- SDK15.3
- SES
- nRF52840
Hello Folks,
I'm trying to reduce my applications power consumption further in system off mode. For testing my IO configuration and System OFF, I've reduced the application to just the GPIO initialization and going to System OFF with a call to nrf_pwr_mgmt_shutdown as I don't even have the soft device enabled.
My test code is as following:
int main(void)
{
uint32_t ret;
GpioInit();
#if NRF_LOG_USES_TIMESTAMP
ret = NRF_LOG_INIT(get_timestamp_counter);
#else
ret = NRF_LOG_INIT(NULL);
#endif
APP_ERROR_CHECK(ret);
NRF_LOG_DEFAULT_BACKENDS_INIT();
while (1)
{
nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF);
}
}
With this piece of code I have a power consumption of 1.766uA when measured with an Power Profiler Kit.
This comes close to the specified current consumption in the product Specification of having all RAM retained during System Off.
IOFF_RAMON_RESET System OFF, full 256 kB RAM retention, wake on reset 1.86 μA
As I don't need RAM retention due to the reset of the wake-up from System Off. I'd like to disable RAM retention. I couldn't find any specification whether the nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF) or sd_power_system_off() disable all RAM retention dusring System Off, but from my current measurement it looks like they don't. So according to the following examples; https://github.com/NordicPlayground/nrf51-powerdown-examples and the RAM retention example in the SDK, I've come up with the following:
#define NRF52_ONRAM1_OFFRAM0 ((POWER_RAM_POWER_S0POWER_On << POWER_RAM_POWER_S0POWER_Pos) |\
(POWER_RAM_POWER_S1POWER_On << POWER_RAM_POWER_S1POWER_Pos) |\
(POWER_RAM_POWER_S2POWER_On << POWER_RAM_POWER_S2POWER_Pos) |\
(POWER_RAM_POWER_S3POWER_On << POWER_RAM_POWER_S3POWER_Pos) |\
(POWER_RAM_POWER_S4POWER_On << POWER_RAM_POWER_S4POWER_Pos) |\
(POWER_RAM_POWER_S5POWER_On << POWER_RAM_POWER_S5POWER_Pos) |\
(POWER_RAM_POWER_S6POWER_On << POWER_RAM_POWER_S6POWER_Pos) |\
(POWER_RAM_POWER_S7POWER_On << POWER_RAM_POWER_S7POWER_Pos) |\
(POWER_RAM_POWER_S8POWER_On << POWER_RAM_POWER_S8POWER_Pos) |\
(POWER_RAM_POWER_S9POWER_On << POWER_RAM_POWER_S9POWER_Pos) |\
(POWER_RAM_POWER_S10POWER_On << POWER_RAM_POWER_S10POWER_Pos) |\
(POWER_RAM_POWER_S11POWER_On << POWER_RAM_POWER_S11POWER_Pos) |\
(POWER_RAM_POWER_S12POWER_On << POWER_RAM_POWER_S12POWER_Pos) |\
(POWER_RAM_POWER_S13POWER_On << POWER_RAM_POWER_S13POWER_Pos) |\
(POWER_RAM_POWER_S14POWER_On << POWER_RAM_POWER_S14POWER_Pos) |\
(POWER_RAM_POWER_S15POWER_On << POWER_RAM_POWER_S15POWER_Pos) |\
(POWER_RAM_POWER_S0RETENTION_Off << POWER_RAM_POWER_S0RETENTION_Pos) |\
(POWER_RAM_POWER_S1RETENTION_Off << POWER_RAM_POWER_S1RETENTION_Pos) |\
(POWER_RAM_POWER_S2RETENTION_Off << POWER_RAM_POWER_S2RETENTION_Pos) |\
(POWER_RAM_POWER_S3RETENTION_Off << POWER_RAM_POWER_S3RETENTION_Pos) |\
(POWER_RAM_POWER_S4RETENTION_Off << POWER_RAM_POWER_S4RETENTION_Pos) |\
(POWER_RAM_POWER_S5RETENTION_Off << POWER_RAM_POWER_S5RETENTION_Pos) |\
(POWER_RAM_POWER_S6RETENTION_Off << POWER_RAM_POWER_S6RETENTION_Pos) |\
(POWER_RAM_POWER_S7RETENTION_Off << POWER_RAM_POWER_S7RETENTION_Pos) |\
(POWER_RAM_POWER_S8RETENTION_Off << POWER_RAM_POWER_S8RETENTION_Pos) |\
(POWER_RAM_POWER_S9RETENTION_Off << POWER_RAM_POWER_S9RETENTION_Pos) |\
(POWER_RAM_POWER_S10RETENTION_Off << POWER_RAM_POWER_S10RETENTION_Pos) |\
(POWER_RAM_POWER_S11RETENTION_Off << POWER_RAM_POWER_S11RETENTION_Pos) |\
(POWER_RAM_POWER_S12RETENTION_Off << POWER_RAM_POWER_S12RETENTION_Pos) |\
(POWER_RAM_POWER_S13RETENTION_Off << POWER_RAM_POWER_S13RETENTION_Pos) |\
(POWER_RAM_POWER_S14RETENTION_Off << POWER_RAM_POWER_S14RETENTION_Pos) |\
(POWER_RAM_POWER_S15RETENTION_Off << POWER_RAM_POWER_S15RETENTION_Pos))
int main(void)
{
uint32_t ret;
GpioInit();
#if NRF_LOG_USES_TIMESTAMP
ret = NRF_LOG_INIT(get_timestamp_counter);
#else
ret = NRF_LOG_INIT(NULL);
#endif
APP_ERROR_CHECK(ret);
NRF_LOG_DEFAULT_BACKENDS_INIT();
while (1)
{
NRF_POWER->RAM[0].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[1].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[2].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[3].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[4].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[5].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[6].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[7].POWERSET = NRF52_ONRAM1_OFFRAM0;
NRF_POWER->RAM[8].POWERSET = NRF52_ONRAM1_OFFRAM0;
nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF);
}
}
With the additional powerset register changes the power consumption is reduced to 1.383uA. However i have the following questions:
- My application needs to wake-up from two gpio events; a reed-switch and a tilt sensor. Is it possible to reduce the power consumption further? I think I've correctly disabled the RAM retention for System Off. But I doubt that without the hardware on my board the nRF52840 is actually drawing 0.4uA as specified in the product specification.
- On wake-up do I need to set the POWERSET registers back to default or are there contents not retained during the reset?
