nRF5 SDK System power off MODE wake up issue.

[Theja]

Hi,

I'm working on an application where the system should enter System OFF mode after some button activity and wake up (restart) on a button press or USB connection.

When I flash the application using Segger Embedded Studio, it works as expected. However, when I flash the combined HEX file (containing the bootloader, application, and SoftDevice) generated using the post-build commands, it only wakes up from the button press. If I connect the USB while in System OFF mode, it enters an unknown state where nothing functions.

I compared the HEX files — one read back from the device (flashed via IDE) and the other generated through the post-build commands — and found differences.

Here are the post-build commands I'm using:
call nrfutil settings generate --family NRF52840 --application CenSyn_EEG.hex --application-version 1 --bootloader-version 1 --bl-settings-version 2 bootloader_settings.hex
call mergehex --merge bootloader_settings.hex secure_bootloader.hex --output Combined_bootloader.hex
call mergehex --merge s140_nrf52_7.2.0_softdevice.hex Combined_bootloader.hex --output SD_FBL.hex
call mergehex --merge CenSyn_EEG.hex SD_FBL.hex --output Final_Hex.hex
call nrfutil pkg generate --hw-version 52 --application-version 2 --application CenSyn_EEG.hex --sd-req 0x100 --key-file private.key CenSyn_EEG_DFU.zip

How can I resolve this issue? Any insights would be greatly appreciated.

Regards,
Theja.

[Vidar Berg]

Hello Theja,

If I connect the USB while in System OFF mode, it enters an unknown state where nothing functions.

Please run 'nrfjprog --readregs' when the chip is in this state to see if the register readout may reveal what state the device is in.

I compared the HEX files — one read back from the device (flashed via IDE) and the other generated through the post-build commands — and found differences.

Does the application region in flash contain different data when you check the flash contents after using these two different methods?

nrfjprog --memrd 0x0 --n 0x1000000 > memory_content.txt

call nrfutil settings generate --family NRF52840 --application CenSyn_EEG.hex --application-version 1 --bootloader-version 1 --bl-settings-version 2 bootloader_settings.hex
call mergehex --merge bootloader_settings.hex secure_bootloader.hex --output Combined_bootloader.hex
call mergehex --merge s140_nrf52_7.2.0_softdevice.hex Combined_bootloader.hex --output SD_FBL.hex
call mergehex --merge CenSyn_EEG.hex SD_FBL.hex --output Final_Hex.hex
call nrfutil pkg generate --hw-version 52 --application-version 2 --application CenSyn_EEG.hex --sd-req 0x100 --key-file private.key CenSyn_EEG_DFU.zip

Is there a flash command that comes after this?

Thanks,

Vidar

[Theja]

Hi,

Apologies for the delayed response. I’ve read the registers while the device was in the unknown state, and I’ve attached the data below for your reference.

R0: 0x00025F40
R1: 0x2003FFB8
R2: 0x00000000
R3: 0x00000000
R4: 0x200000B8
R5: 0x00000000
R6: 0xE000E000
R7: 0x00000000
R8: 0x00000000
R9: 0x00000000
R10: 0x00000000
R11: 0x00000000
R12: 0x2003FF80
SP: 0x2003FFB8
LR: 0x0001671D
PC: 0x00025F40
xPSR: 0x61000000
MSP: 0x2003FFB8
PSP: 0x00000000
RAZ: 0x00000000
CFBP: 0x00000000
APSR: 0x60000000
EPSR: 0x01000000
IPSR: 0x00000000

Also, please note a few changes compared to previous observations. The device tends to enter the unknown state after being connected to USB. This behavior appears to be random and is not specific to the IDE or the hex file — it's occurring in both cases approximately 5 to 6 times out of 10.

I’ve also attached the schematic for your reference.POWER_SCH (1).pdf

To set the GPIO output to 3.3V, I made the following changes. Could this have anything to do with the issue?

    {
        NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen;
        while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}

        NRF_UICR->REGOUT0 = (NRF_UICR->REGOUT0 & ~((uint32_t)UICR_REGOUT0_VOUT_Msk)) |
                            (UICR_REGOUT0_VOUT_3V3 << UICR_REGOUT0_VOUT_Pos);  

        NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren;
        while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
    }

[Vidar Berg]

Hi,

The readout shows that the program has entered the wait for event loop inside the softdevice which is where a typical application will spent most of its time in. This loop is entered when the application or bootloader calls sd_app_evt_wait(). Are you able to check if the device may be entering bootloader DFU mode after the wake up?

[Theja]

Hi, 

Vidar Berg said:

Are you able to check if the device may be entering bootloader DFU mode after the wake up?

No, after waking up, it enters the application and works as expected.

To ensure we're on the same page, let me repeat the issue we're facing:

Using a button action, I put the device into deep sleep (system OFF mode). Before entering deep sleep, I configure the button as a wake-up source.

The problem is that after entering deep sleep, when I connect the USB, the device wakes up immediately in some cases, but other times it takes over 5 minutes to wake up (the timing varies). Once the device wakes up—even after the delay—it works as expected.

I’ve attached the deep sleep-related code for your reference.

void enter_deepSleep()
{
    ret_code_t  err_code;
    
    nrf_gpio_pin_clear(SHDN);
    nrf_gpio_cfg_input(SHDN, NRF_GPIO_PIN_NOPULL);

    nrf_drv_gpiote_in_uninit(BUTTON_PIN_NO);             //UnInitialize the wake-up pin

    turn_off_LED(GREEN);
    turn_off_LED(BLUE);
    turn_off_LED(RED);
   
    nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_TOGGLE(false);     //Configure to generate interrupt and wakeup on pin signal low. "false" means that gpiote will use the PORT event, which is low power, i.e. does not add any noticable current consumption (<<1uA). Setting this to "true" will make the gpiote module use GPIOTE->IN events which add ~8uA for nRF52 and ~1mA for nRF51.
    in_config.pull = NRF_GPIO_PIN_PULLUP;                                            //Configure pullup for input pin to prevent it from floting. Pin is pulled down when button is pressed on nRF5x-DK boards, see figure two in http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52/dita/nrf52/development/dev_kit_v1.1.0/hw_btns_leds.html?cp=2_0_0_1_4
   
    err_code = nrf_drv_gpiote_in_init(BUTTON_PIN_NO, &in_config, NULL);             //Initialize the wake-up pin
    APP_ERROR_CHECK(err_code);                                                       //Check error code returned
    
    nrf_drv_gpiote_in_event_enable(BUTTON_PIN_NO, true);                            //Enable event and interrupt for the wakeup pin   
    
    //StartBlinkTimer(BlinkThrice);
    nrf_delay_ms(2000);
    NRF_POWER->SYSTEMOFF = 1;
}

Also, please note that I haven’t done any explicit USB wake-up configuration during deep sleep, as the controller is already connected to USB VBUS.

regards,
Theja

[Vidar Berg]

Theja said:

No, after waking up, it enters the application and works as expected.

I'm asking about the failing case.