sd_power_system_off hardfault

[Syrius]

Hi,

There is a following initialization in 51822:

static void controls_init(void){

uint32_t err_code;
// Configure pins.
uint32_t pins_transition_mask = (1 << SCKIN_PIN) | (1 << WAKEUP_PIN) | (1 << SLEEP_PIN);

nrf_gpio_cfg_input(WAKEUP_PIN, NRF_GPIO_PIN_NOPULL);
nrf_gpio_cfg_input(SLEEP_PIN, NRF_GPIO_PIN_NOPULL);
nrf_gpio_cfg_input(SDAIN_PIN, NRF_GPIO_PIN_NOPULL);
nrf_gpio_cfg_input(SCKIN_PIN, NRF_GPIO_PIN_NOPULL);

err_code = app_gpiote_user_register(&m_gpiote_user_id,
								0x00,
								pins_transition_mask,
								gpiote_event_handler);

APP_ERROR_CHECK(err_code);
err_code = app_gpiote_user_enable(m_gpiote_user_id);
APP_ERROR_CHECK(err_code);

}

The event handler calling following code when sleep pin asserted:

				err_code = app_gpiote_user_disable(m_gpiote_user_id);
				APP_ERROR_CHECK(err_code);
				nrf_gpio_pin_clear(BLE_ACTIVE);
				nrf_gpio_pin_clear(ADV_PIN_NO);

				// Configure buttons with sense level low as wakeup source.
				nrf_gpio_cfg_sense_input(WAKEUP_PIN,
										 NRF_GPIO_PIN_NOPULL,
										 NRF_GPIO_PIN_SENSE_LOW);
				
				// Go to system-off mode (this function will not return; wakeup will cause a reset)                
				err_code = sd_power_system_off();
				APP_ERROR_CHECK(err_code);

It is similar to the adv_timeout in on_ble_evt but if it is called then controller goes into hardfault state. Could anybody know what's wrong? Advtimeout is working perfectly. I just wanted to put the controller into sleep mode from externally.

p.s.: how can I paste a code snipet properly here? It always formatted wrong... :s

[Stefan Birnir Sverrisson]

Hi. Where exactly are you getting the hardfault? Just as soon as you enter the handler, or when you call system off?

[Syrius]

when I call system off. I forgot to tell SD version as well: SD110 7.1.0

So the differences: when the controller go to sleep after advertising timeout I can wake up by wakeup pin. And if I push pause button in debugger it shows some instruction somewhere inside the SD. When I wanted to sleep by Sleep pin I can't wake up the device and if I push pause it shows hardfault handler.

[Stefan Birnir Sverrisson]

Hi

The reason for the hardfault is that the priority of the gpiote interrupt is set to APP_IRQ_PRIORITY_HIGH which is ARM priority 1. The gpiote interrupt handler calls your app_gpiote handler directly. When sd_* softdevice function is called (like the sd_power_system_off()) , it will call software interrupts with ARM priority 2. The rule is you must call sd_* function with a lower priority, i.e. from priority 3 (APP_IRQ_PRIORITY_LOW) or from main context, otherwise you will get a hardfault. See more about ARM priorities on this thread.

There are two solutions to this scenario:

1. Use the scheduler and call sd_power_system_off function from a scheduler handler which is executed in the main context (lowest priority)
2. Define the app_gpiote interrupt with priority APP_IRQ_PRIORITY_LOW (ARM priority 3) but that is not really recommended because that might delay the gpiote interrupt extensively. The app_gpiote library relies on that the gpiote interrupt is executed quicly.

So using the scheduler is recommended.

[Syrius]

Thank you for this teaching! It is working now!