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  • Case ID: 296514
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2 virtual com cdc ports

Jiri Husak

Dear Support,

I just received  2 nRF52840 DKs (PCA10056) rev 3.0.0. When I plug them to Windows machine I see 2 COM ports ennumerated (JLink CDC UASRT Port) instead of one as I was used on previous versions of the DK. 

On top it seems non of the COM port works.

Could you please describe why there are 2 and what is the purpose? 

I searched the documentation but it's from 2020 here https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_nrf52840_dk%2FUG%2Fdk%2Fintro.html 

Thanks for help.

BR,

Jiri

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  • +1

    Hi Jiri Husak,

    Unfortunately the two COM ports problem is a known issue with the revision 3.0.0 of the nRF52840 DK, and there doesn't seem to be a work around for it yet. You could read more about the issue and workarounds in this Q&A:  nRFDK52 revision 3.0.0 reports two identical JLink CDC UART port . It is for the nRF52 DK but the information should still be true for the nRF52840 DK.

    Regarding your comments that none of the COM port work, what happened that lead you to believe so? May I suggest you to try a simple hello world sample to see if it is printing anything?

    Best regards,

    Hieu

  • 0 in reply to Hieu

    Thank you Hieu for your answer,

    so how is it inteded to work? Both of them shoudl work? only one? 

    I also noticed that flashing over Drag&Drop feature to JLINK drive fails 

    I just made the test with uart exaple - indeed it works (on one of the 2 CDCs) - there must be something else with our own SW, that works fine on older type of kit. 

    Thanks for your support.

    Jiri

  • 0 in reply to Jiri Husak

    Hi Jiri,

    Jiri Husak said:
    so how is it inteded to work? Both of them shoudl work? only one? 

    Only the one that you see printing stuff works.
    If you are using our VS Code Extension, it should show as VCOM0 in the Connected Device window.

    Jiri Husak said:
    I also noticed that flashing over Drag&Drop feature to JLINK drive fails 

    I just give Drag & Drop flashing a try. And it failed with the following FAIL.TXT file content:

    The currently active SWD interface does not support MSD drag and drop

    So unfortunately Drag & Drop isn't supported, at the least on the revision 3.0.0 nRF52 & nRF52840 DKs.

    Jiri Husak said:
    I just made the test with uart exaple - indeed it works (on one of the 2 CDCs) - there must be something else with our own SW, that works fine on older type of kit. 

    It shouldn't be like that... The pins should be the same... What is the older kit that you tested on? Older revision of the nRF52840? Are we sure the HWFC settings are correct?

    Best regards,

    Hieu

  • 0 in reply to Hieu

    Hi Hieu,

    thanks, so if I do 

    PS C:\> nrfjprog --com
    1050237188 COM14 VCOM0
    1050237188 COM15 VCOM1

    the one working is always the VCOM0 ?

    There was probably my fault - our old SW works now with the new kit if I select the proper com port. 

    Well I must say the new relese 3.0.0 doesn't bring really an improvement Slight smile

    BR,

    Jiri

Reply Children
  • 0 in reply to Jiri Husak

    Hi Jiri,

    Yes! What you do is exactly the other way to find the port that I cannot recall this morning.

    Good to know your SW works now.

    Unfortunately, I have to agree that revision 3.0.0 of the board doesn't bring an improvement at least as far as COM ports and debugging goes. Sorry you had to go through workarounds and keep all these extra trivia on your mind. I will inform the DK team of your and my opinions about this though.

    Happy dev'ing!

    Hieu.

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