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nRF52811-QCAA-T not pre-programmed, soldered to board, not programmable

Kevin Jablonski

I hope, as a non-EE, I'm clear with my challenge ...

My student EE designed a small PCB with a couple of sensors (CO2, temp/humid, microphone) with an nRF52811. The boards were printed and assembled in China. We subsequently learned that the microprocessors soldered in place were not pre-programmed; therefore, our USB computer connection isn't recognizing the procssor/board. The solder points are under the chip.

Our board doesn't have any specific pads to use for programming.

Can anyone suggest what we might try to get our boards connected to our desktop for programming?  

Thank you!

Kevin Jablonski

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    Hi Kevin,

    The nRF52811 uses a two-pin SWD interface (SWDCLK + SWDIO) for programming.

    Since your student didn't put convenient programming pads on the PCB, there is a slight problem. But that doesn't mean you're stuck. The programming signals are already connected to certain pins (SWD interface) on the nRF52811. You may be able to find where those tiny copper tracks go on the PCB. If they pass through a small exposed hole (via), you can connect there. If not, someone experienced with PCB rework may be able to carefully scrape a tiny area of the track and solder a very thin wire to it.


    So, even without dedicated pads, you have a few options:

    1. Solder thin wire-wrap wires directly to the SWD pins on the chip package before or after carefully lifting it. This is delicate but possible with a steady hand and fine-tipped soldering iron.

    2. Use test points or vias — check your PCB layout files to see if SWDCLK or SWDIO traces are accessible anywhere on the board (e.g., at a via, resistor pad, or capacitor pad connected to those nets).

    3. Hot-air rework: Remove the chip, program it on a breakout or another board with SWD access, then reflow it back.

    Once you have physical access to SWDCLK and SWDIO, you can use a Nordic DK (e.g., nRF52840 DK or nRF52 DK) as a debug probe via its P19 or P20 debug-out connectors - no dedicated J-Link hardware needed.

    -Priyanka

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  • 0

    Hi Kevin,

    The nRF52811 uses a two-pin SWD interface (SWDCLK + SWDIO) for programming.

    Since your student didn't put convenient programming pads on the PCB, there is a slight problem. But that doesn't mean you're stuck. The programming signals are already connected to certain pins (SWD interface) on the nRF52811. You may be able to find where those tiny copper tracks go on the PCB. If they pass through a small exposed hole (via), you can connect there. If not, someone experienced with PCB rework may be able to carefully scrape a tiny area of the track and solder a very thin wire to it.


    So, even without dedicated pads, you have a few options:

    1. Solder thin wire-wrap wires directly to the SWD pins on the chip package before or after carefully lifting it. This is delicate but possible with a steady hand and fine-tipped soldering iron.

    2. Use test points or vias — check your PCB layout files to see if SWDCLK or SWDIO traces are accessible anywhere on the board (e.g., at a via, resistor pad, or capacitor pad connected to those nets).

    3. Hot-air rework: Remove the chip, program it on a breakout or another board with SWD access, then reflow it back.

    Once you have physical access to SWDCLK and SWDIO, you can use a Nordic DK (e.g., nRF52840 DK or nRF52 DK) as a debug probe via its P19 or P20 debug-out connectors - no dedicated J-Link hardware needed.

    -Priyanka

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