LIS2MDL prevents nRF52833 from staying in SYSTEM OFF

[feathers]

I am using the common application framework of the nrf connect sdk. Specifically, I am testing the power manager module to put the board in OFF mode.

However, there is an issue whenever I include the node corresponding to the LIS2MDL magnetometer in my overlay file and I enable CONFIG_SENSOR and CONFIG_SPI.

Even if the board goes to sleep successfully, it will get awoken again within a second by what I can only assume is data coming in from the sensor which triggers a GPIO signal.

This behaviour simply does not happen when CONFIG_SENSOR is disabled, or when my overlay file does not include the LIS2MDL.

For reference, the board also has a LSM6DSO attached to the same SPI interface, which does not reset the board once in SYSTEM OFF.

Checking the LIS2MDL zephyr driver I noticed that it is supposed to handle suspension on its own, but clearly this is not happening.

Any help will be appreciated.

Kind regards,

feathers

[Jørgen Holmefjord]

Hi,

Which GPIOs are you using for connecting the sensor? I'm not sure if the power management library will reconfigure any GPIOs used by the sensor when you go to System OFF. If any GPIOs are configured as an input with SENSE enabled, the pin will wake the chip from System OFF if it detects an edge in the correct direction. Have you tried 

You can check if the wakeup from System OFF was caused by a GPIO or another source by reading out the NRF_POWER->RESETREAS register.

Best regards,
Jørgen

[Jørgen Holmefjord]

Can you try to manually disable the interrupt for the sensor interrupt pin before going to System OFF, to see if this is what is causing the wakeup?

gpio_pin_interrupt_configure_dt(&cfg->gpio_drdy, GPIO_INT_DISABLE);

[feathers]

I am not using the LIS2MDL trigger in my application, simply the SPI interface, therefore I am not sure which pin I would disable.
I also made a simple MRE that demonstrates this problem.
Simply by changing CONFIG_SENSOR from y to n the board stays in SYSTEM OFF successfully, otherwise it doesnt.
You can check it here.
github.com/.../SYSTEM_OFF_LIS2MDL_POC

Also worth mentioning I tried without the power manager to directly turn off power with

    nrf_power_system_off(NRF_POWER);

and it seems to work that way.


EDIT: I checked the register, and the reason is due to a soft reset (?) NRF_POWER_RESETREAS_SREQ_MASK.