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bogus
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June 18, 2024
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Nucleo-144 (F756ZG) stopped working after cut-off ST-Link

  • June 18, 2024
  • 3 replies
  • 2028 views

Hello, I recently bought Nucleo-144 board (variant F756ZG) to one of my project. I used DFU to upload firmware and external power supply using VIN pin (7.5 VDC). It works perfect until I decided to remove ST-Link part to reduce board size. After that it won't work anymore (no Serial COM, no Ethernet). Could someone help me what I am doing wrong? Maybe I should reconfigure jumpers but I don't know which. Below I attached photo of board.

Many thanks for help.

    This topic has been closed for replies.
    Best answer by AScha.3

    Hi,

    just look, if you still have a clock on the cpu....

    see circuit:

    AScha3_0-1718740644440.png

    Clock coming from MCO , st-link, but you cut it away: so change solder bridge SB8/9 (close) , sb149 cut.

    And set your HSE to crystal , 8MHz . (If you didnt this.)

    And check: is crystal and C37/38 really there ? Otherwise install , solder 8MHz crystal + 2x 4p7 there.

    From pic: X3 not there, so you have to solder...or just for check/run : set it on HSI , to get it working without crystal.

    AScha3_0-1718742490800.png

     

    3 replies

    T
    Tesla DeLorean
    Graduate II
    June 18, 2024

    No Serial COM? You mean from the ST-LINK/V2-1 VCP connection?

    You can find a schematic via the "CAD Resources" page for the product

    Check where the 5V source comes from in the VIN case, because the regulator is almost certainly a 3V3 one, not a means of getting 5V from the 7.5V you're injecting.

      A
      AScha.3Answer
      Super User
      June 18, 2024

      Hi,

      just look, if you still have a clock on the cpu....

      see circuit:

      AScha3_0-1718740644440.png

      Clock coming from MCO , st-link, but you cut it away: so change solder bridge SB8/9 (close) , sb149 cut.

      And set your HSE to crystal , 8MHz . (If you didnt this.)

      And check: is crystal and C37/38 really there ? Otherwise install , solder 8MHz crystal + 2x 4p7 there.

      From pic: X3 not there, so you have to solder...or just for check/run : set it on HSI , to get it working without crystal.

      AScha3_0-1718742490800.png

       

        T
        Tesla DeLorean
        Graduate II
        June 18, 2024

        The Ethernet has it's own TCXO / Crystal

        But yes the HSE might be an issue

        Instrument code, output something, or turn on RED LED if you go off and die in Error_Handler()

        Have something in HardFault_Handler() too

        A
        Andrew Neil
        Super User
        June 19, 2024

        So what debugging have you done to see what is happening?

        You can still use the broken-off ST-Link to debug and/or as a VCP - you just have to re-make all the necessary connections with wires.

         

        As the others have said, by default the Target MCU gets its clock from the ST-Link - so you're also going to have to do something about your clock source ...

         

        @bogus wrote:

        Maybe I should reconfigure jumpers but I don't know which. Below I attached photo of board.

        Many thanks for help.

        The User Manual describes all the jumpers and, as @Tesla DeLorean said, you can also look at the schematics...

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