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avatar_ang
Associate
Feb 14, 2026 2:30 PM UTC
Solved

UART doesn't work on STM32F407G-DISC1

Hello
I'am new to STM32 and i want to create project that interface with user using uart with serial monitor
i  configured usart and used hal_uart tarsnmit function but it didnt work when the tutorial im following worked for him
what can be the issue?

Gyessine
GyessineBest answer
ST Technical Moderator
Feb 15, 2026 2:23 PM UTC

Hello @avatar_ang  and welcome to STcommunity!
can you explain how are you trying to print your messages  in serial monitor?
in the STM32F407G-DISC1 ,the ST-Link embedded in the F407 discovery is not wired to a target MCU UART, so it has no virtual COMPORT capability.(the physical connection is missing.) you will need to add physical link wires to the Discovery board or connect to a separate USB-to-UART adaptor.
Maybe this is your issue.

Gyessine_0-1771165345343.png

If this isn't your issue , please provide more informations
BR
Gyessine

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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5 replies

gbm
gbm
Super User
Feb 15, 2026 9:33 AM UTC

What kind of help you expect without providing any code or schematic?

My STM32 stuff on github - compact USB device stack and more: https://github.com/gbm-ii/gbmUSBdevice
    Gyessine
    GyessineBest answer
    ST Technical Moderator
    Feb 15, 2026 2:23 PM UTC

    Hello @avatar_ang  and welcome to STcommunity!
    can you explain how are you trying to print your messages  in serial monitor?
    in the STM32F407G-DISC1 ,the ST-Link embedded in the F407 discovery is not wired to a target MCU UART, so it has no virtual COMPORT capability.(the physical connection is missing.) you will need to add physical link wires to the Discovery board or connect to a separate USB-to-UART adaptor.
    Maybe this is your issue.

    Gyessine_0-1771165345343.png

    If this isn't your issue , please provide more informations
    BR
    Gyessine

    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.
      Andrew Neil
      Andrew Neil
      Super User
      Feb 16, 2026 10:01 AM UTC
      @Gyessine wrote:

      the ST-Link embedded in the F407 discovery is not wired to a target MCU UART, so it has no virtual COMPORT capability

      It does have the VCP (Virtual COM Port) capability in the ST-Link itself - it just lacks the physical connection from the ST-Link to the F407 Target MCU

      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.
      Andrew Neil
      Andrew Neil
      Super User
      Feb 16, 2026 10:46 AM UTC

      Welcome to the forum.

      As @gbm says, it helps to give more details about your situation - see:

      How to write your question to maximize your chances to find a solution

       

      @avatar_ang wrote:

       it didn't work when the tutorial I'm following worked for him

      Was that tutorial specifically for the STM32F407G-DISC1 board?

      Please also post a link to that tutorial.

       

      What "serial monitor" are you using?

      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.
      avatar_angAuthor
      Associate
      Feb 23, 2026 3:10 PM UTC

      thanks for mentioning the USB to UART converter we used one and it worked

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