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EliazLB
Associate III
April 8, 2025
Solved

bootloader for STM32G474QET6 - usable UART pins?

  • April 8, 2025
  • 5 replies
  • 2631 views

I am trying to use the bootloader of the STM32G474QET6 with USART to program my microcontroller. 

I have multiple questions regarding this but the first one is more about hardware. I have found in AN2606 that for the bootloader I can only use one of three USART, as listed under :

EliazLB_0-1744100551282.png

So after this info, I can use either USART1, 2 or 3 but when I look at the pins attached and at the datasheet of my microcontroller, pins for USART3 on the MCU are not PC11 and PC10. 

EliazLB_1-1744100662917.png

The thing is on my PCB I've decided to use PB10 and PB11, and according to the datasheet, they are the pins of USART3.

So my question is pretty simple, which document is right and which should I follow ? Am I going to need to change anything ? 

Thanks for the answers !

Best answer by Mike_ST

Hello,

>> pins for USART3 on the MCU are not PC11 and PC10

 

Mike_ST_0-1744102086837.png

 

>> So my question is pretty simple, which document is right and which should I follow ?

Both are right,

>> Am I going to need to change anything

If you want to use the bootloader on USART3, probably you'll need to switch to PC10/PC11.

5 replies

Andrew Neil
Andrew Neil
Super User
April 8, 2025
@EliazLB wrote:

EliazLB_0-1744100551282.png

So after this info, I can use either USART1, 2 or 3 but when I look at the pins attached and at the datasheet of my microcontroller, pins for USART3 on the MCU are not PC11 and PC10.  !

I think what it's telling you is that you can use USART1 on PA9,10; or USART2 on PA2,3; or USART3 on PC10,11.

If your particular chip does not provide those specific pins, then you can't use it on that chip.

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
April 8, 2025

Hang on!

 

@EliazLB wrote:

but when I look at the pins attached and at the datasheet of my microcontroller, pins for USART3 on the MCU are not PC11 and PC10.  !

Yes, they are:

AndrewNeil_0-1744102282872.png

 

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.
    E
    EliazLBAuthor
    Associate III
    April 8, 2025

    Yes thank you apparently I can't really read...

    Mike_ST
    Mike_STAnswer
    Technical Moderator
    April 8, 2025

    Hello,

    >> pins for USART3 on the MCU are not PC11 and PC10

     

    Mike_ST_0-1744102086837.png

     

    >> So my question is pretty simple, which document is right and which should I follow ?

    Both are right,

    >> Am I going to need to change anything

    If you want to use the bootloader on USART3, probably you'll need to switch to PC10/PC11.

      E
      EliazLBAuthor
      Associate III
      April 8, 2025

      So the simple answer is I need to use pins indicated in AN2606 ?

       

        Andrew Neil
        Andrew Neil
        Super User
        April 8, 2025

        Correct - that's why it specifically states them.

        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.
          E
          EliazLBAuthor
          Associate III
          April 8, 2025

          Alright perfect then, thank you very much !

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