GPIO state not retained after FOTA reboot on nRF54L15 (Zephyr SDK 3.0.2)

[Jishnu K J]

Hi,

I am using nRF54L15 with Zephyr RTOS in nRF Connect SDK v3.0.2.

After performing a FOTA update, the device reboots. I need to retain the state of a GPIO pin across this reboot.

The GPIO I am trying to retain is P1.06. I attempted to configure it with retention using the following code:

#define PIN_P1_06 38
#define P1_INDEX  6

void configure_retained_gpio(void) {
    // Configure the pin as output with retention enabled
    nrf_gpio_cfg_output(PIN_P1_06);
 
    NRF_P1->PIN_CNF[P1_INDEX] &= ~GPIO_PIN_CNF_CTRLSEL_Msk;
    NRF_P1->PIN_CNF[P1_INDEX] |= (GPIO_PIN_CNF_CTRLSEL_GPIO << GPIO_PIN_CNF_CTRLSEL_Pos);
}

However, after the OTA update and subsequent reboot, the GPIO state is cleared and does not retain the previous value.

My questions:

1. Is there any additional configuration required in nRF54L15 to retain GPIO states across a reboot after FOTA?

2. Is GPIO retention supported across MCU reset triggered by FOTA, or is it only supported for specific low-power modes?

Any guidance or recommended approach to preserve the GPIO state across OTA reboot would be greatly appreciated.

Thanks.

[Menon]

hello,

Since you are using NCS v3.0.2, I assume you are working with sysbuild. In that case, creating a child_image folder is not the correct approach for configuring MCUboot. Instead, you should create a sysbuild folder and include an mcuboot.overlay file there. Please refer to this sample, which demonstrates how to configure the bootloader.

Kind Regards,

Abhijith

[Jishnu K J]

Hi Abhijith,

I followed your suggestion and configured the bootloader using the sysbuild approach. I created a sysbuild folder and added both mcuboot.overlay and mcuboot.conf, similar to the sample you shared.

After building, I can confirm that the overlay is being applied correctly. I verified this in build/mcuboot/zephyr/zephyr.dts, where the GPIO hog is present:

gpio1: gpio@d8200 {
    compatible = "nordic,nrf-gpio";
    gpio-controller;
    reg = < 0xd8200 0x300 >;
    #gpio-cells = < 0x2 >;
    ngpios = < 0x10 >;
    status = "okay";
    port = < 0x1 >;
    gpiote-instance = < &gpiote20 >;
    phandle = < 0x11 >;

    load_cell_en_hog: load-cell-en-hog {
        gpio-hog;
        gpios = < 0x6 0x0 >;
        output-high;
        line-name = "load-cell-enable";
    };
};

However, in our case, it still does not work. After the firmware update, the GPIO pin P1.06 is cleared, and the device powers off.

Best regards,

Jishnu K J