Some event prevent the uC to enter low power mode

[Jose Xavier]

Hi,

After configure IO and RTC I tried to enter into low power mode however the current consumption doesn't decrease until I call again __SEV(); / __WFE(); / __WFE(); on CIO::buttonInterruptHandler per example.

In the code block below you can see the IO and RTC configuration. If instead of two __WFE() calls I do 4 calls the current consumption decrease to low power levels.

How can I find out which event is preventing nrf51822 to go into low power mode?

/* Configure inputs */
nrf_drv_gpiote_init();
nrf_drv_gpiote_in_config_t in_config;
in_config.is_watcher = false;
in_config.hi_accuracy = false;
in_config.pull = NRF_GPIO_PIN_PULLUP;
in_config.sense = NRF_GPIOTE_POLARITY_HITOLO;

/* Enable interrupt at button down */
nrf_drv_gpiote_in_init(BUTTON_DOWN, &in_config, CIO::buttonInterruptHandler);
nrf_drv_gpiote_in_event_enable(BUTTON_DOWN, true);

/* Enable interrupt at button up */
nrf_drv_gpiote_in_init(BUTTON_UP, &in_config, CIO::buttonInterruptHandler);
nrf_drv_gpiote_in_event_enable(BUTTON_UP, true);

/* Configure pin as output */
nrf_gpio_cfg_output(PIN_UPDOWN);
nrf_gpio_cfg_output(PIN_ENDISABLE);

nrf_drv_clock_init();
nrf_drv_clock_lfclk_request(NULL);

//Initialize RTC instance
nrf_drv_rtc_config_t config;// = NRF_DRV_RTC_DEFAULT_CONFIG;
config.interrupt_priority = RTC_DEFAULT_CONFIG_IRQ_PRIORITY;
config.reliable = RTC_DEFAULT_CONFIG_RELIABLE;
config.tick_latency = RTC_US_TO_TICKS(NRF_MAXIMUM_LATENCY_US, RTC_DEFAULT_CONFIG_FREQUENCY);
config.prescaler = 4095;
nrf_drv_rtc_init(&rtc, &config, rtc_handler);

//Power on RTC instance
nrf_drv_rtc_enable(&rtc);

__SEV();
__WFE();
__WFE();

[Stian Røed Hafskjold]

You must put the WFE call in the main loop

[Jose Xavier]

why?

If I put 4 WFE on the code above it works.

[Stian Røed Hafskjold]

Sorry I don't know what you are trying to accomplish, but normal programming practice is to put WFE in your main loop. Then the CPU will wake up to whatever event causing an interrupt, act upon it if there's a handler for the interrupt, and then go back to idle state. And repeat infinitely.

[Stian Røed Hafskjold]

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka15506.html

"Typically, sleep will take place when the processor loops around and re-executes the WFE instruction. The processor may wake up for spurious reasons from this spinlock sleep before the spinlock condition is eventually satisfied, but placing the WFE in the loop allows the processor to return to the sleeping condition repeatedly until the condition is met."

[Jose Xavier]

I want it to sleep on some specific states.