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Andrew Neil
Andrew Neil
Super User
Jun 9, 2025 3:07 PM UTC
Solved

Documentation Omission: IDD polarity on Nucleo-64 Boards (UM1724)

AndrewNeil_0-1749481538098.png

AndrewNeil_1-1749481581638.png

 

There's nothing in the manual which tells you which pin is source, and which is load!

 

PS:

Even the schematic doesn't help!

AndrewNeil_0-1749481849863.png

 

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Mike_ST
Mike_STBest answer
ST Technical Moderator
Jun 10, 2025 9:49 AM UTC

Hello,

There is an ongoing effort to fix this on the newer designs.

Some boards have the pin "1" indication around the IDD jumper, but the schematic forget to tell which one is pin 1... 

Some board have "VDD_MCU" marking on one pin, which make it clear.

 

For that  particular board (MB1136), it is an old design, the chances that we roll out an update for that one are low.

Anyways I entered a ticket to add some indication in case it happens:

Internal ticket : #211869

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10 replies

mƎALLEm
mƎALLEm
ST Technical Moderator
Jun 9, 2025 3:20 PM UTC

Hello,

I don't think this is something critical or blocker as connecting the ammeter in different polarity gives the same power consumption value but with different sign.

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    Andrew Neil
    Andrew NeilAuthor
    Super User
    Jun 9, 2025 3:38 PM UTC

    Indeed, if you're just using a digital ammeter or DMM, the sign will tell you if you have it the right way around.

    But a DMM really isn't a very useful tool - it can't show rapid variations.

    It can't even show you the 100ms on/off of the LED in the standard demo code.

    For that, you need some sort of proper power analyser - and then you do need to know which way around to connect it!

    AndrewNeil_0-1749483504529.png

     

    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
    Peter BENSCH
    Peter BENSCH
    ST Technical Moderator
    Jun 9, 2025 3:43 PM UTC

    Well, if you want to operate the target without STS-LINK/V2-1 and only want to feed in there, this may play a role. However, according to schematics, the left pin of JP6 here is VDD, which can also be found on CN7.5.

    However, the GERBER also shows the connections, e.g. as in the following picture, in which I have marked the tracks in colour:

    • +3V3 = red
    • VDD = dark green

    But @Andrew Neil surely means that this could also be in the UM1724.

    mb1136_JP6.png

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    Andrew Neil
    Andrew NeilAuthor
    Super User
    Jun 9, 2025 3:50 PM UTC

    I couldn't find the PCB layout as a PDF on the CAD Resources page - just Gerbers & Schematics

    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
    Peter BENSCH
    Peter BENSCH
    ST Technical Moderator
    Jun 9, 2025 5:54 PM UTC

    I don't really understand the problem - any PDF viewer can do PDF, but it is static, you only see the default view. GERBER can be used by any GERBER viewer, which is also available free of charge, e.g. as part of KiCAD, where, unlike PDF, you can select the layers to be displayed and their colours?

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    Andrew Neil
    Andrew NeilAuthor
    Super User
    Jun 9, 2025 3:54 PM UTC

    AndrewNeil_1-1749484440620.png

     

     

    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
      mƎALLEm
      mƎALLEm
      ST Technical Moderator
      Jun 9, 2025 3:59 PM UTC
      @Andrew Neil wrote:

      AndrewNeil_1-1749484440620.png

       

       

      From my standpoint this is something that could be indicated by silkscreen on the PCB.

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        Andrew Neil
        Andrew NeilAuthor
        Super User
        Jun 9, 2025 4:16 PM UTC

        Absolutely: I think it should be indicated - either on the silkscreen, or by the usual indication of "Pin 1" of the header by a square pad.

         

        (as seen for JP5 in the image posted by @Peter BENSCH)

        A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
          Mike_ST
          Mike_STBest answer
          ST Technical Moderator
          Jun 10, 2025 9:49 AM UTC

          Hello,

          There is an ongoing effort to fix this on the newer designs.

          Some boards have the pin "1" indication around the IDD jumper, but the schematic forget to tell which one is pin 1... 

          Some board have "VDD_MCU" marking on one pin, which make it clear.

           

          For that  particular board (MB1136), it is an old design, the chances that we roll out an update for that one are low.

          Anyways I entered a ticket to add some indication in case it happens:

          Internal ticket : #211869

          In order to give better visibility on the answered topics, please click on 'Best answer' on the reply which solved your issue or answered your question. 
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