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  • Case ID: 322122
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nRF52840DK COM port does not appear

zazas321

Hello. I have been experimenting with the nRF52840 and current consumption. I may have accidentally connected Li po battery terminals the other way around for a brief moment, also, I may have supplied around 4.0V via the External supply connector (I think the maximum voltage is 3.3V).

Is it possible that I caused damage to the interface MCU as I can no longer see the device COM port when plugged to USB? The screenshot of the nRF52840DK:

The nRF52840 CPU itself seems to be working fine. I can see that the led blinks every 1 second (previously I had the blinky program flashed) so it executes the code as expected, however, I cannot reprogram it since it does not detect any connected devices.

I have ordered another nRF52840DK but I am just curious about what could have happened..

  • +1

    Hello Lukas,

    First of all, there are multiple things that might be wrong. Have a look at this list here of things to try.

    I may have accidentally connected Li po battery terminals the other way around for a brief moment, also, I may have supplied around 4.0V via the External supply connector (I think the maximum voltage is 3.3V).

    I don't think that should be enough to fry anything.

    I see that you have some cables connected up to the current measurement pins there, and have presumably cut SB40. I am not sure if you would be able to connect to the debugger with that connected. Could you try disconnecting those cables, and use a jumper on the current measurement pins and see if it helps?

    Regards,

    Elfving

  • 0 in reply to Elfving
    Elfving said:
    I see that you have some cables connected up to the current measurement pins there, and have presumably cut SB40. I am not sure if you would be able to connect to the debugger with that connected. Could you try disconnecting those cables, and use a jumper on the current measurement pins and see if it helps?

    That is a jumper (I did not  have a proper jumper so just used a cable instead), see the full screenshot below:




    Going through the list if things to try as you have suggested:

    1. Does the device show up in Device Manager on your computer? Please try to connect and disconnect the kit a few times. It might show up with unexpected names.

    Nothing shows up on Device Manager.

    2.Have you tried a different USB cable? Faulty cables are surprisingly often the problem.

    Yes. Same problem

    3.Have you tried using a different computer? If it works on a different computer we know that the kit is not broken and that it is probably a driver issue.

    Problem is definately with the nRF52840DK as I have borrowed another nRF52840DK from colleague and tried with my PC and my USB cable and it works as expected. My broken DK does not work on any other PC'S.

    4. Have you tried to press the IF BOOT/RESET button while power cycling the kit? It should then show up as a Removable Storage Device named "BOOTLOADER". Then you can drag-and-drop the J-LINK interface MCU firmware found here (v170724) onto the storage device to reprogram the JLINK firmware.

    Problem fixed!!! After reprogramming the interface MCU the interface LED (led5) started blinking and after the reset the COM port appeared and I can use the device as usual.. Thanks!

  • +1 in reply to zazas321

    No problem Lukas! Slight smile

    Please let us know if there is anything else.

    Regards,

    Elfving

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