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VVV
Explorer
May 14, 2025
Solved

NUCLEO-H723ZG 3V3 power (no PWR jumpers) and simultaneous USB STLINK-V3E debugging

  • May 14, 2025
  • 1 reply
  • 447 views
I have a "NUCLEO-H723ZG" dev board. My current configuration is to power the dev board by 3V3 (CN8 pin 7 or CN11 pin 16), with all jumpers from the "PWR JP2" removed, as according to section "6.4.5 External power supply input from 3V3_EXT (3.3 V)" of the "UM2407 STM32H7 Nucleo-144 boards (MB1364)" document.

In that section it says:

"When the 3.3 V is provided by a shield board, it is worthy to use the 3V3 (CN8 pin 7 or CN11 pin 16) directly as power input (refer to Table 9 and Figure 4). In this case, programming and debugging features are not available, since the STLINK-V3E is not powered."

Is there any way at all to safely program / debug / access the virtual COM port routed though the USB connector when the Nucleo is simultaneously powered by 3V3 (CN8 pin 7 or CN11 pin 16)? In other words, is it safe to have the USB cable attached at the same time as the board is receiving 3V3 power as well?

There is a section "6.4.6 Debugging while using VIN or EXT as an external power supply", but it does not apply as I am not using "VIN" or "EXT". In that section, there is a sequence of 5 steps if you want to debug / program while "VIN" or "EXT" is used.
    This topic has been closed for replies.
    Best answer by EZHON.1

    Hello,

    Generally speaking, when we use the external 3V3 from connectors (CN8 pin 7 or CN11 pin 16), we don't need the power supply from STLINK though the USB connector. That means, the communication from STLINK or the virtual com are disable.

    Of course, you can connect the USB cable as STLINK side power supply. At the same time, the external 3V3 from connectors (CN8 pin 7 or CN11 pin 16) when JP2 isn't mounted. it's safe for different power supply.

    Please double check the MB1364-H723ZG-E01 Schematics for your application.

     

    B.R

    Eric

    1 reply

    E
    EZHON.1Answer
    ST Employee
    May 15, 2025

    Hello,

    Generally speaking, when we use the external 3V3 from connectors (CN8 pin 7 or CN11 pin 16), we don't need the power supply from STLINK though the USB connector. That means, the communication from STLINK or the virtual com are disable.

    Of course, you can connect the USB cable as STLINK side power supply. At the same time, the external 3V3 from connectors (CN8 pin 7 or CN11 pin 16) when JP2 isn't mounted. it's safe for different power supply.

    Please double check the MB1364-H723ZG-E01 Schematics for your application.

     

    B.R

    Eric

      V
      VVVAuthor
      Explorer
      May 15, 2025

      Thanks Eric, this is very informative. I will keep the dev board powered by 3V3 with no jumpers, and plug in the USB as needed for debugging and programming.

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