Blinky Example on nRF52840 Custom Board

RE: Blinky Example on nRF52840 Custom Board

EE Michael — Sat, 25 Jul 2026 20:49:40 GMT

Hi Hung,

I really appreciate the feedback so far. I suspect that my reflow process was suspect since a few pads were compromised when I removed the nrf52840 IC.

I ended up populating a new board, and everything is working as expected.

Thanks again for bouncing some ideas around.

EEM

RE: Blinky Example on nRF52840 Custom Board

Hung Bui — Thu, 23 Jul 2026 13:41:14 GMT

Hi Michael.
My tip is to test on a DK. If you don't see the issue on the DK then it must be something wrong with the PCB.

Please check the circuit you connet to P0.08, check how much current it's drawing if you set it to 3V.

RE: Blinky Example on nRF52840 Custom Board

EE Michael — Wed, 22 Jul 2026 18:48:07 GMT

Hi Hung,

I removed series resistors to disconnect the various GPIOs, and I measured a square waveform that swings between VDD and GND on most of the GPIO; exceptions were P0.14 and P0.24.

On the left hand quadrant, P0.08, P1.08, P1.09, P0.11 were able to push/pull to VDD/GND.

On the bottom quadrant, P0.13, P0.19(ext pullup), P0.20(ext pullup) were able to push/pull to VDD/GND. However, P0.14 and P0.24 were 0VDC.

If I do reconnect the circuit of P0.08, there is a square wave, but the VOH level is attenuated dramatically to <1V.

I am not sure why the GPIOs are so sensitive. The I/O are intended for digital peripherals SPI, I2C, and single LED.

Do you think I need to remove the IC, clean up the pads, and attempt to solder? I am using the 48pin QFN, suffix QFAA.

What are your thoughts?

Thanks,

Michael

RE: Blinky Example on nRF52840 Custom Board

EE Michael — Tue, 21 Jul 2026 21:07:37 GMT

Hi Hung,

I appreciate your feedback. I included my customBoard.dts and started to delete a few 'properties' or disable certain things in attempt to resolve the issue.

I can disconnect the circuit elements, and retest the problematic pins. I'll report back on your recommended hardware troubleshooting this evening.

I did go back and verify the layout with one of my spare boards via continuity. Additionally, I also tested the LED to make sure it was connected correctly cathode pointing to P0.24 and verified component functionality using DMM diode test function. I'm hoping it is just DT conflict, but there may be an unintended connection.

Much appreciated,

EEM

devzone.nordicsemi.com/.../customBoard.dts devzone.nordicsemi.com/.../2605.prj.conf

RE: Blinky Example on nRF52840 Custom Board

Hung Bui — Tue, 21 Jul 2026 20:10:39 GMT

Hi EEM,

Please check the device tree configuration. I suspect that the pins may be used in other peripheral causing the pins to behave differently.

Please try to disconnect the pins from the series resistor and measure again to double check if the output match 3.3V. You can also test by connecting the button pins on the DK to the custom board and check if the voltage level is correct.

Please attach your device tree so we can take a look.