Simple wakeup on GPIO after sd_power_system_off

[Mishka]

Hi, I'm building a BLE peripheral with one button only. The button exposed over bluetooth. Obviously, the button handling module (GPIOTE) is used. After advertisement timeout the device goes off and then the button should be used to wake it up. Simple reset would be just fine. However, after entering sleep mode the device becomes unresponsive.

I'm prototyping on NRF52 DK, initialization code is as follows (please note it's compiled with CFLAGS+=-DBSP_SIMPLE):

#define CONTROL_BUTTON      BUTTON_1

static app_button_cfg_t buttons[] = {
    {CONTROL_BUTTON, BUTTONS_ACTIVE_STATE, BUTTON_PULL, button_evt_handler}
};

bsp_board_init(BSP_INIT_LEDS | BSP_INIT_BUTTONS);

err_code = app_button_init(buttons, ARRAY_SIZE(buttons), BUTTON_RELEASE_TIMEOUT);
APP_ERROR_CHECK(err_code);

err_code = app_button_enable();
APP_ERROR_CHECK(err_code);

Then the following code is executed on BLE_ADV_EVT_IDLE to put the system to sleep:

NRF_LOG_INFO("Power off");
NRF_LOG_FLUSH();
        
/* Prepare wakeup buttons */
nrf_gpio_pin_sense_t sense = BUTTONS_ACTIVE_STATE ?
      NRF_GPIO_PIN_SENSE_HIGH : NRF_GPIO_PIN_SENSE_LOW;
nrf_gpio_cfg_sense_set(CONTROL_BUTTON, sense);
        
/* Go to system-off mode (won't return; wakeup will cause a reset) */
err_code = sd_power_system_off();
/* NOT REACHED */
APP_ERROR_CHECK(err_code);

I see the "Power off" message, and the device stops responding to BLE and button press (no more calls to the button_evt_handler()). Everything after the sd_power_system_off() seem never executed. But the button can't wake the device up. It's either stuck somewhere in the sd_power_system_off() or I just misconfigured the wakeup button.

Looks like a trivial issue, but can't nail it down for the day :-/ Any help would be greatly appreciated.

[Mishka]

Today I've received my power profiler (cool thing guys). Looking to the chart it seems that the sd_power_system_off() doesn't do its job as intended (those tiny bumps right after advertising finished are from button press):

When I previously used BSP BLE button module the sd_power_system_off puts the device to sleep indeed.

[Einar Thorsrud]

Hi,

I do not see anything wrong in your code snippets. Are you debugging while testing? If so, then this will not work properly as sytem OFF is not supporet while debugging. In that case emulated system off will be used, which is just an eternal loop.

[Mishka]

Hi Einar, thanks for the hint!

The app is not under debugger - connected just to the PPK.

However, running it under debugger shows that the board stuck in the NRF_LOG_FLUSH(). I've added it because I miss the "Power off" diagnostic message on console otherwise. After replacing the message with a trivial LED based monitor it's finally working:

Average idle current - 10 nA, max - 44 uA.

So it seems that nothing wrong with the power management code indeed. The NRF_LOG_FLUSH() might worth another post?