Dynamically setting the LPCOMP REFSEL

RE: Dynamically setting the LPCOMP REFSEL

Rm3 — Fri, 21 Nov 2025 13:37:48 GMT

Hi Hung,

I've got it working now thanks to that thread. Thank you for sharing that.

Below is a working snippet for anyone else trying to do this (ncs v3.1.1 and NRF54L15)

No device overlay

prj.conf simply contains "CONFIG_NRFX_LPCOMP=y"

Main.c is:

#include <zephyr/kernel.h>

#include <zephyr/drivers/gpio.h>

#include <hal/nrf_lpcomp.h>

#include <hal/nrf_gpio.h>

#include <nrfx_lpcomp.h>

#include <nrfx_gpiote.h>

#include <nrfx.h>

static nrfx_lpcomp_config_t config =

NRFX_LPCOMP_DEFAULT_CONFIG(NRF_GPIO_PIN_MAP(1, 11));

static nrfx_err_t err;

static void lpcomp_event_handler(nrf_lpcomp_event_t event)

{

if (event == NRF_LPCOMP_EVENT_DOWN) {

printk("DOWN event! Lowering Threshold...\n");

// Shutdown LPCOMP to make changes

nrfx_lpcomp_disable();

nrfx_lpcomp_uninit();

// change reference

config.reference = NRF_LPCOMP_REF_SUPPLY_3_8;

// clear latched LPCOMP events before re-init

NRF_LPCOMP->EVENTS_DOWN = 0;

NRF_LPCOMP->EVENTS_UP = 0;

NRF_LPCOMP->EVENTS_CROSS = 0;

NRF_LPCOMP->EVENTS_READY = 0;

err = nrfx_lpcomp_init(&config, lpcomp_event_handler);

if (err != NRFX_SUCCESS) {

printk("nrfx_lpcomp_init error: %08x\n", err);

return;

}

nrfx_lpcomp_enable();

}

void main(void)

{

IRQ_DIRECT_CONNECT(COMP_LPCOMP_IRQn, 5, nrfx_lpcomp_irq_handler, 0);

// initial configuration

config.reference = NRF_LPCOMP_REF_SUPPLY_4_8;

config.detection = NRF_LPCOMP_DETECT_DOWN;

config.hyst = NRF_LPCOMP_HYST_ENABLED;

err = nrfx_lpcomp_init(&config, lpcomp_event_handler);

if (err != NRFX_SUCCESS) {

printk("nrfx_lpcomp_init error: %08x\n", err);

return;

}

nrfx_lpcomp_enable();

printk("LPCOMP initialized\n");

}

RE: Dynamically setting the LPCOMP REFSEL

Hung Bui — Fri, 21 Nov 2025 11:44:43 GMT

Hi Rhys,

Zephyr driver is not made for dynamically change the REFSEL. You may need to use what Jorg suggested.
I found a sample here LPCOMP in NCS-Zephyr on NRF52 It's quite old but I guess you can give it a try.

RE: Dynamically setting the LPCOMP REFSEL

Rm3 — Thu, 20 Nov 2025 15:18:25 GMT

Thanks, I tried to go down the nrf_lpcomp route but couldn't figure out how to get it to work, only examples I could find were Zephyr, using teh devicetree overlay to set it up. Would you have any examples on how to setup a simple lpcomp with the nrf/nrfx drivers?

Thanks again

RE: Dynamically setting the LPCOMP REFSEL

Turbo J — Thu, 20 Nov 2025 15:15:57 GMT

Dunno if its documented, but you can just #include <zephyr/drivers/comparator/nrf_lpcomp.h> in your source file.

This header exposes the functions required to (re-) configure the peripherial. There is another file nrf_lpcomp.h in the same folder for the low power comparator.