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Mahdouch
Graduate II
February 14, 2025
Solved

No Output on PuTTY – STWINBX1 USART3 via ST-LINK V3MINI (COM3)

  • February 14, 2025
  • 1 reply
  • 3077 views

Hi everyone,

I'm working with an STWINBX1 board and using ST-LINK V3MINI for debugging and serial communication. However, I can't see any output on PuTTY (COM3 @ 115200 baud), even though everything seems correctly configured.

Setup Details:

  • Board: STWINBX1
  • Connection: ST-LINK V3MINI (COM3 appears in Device Manager as "STMicroelectronics STLINK Virtual COM Port")
  • USART Configuration:
    • USART3 enabled by default
    • TX/RX mapped to correct GPIOs (PB10/PB11 or PD8/PD9)
    • Baud Rate: 115200
    • Data Bits: 8, Stop Bits: 1, Parity: None, Flow Control: None
  • Tools Used:
    • STM32CubeIDE for debugging (flashes successfully)
    • STM32CubeProgrammer (UART connection to COM3 fails)
    • PuTTY (No output when running code)

What I Tried So Far:

:white_heavy_check_mark: Checked and confirmed USART3 is initialized in main.c
:white_heavy_check_mark: Added debug messages via HAL_UART_Transmit(&huart3, ...)
:white_heavy_check_mark: Toggled an LED before sending UART data (LED toggles, so the function executes)
:white_heavy_check_mark: Checked in STM32CubeMX that USART3 is mapped to the correct GPIOs
:white_heavy_check_mark: Verified ST-LINK V3MINI appears as COM3 in Device Manager
:white_heavy_check_mark: Tried enabling/disabling "VCP UART" in STM32CubeProgrammer
:white_heavy_check_mark: Tested different baud rates in PuTTY

Issue:

  • No data appears on PuTTY (COM3)
  • STM32CubeProgrammer UART mode cannot connect ("Error: Activating device: KO, verify boot mode and serial settings")

Questions:

  1. Does ST-LINK V3MINI actually support forwarding USART3 to the PC?
  2. Is there a known issue with STWINBX1 and ST-LINK VCP (Virtual COM Port)?
  3. Should I use USART1 instead of USART3, or does ST-LINK only work with specific USARTs?
  4. Do I need to configure Hardware Flow Control (RS232)?

Any help would be greatly appreciated!

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

    As I might have mentioned, I am not really versed CubeIDE.
    Although the screenshots seem to indicate the serial link is correct so far.
    You would have to check is that PD5 and PD6 are not connected to other external circuitry that prohibit usage as UART. A good ("bad") example are some Discovery boards with LCD or external memory, where the external bus interface consumes most of the peripheral connections & options.
    Looking it up, ST's website says :
    > For wired connectivity, it includes a USB Type-C® port that can be used for power supply, data transfer and STM32 programming via DFU, and an RS-485 transceiver. 

    This is a relatively broad statement, I would check the user manual about details.
    RS-485 is very similiar to "normal" RS-232, but not compatible on electrical level.


    I would first check what works, and what doesn't.
    Flash an application that transmits regularly via UART2, and then check the UART signals (Tx) near the target MCU, at the debug connector, and finally at the ST-LinkV3 (Rx). A scope would be optimal, but a logic analyser works, too.
    If the STWinbx1 board has a MCU reset button, you don't even need to fire up the CubeIDE debugger. Just connect the probe, and press rest. You should see at least UART signals on the UART2.Tx pin of the target MCU.

    1 reply

    A
    Andrew Neil
    Super User
    February 14, 2025
    @Mahdouch wrote:

    2. Should I use USART1 instead of USART3, or does ST-LINK only work with specific USARTs?

    The ST-Link neither knows nor cares what UART you use - all it does is send data out of its 'send' pin, and all it sees is data arriving at its 'receive' pin. It doesn't even know that you're using an STM32 at all!

    Start by doing a basic application which just transmits from the UART - nothing else - to prove basic connectivity.

    https://wiki.st.com/stm32mcu/wiki/Getting_started_with_UART

    https://wiki.st.com/stm32mcu/wiki/STM32StepByStep:Step3_Introduction_to_the_UART

    https://community.st.com/t5/stm32-mcus/implementing-uart-receive-and-transmit-functions-on-an-stm32/ta-p/694926 

     

    Some tips on debugging serial comms:

    https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/tac-p/706966/highlight/true#M49

      M
      MahdouchAuthor
      Graduate II
      February 14, 2025

      Hello @Andrew Neil 

      Thanks for the links and suggestions! I’m having a look at them now and will explore the resources provided. I’ll keep you updated on my progress.

      Best regards,
      Mahdouch

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