Low Power with SPI peripheral Zephyr

[Arturo Hache]

I'm trying to achieve a low power operation on a device which has a nRF52833 module with a SPI peripheral on Zephyr. It is based on the peripheral_lbs.

The intended behaviour is for the device to be connectable but low power while not used and active on connection, to perform the callback actions.

So far I've done the following on the prj.conf:

CONFIG_NCS_SAMPLES_DEFAULTS=y

CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y
CONFIG_BT_DEVICE_NAME="Foo"

CONFIG_PM_DEVICE=y

# Peripherals
CONFIG_SERIAL=n
CONFIG_SPI=y
CONFIG_NRFX_SPIM=y
CONFIG_NRFX_SPIM1=y
CONFIG_MAIN_STACK_SIZE=4096

# Enable the LBS service

CONFIG_BT_LBS_POLL_BUTTON=y

I'm aiming for the PM module to turn off SPI while the device is asleep, which I suppose makes most of the power consumption(130uA assuming the SPI device complies with the datasheet spec)

When I declare the SPI_Uninit function on my library for the SPI device:

void LED_spiDeinit(void)
{
        LED_GPIO_Deinit();
        spim_nrfx_pm_control(&spi_dev,PM_DEVICE_STATE_SET,spi_pm_cb,NULL);
}

I get the following build error, some lines are added for reference:

Archiving ‘libdrivers__gpio.a’
Building ‘zephyr/drivers/spi/libdrivers__spi.a’ from solution ‘build’ in configuration ‘Common’
Compiling ‘spi_nrfx_spim.c’
Archiving ‘libdrivers__spi.a’


Building ‘zephyr/zephyr_prebuilt.elf’ from solution ‘build’ in configuration ‘Common’
Linking ‘zephyr_prebuilt.elf’
app/libapp.a(PCA9957.c.obj): in function `LED_spiDeinit':
undefined reference to `spim_nrfx_pm_control'
ld returned 1 exit status
Build failed

How can I solve this?

[Susheel Nuguru]

I do not think you should call the power management callbacks directly from the applications, that is the reasons callbacksk to the PM policies like spim_nrfx_pm_control are static in nature so that they are not visible to your application.

If you still want to do this via power management module, the best way is make sure that CONFIG_SYS_POWER_MANAGEMENT is enabled and use pm_device_state_set so that power the callback you are intending to call can be triggered through power management module.