nrf52840 QFN48 pin debugging

RE: nrf52840 QFN48 pin debugging

luke1295 — Mon, 23 Feb 2026 17:25:31 GMT

Yes, the schematic and layout are good. I will try to design again QFN type with low oscillator and inductors for DCDC.

RE: nrf52840 QFN48 pin debugging

Kenneth — Sun, 22 Feb 2026 12:47:39 GMT

Have someone reviewed your schematic and layout? Maybe make a private case so someone can take a look.

I can't find anything specific wrong here, so maybe the hardware is outside of specifications.

Kenneth

RE: nrf52840 QFN48 pin debugging

luke1295 — Sat, 21 Feb 2026 09:43:28 GMT

devzone.nordicsemi.com/.../text_5F00_config2.txt devzone.nordicsemi.com/.../text_5F00_config.txt devzone.nordicsemi.com/.../8688.zephyr.dts

Sure, here are the files. I kept prj.conf as in the beginning. Also, I've tried in .overlay:

&reg1 {
	regulator-initial-mode = <0x0>;
};

&reg0 {
    status = "okay";
};

RE: nrf52840 QFN48 pin debugging

Kenneth — Thu, 19 Feb 2026 12:13:52 GMT

Can you share the updated zephyr.dts file(s) and .config file(s) after this change to make sure all are indeed set to 0x0 and also make sure all are using the internal RC oscillator.

Kenneth

RE: nrf52840 QFN48 pin debugging

luke1295 — Mon, 16 Feb 2026 18:51:47 GMT

Hi,
I've tried to modify in zephyr.dts regulator-initial-mode = < 0x0 >; and also in overlay file as:

&reg1 {
	regulator-initial-mode = <0x0>;
};

Also, dead in standalone power supply but alive in debug mode. Other possible causes to not starting?

RE: nrf52840 QFN48 pin debugging

Kenneth — Mon, 16 Feb 2026 11:59:06 GMT

Looking at the zephyr.dts I can find:

			/* node '/soc/power@40000000/regulator@40000578' defined in zephyr\dts\arm\nordic\nrf52840.dtsi:96 */
			reg1: regulator@40000578 {
				compatible = "nordic,nrf5x-regulator"; /* in zephyr\dts\arm\nordic\nrf52840.dtsi:97 */
				reg = < 0x40000578 0x1 >;              /* in zephyr\dts\arm\nordic\nrf52840.dtsi:98 */
				regulator-name = "REG1";               /* in zephyr\dts\arm\nordic\nrf52840.dtsi:99 */
				regulator-initial-mode = < 0x1 >;      /* in zephyr\boards\nordic\nrf52840dk\nrf52840dk_nrf52840.dts:150 */
			};

regulator-initial-mode seems to be set to NRF5X_REG_MODE_DCDC (=1) and not NRF5X_REG_MODE_LDO (=0).

Kenneth

RE: nrf52840 QFN48 pin debugging

luke1295 — Sat, 14 Feb 2026 21:43:10 GMT

UPDATE:

I managed to toggle physical pin 14 (P0.14) and 15 (P0.17) from the debugger. But when I power-on the chip standalone it doesn't start. I measured the correct voltages on DEC pins (stable voltages). I measured the nRESET pin and its 0V. No short on the PCB.

I observed a weird behavior. For a new chip, 1st use from reel, I can successfully connect from the debugger. After I flash the code, I cannot connect easily. I need to connect in the first second window after power-on the chip. I tried with J-Flash program (Connect option) and its the same story. Its something I broke after flashing by using nrfjprog commands? And that's why my chip seems to be dead in normal operation but in debug mode I can toggle the pins? Its something that keeps the chip into reset state?

RE: nrf52840 QFN48 pin debugging

luke1295 — Tue, 10 Feb 2026 19:49:39 GMT

devzone.nordicsemi.com/.../Copy2_2E00_config

RE: nrf52840 QFN48 pin debugging

luke1295 — Tue, 10 Feb 2026 19:48:11 GMT

devzone.nordicsemi.com/.../Copy_2E00_config

Dts here: devzone.nordicsemi.com/.../4380.zephyr.dts

Sure. I found 2x .config. One in: project_name/build/project_name/zephyr and one in: project_name/build/zephyr

RE: nrf52840 QFN48 pin debugging

Kenneth — Tue, 10 Feb 2026 19:29:16 GMT

Can you share the .config and zephyr.dts files from your build folder?

Kenneth

RE: nrf52840 QFN48 pin debugging

luke1295 — Tue, 10 Feb 2026 18:52:02 GMT

Hi,

I've tried the following code for multiple GPIO:

#define PIN_P0_13 13
#define PIN_P0_14 14
#define PIN_P0_15 15
#define PIN_P1_15 38

int main(void)
{
    const struct device *gpio0 = DEVICE_DT_GET(DT_NODELABEL(gpio0));
    const struct device *gpio1 = DEVICE_DT_GET(DT_NODELABEL(gpio1));

    if (!device_is_ready(gpio0) || !device_is_ready(gpio1)) {
        return 0;
    }


    gpio_pin_configure(gpio0, PIN_P0_13, GPIO_OUTPUT_INACTIVE);
    gpio_pin_configure(gpio0, PIN_P0_14, GPIO_OUTPUT_INACTIVE);
    gpio_pin_configure(gpio0, PIN_P0_15, GPIO_OUTPUT_INACTIVE);
    gpio_pin_configure(gpio1, PIN_P1_15, GPIO_OUTPUT_ACTIVE);

    while (1) {
        gpio_pin_set(gpio0, PIN_P0_13, 1);
        gpio_pin_set(gpio0, PIN_P0_14, 1);
        gpio_pin_set(gpio0, PIN_P0_15, 1);
        gpio_pin_set(gpio1, PIN_P1_15, 1);
        k_msleep(500);

        gpio_pin_set(gpio0, PIN_P0_13, 0);
        gpio_pin_set(gpio0, PIN_P0_14, 0);
        gpio_pin_set(gpio0, PIN_P0_15, 0);
        gpio_pin_set(gpio1, PIN_P1_15, 0);
        k_msleep(500);
    }
}

On DK the code is working since LED1, LED2 and LED3 are blinking. On QFN nothing happens. My overlay file is called: nrf54h20dk_nrf54h20_cpuppr.overlay and the content is this:

&reg1 {
	regulator-initial-mode = <NRF5X_REG_MODE_LDO>;
};

&reg0 {
    status = "okay";
};

I've tried to enter in debug mode both for DK and for connected QFN. I can step each line without any error. Is something I'm missing about GPIO when I'm migrating the code on QFN?

Luke

RE: nrf52840 QFN48 pin debugging

Kenneth — Tue, 10 Feb 2026 09:22:09 GMT

Hello,

If you have problems with a specific GPIO, my first suggestion for test would be to try a different GPIO.

The firmware should be able to run on both DK and your board, does it work as intended on the DK?

Also look a the .config and zephyr.dts file from the build folder, is it possible that P0.13 is already use for LED or similar?

If you try to debug your project in vs code, can you single step the project to see if it faults or execute as expected?

Kenneth