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Pratham1
Explorer
November 13, 2025
Solved

STM32H750B-DK: UART Pin Availability and Configuration

  • November 13, 2025
  • 2 replies
  • 218 views

Hello ST Community,

I’m currently working with the STM32H750B-DK development board and I’m facing an issue with UART communication through external pins.

My goal is to communicate between the STM32H750B-DK and another external controller using UART (not via the Virtual COM Port over USB).

Here’s what I have done so far:

  • I have configured USART3 (TX = PB10, RX = PB11) in STM32CubeMX for asynchronous communication.

  • I also tried USART2 (TX = PD5, RX = PD6), which are available on the STMod+ connector.

  • The code builds and runs successfully.

  • I can transmit data successfully via VCP (USB) and see it on the PC serial monitor.

  • However, when I connect a TTL-to-USB converter or logic analyzer to PB10/PB11 or PD5/PD6, I do not see any UART activity.

  • I have verified the pin configuration in CubeMX and ensured no alternate functions are conflicting.

It seems like the USART2/USART3 pins might not be physically routed to the external connectors on the STM32H750B-DK board, or they may be multiplexed with other onboard devices.

Could you please confirm:

  1. Which UART pins are actually available for external use on the STM32H750B-DK?

  2. Are USART2 (PD5/PD6) or USART3 (PB10/PB11) accessible through any connector (Arduino, STMod+, or CNx headers)?

  3. If not, what is the recommended way to use UART communication with another external controller on this board?

Any guidance or schematic reference would be greatly appreciated.

Best Regards,

Pratham Salunkhe

    This topic has been closed for replies.
    Best answer by mƎALLEm

    Hello,

    You need to check either the user manual of the board or the schematics.

    Here is the STMmod+ connector from the schematics:

    USART2 is not connected to that connector over PD5 and BD6 since the solder bridges SB12 and SB16 are not connected by default:

    mALLEm_0-1763029277104.png

    You need to solder them.

    2 replies

    G
    gbm
    Graduate
    November 13, 2025

    Check for switched TX/RX - UART TX should be connected to USB-UART RX pin. Also, check the ground connection.

    M
    mƎALLEmAnswer
    Technical Moderator
    November 13, 2025

    Hello,

    You need to check either the user manual of the board or the schematics.

    Here is the STMmod+ connector from the schematics:

    USART2 is not connected to that connector over PD5 and BD6 since the solder bridges SB12 and SB16 are not connected by default:

    mALLEm_0-1763029277104.png

    You need to solder them.

      P
      Pratham1Author
      Explorer
      November 17, 2025

      hello @mƎALLEm ,

      Thank you for your reply. By connecting the solder bridges, I could able to use the UART.

      Thank you for your time and support.

      Regards,

      Pratham

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