Queries on System OFF mode

[beemavishnu]

Hello,

 

I am using nRF52832, SDK_15.3.0, S132 SoftDevice and Segger for flashing the image. I am using ‘ble_app_blinky’.

I have few queries on System OFF mode.

 

1) What is the difference between calling directily sd_power_system_off() and calling nrf_pwr_mgmt_shutdown(). Whether DMA status will be check and then only go to sleep. Which function is better ?

a) In debug mode, whether calling nrf_pwr_mgmt_shutdown() is better as it has while(1) loop ?

 

2) What is the difference between NRF_PWR_MGMT_SHUTDOWN_GOTO_SYSOFF and NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF.

a) Its mentioned as “Useful when battery level is dangerously low”. What does it mean. In this case, will not controller wakeup if there is a GPIO event.

 

3) ble_app_blinky application is only with System ON mode. I want both System OFF and System ON mode. Initially my device will be in System OFF mode. When a button is pressed for 5sec then only I will enter into System ON mode. After some operations my device will go back to System OFF mode by setting bEnterSystemOffMode to true. Is below implementation fine ?

 

static void idle_state_handle(void)
{
    ret_code_t err_code;
    
    if(bEnterSystemOffMode == true)
    {
        // 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);
        
        //nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF);
    }
    else if (NRF_LOG_PROCESS() == false)
    {
        nrf_pwr_mgmt_run();
    }
}

Thanks & Regards

Vishnu Beema

[haakonsh]

1. nrf_pwr_mgmt_shutdown uses the Power Management library. You do not have to use it, it just has some added features.
   You need to make sure that you've completed all memory accesses before entering SystemOFF. Note that flash operations will halt the CPU until they are finished, so you do not need to be concerned with flash accesses.
   
2. I've asked the developers, waiting for a reply.
   
   
3. It looks alright.

[beemavishnu]

Thank you for your inputs.

I will wait for your response on Query 2.

[haakonsh]

I've gotten the reply:

The idea was pretty simple:

• NRF_PWR_MGMT_SHUTDOWN_GOTO_SYSOFF is a normal shutdown, in which one of hooks attached to power manager prepares device wake-up (for example by enabling GPIOTE).
• NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF is an emergency shutdown in which no wake-up should be configured. This in intended to be used in battery-low scenario, in which power usage has to be minimized to avoid battery leakage. When user replaces battery, system is being reset and returns to normal operation.

[beemavishnu]

Thank you for your inputs