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Associate
August 22, 2026
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STM32H743 and STM32H745 Embedded Bootloader Version Upgrade - V9.1 to V9.2

  • August 22, 2026
  • 2 replies
  • 40 views

We are using STM32H743 and STM32H745 in our product lines and embedded bootloader is used for boot loading. The PB14 pins is used as Debug Uart on USART1. 

The PA9 pin is left unconnected. Its Not Connected pin. Is there any impact on this upgrade. 

The ST Application notes says that in V9.2, the same data output issue on V9.1 is fixed. Since PA9 is not used in schematics, there is no impact on this upgrade. This is my preliminary assessment. Anybody please confirm if my understating is correct. 

Thanks in advance

 

Best answer by mƎALLEm

Hello  @shine_1  and welcome to the ST community,


@shine_1  wrote:

Is there any impact on this upgrade. 


I didn't understand what do you mean by "impact on the upgrade".

Do you mean an impact on the ST bootloader behavior if PB14 is used as USART1 Debug in your application?

If yes. There is no impact. PB14 is USART1_TX. Nothing special on the application debug side. Regarding PA9 (USART1_Tx)  kept floating and if you don't have any UART activity on PA10 (USART1_Rx), you don't expect to have any problem. 

2 replies

shine_1Author
Associate
August 22, 2026

Thankyou  @mƎALLEm  . The impact I meant is on the application software/product functionality, when migrating to V9.2 bootloader. From the reply, I understand that, as PA9 is kept floating and no activity on PA10(USART1_Rx),there is no impact on application software/product functionality. Thankyou Again.

mƎALLEm
mƎALLEmBest answer
ST Technical Moderator
August 27, 2026

Hello  @shine_1  and welcome to the ST community,


@shine_1  wrote:

Is there any impact on this upgrade. 


I didn't understand what do you mean by "impact on the upgrade".

Do you mean an impact on the ST bootloader behavior if PB14 is used as USART1 Debug in your application?

If yes. There is no impact. PB14 is USART1_TX. Nothing special on the application debug side. Regarding PA9 (USART1_Tx)  kept floating and if you don't have any UART activity on PA10 (USART1_Rx), you don't expect to have any problem. 

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