device wake up and there is a reset of my board. As long as i press the button, i aspect that the system stay in power off mode. I'm sure that there isn't a wakeup from system off, but seems that there is something that runs that cause the increase of consumption, when the system stays in system off.

About the RAM retention when i can find the type to set it, is there an example?

[Jørgen Holmefjord]

When put in System off mode, only the peripherals configured to wake the devices is enabled. The current consumption cannot change when in system off mode. Any wakeup from system off will cause a reset, making the code run from the start again. These nRF5x PowerDown examples on our GitHub shows how to configure RAM retention and setting up wakeup sources for system on and system off mode. There is also a RAM retention example in the SDK.

[annapalu]

I'm sure that the problem is not the reset of device, because i have a led that put on at the beginning of the code, and i put off before to go in power off mode. For example if i debbugger , i see a led to turn on and off. Without debbugger the led put on only at the first time and stay off.

[Jørgen Holmefjord]

What are you using to measure the current consumption? The increased current you see can be the refresh spikes, as described in this post.