Can't reach low power with zephyr's GPIO API

RE: Can't reach low power with zephyr's GPIO API

Håkon Alseth — Mon, 15 Dec 2025 14:06:52 GMT

Hi,

[quote user="narfster"]a. what is the max number of sense pins i can use.[/quote]

PORT can be used on all capable GPIOs (P0/P1 in this case).

[quote user="narfster"]b. When should developer use sense pins, when should he prefer the default behavior. (not low power) [/quote]

SENSE (using PORT event) is level triggered, as compared to edge-triggered with GPIOTE_IN channel.

A GPIOTE IN channel can generate individual events, and can be used to tie it together with other events via DPPI.

SENSE (PORT) is usually used for wake-up scenarios, while GPIOTE IN is used for more precise timing.

[quote user="narfster"]c. is there a restriction on what gpio pins to use for sense. i.e. is P2.x supported for GPIOTE sense?[/quote]

On the nRF54Lxx-series devices, you can use GPIOTE SENSE (PORT event) on P0 and P1 based GPIOs, but P2 does not have any sense/GPIOTE functionality:

https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/gpio.html#ariaid-title4

Kind regards,

Håkon

RE: Can't reach low power with zephyr's GPIO API

narfster — Mon, 15 Dec 2025 11:56:02 GMT

Follow up question, for completion.

a. what is the max number of sense pins i can use.

b. When should developer use sense pins, when should he prefer the default behavior. (not low power)

c. is there a restriction on what gpio pins to use for sense. i.e. is P2.x supported for GPIOTE sense?

RE: Can't reach low power with zephyr's GPIO API

narfster — Mon, 15 Dec 2025 11:52:53 GMT

Added this into the device tree sense-edge-mask.
It did the job. Thanks.
Documentations is very poor. 
Expected this basic option to be enabled and supplied with nrf connect SDK.
wasted hours on this, on contrary using nrfx gpiote API - 
worked immediately out of the box and it took 15 minutes. 
#define PAD_BTN_GPIO_SPEC       <&gpio1 8  (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>
&gpio1 {
    sense-edge-mask = <0x00002100>; /* P1.08 and P1.13 */
};

    button_in:button_in {
        compatible = "gpio-keys";
        debounce-interval-ms = <150>;                      /* Debouncing time */
        button: button {
            gpios = PAD_BTN_GPIO_SPEC;
            label = "pad_btn";
            zephyr,code = <INPUT_KEY_2>;
        };
    };

RE: Can't reach low power with zephyr's GPIO API

Turbo J — Sun, 14 Dec 2025 16:56:02 GMT

Pretty sure this is intended behaviour, but it may not be properly documented.

GPIOTE "in" events are more expensive than "port" events. But "port" events only support level detection - your code sets up edge detect which requires "in" event.

I can't find documentation on how much current this is supposed to cost extra.

Workaround is to use the "sense" mechanism (I believe you can set this up in DT overlay) and "level" triggered GPIO interrupt.

Note: Just setting up level triggers for the GPIO int is not enough, the pin must also be set up correctly (sense-edge-mask).

RE: Can't reach low power with zephyr's GPIO API

narfster — Sun, 14 Dec 2025 09:38:08 GMT

overlay:

#define PAD_IN_GPIO_SPEC        <&gpio1 13 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>

    pad_input:pad_input {
        compatible = "gpio-keys";
        debounce-interval-ms = <150>;                      /* Debouncing time */
        pad_state_in: pad_state_in {
            gpios = PAD_IN_GPIO_SPEC;
            label = "pad_signal_in";
            zephyr,code = <INPUT_KEY_0>;
        };