Nrf52840 Custom board peripherals not working....LED not blinking constantly

[A.A]

I designed a custom PCB using the nRF52840 based on Reference Circuitry Configuration 3 provided by Nordic. I followed the schematic exactly (see attached image), and I’ve verified that all power supply voltages (VBUS, VDD, VDDH, DEC pins, etc.) are correct and stable.

After flashing the firmware via SWD, the chip does not seem to function—there’s no response, and the LED blinks only while flashing the code sometimes but not constantly blinks as expected. I'm using the nRF52840-QIAA and flashing via SWDIO/SWDCLK. I’ve confirmed correct power to the chip and LED pull-up/down configuration.

What could be potential causes for the chip not running the firmware?

• Is there any additional required configuration not shown in the reference schematic?

• Could this be due to a bootloader or unprogrammed state of the chip?

Any suggestions would be greatly appreciated.

[mathiaso]

Hi, Ayesha.

I can see you're using a configuration without the inductors for the DC/DC regulator.

Please make sure you've disabled it by including the following in your devicetree.

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

Best regards,
Mathias