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shubhenduatadben
Associate III
December 24, 2025
Solved

STM32H7A3AII6Q Internal bootloader boot for firmware update.

  • December 24, 2025
  • 2 replies
  • 473 views

Hello,

    I'm working into writing firmware image to a STM32H7A3AII6Q via internal boot-loader. I'm using AN2606 and AN3155 as reference documents. 
    The boot-loader entry sequence I'm using:
State 1: BOOT0: high

              RST: low

State 2: Wait 200 ms

State 3: BOOT0: high

              RST: high

Then I'm sending 0x7F over USART2 but, getting no response(0x79).

Can you please help me what might be wrong here?

Best answer by mƎALLEm

Sorry I have an issue with the notifications today and didn't know you replied to me.

From your oscilloscope screenshot it seems you have that 0x7F which the target is waiting for:

mALLEm_0-1766587829852.png

Meanwhile I still insist on the hardware check:

1- Is there a mean to connect with the STM32H7 with STLINK?, to confirm if the chip is alive?

2- If you can connect with ST-LINK, check again your hardware and continuity between STM32H7_TX / USB-USART_Rx and  STM32H7_RX / USB-USART_Tx. You need to confirm that part and check if you are using the right pins. You could have a mismatch with what you are really doing and what you are thinking about what you did ;).

 

 

 

2 replies

mƎALLEm
mƎALLEm
Technical Moderator
December 24, 2025

Hello,

You didn't tell what IOs you have used for USART2? PA2 and PA3?

mALLEm_0-1766568617243.png

If yes check your wiring (continuity test). Use an oscilloscope to check what happens on Tx and Rx.

 

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S
shubhenduatadbenAuthor
Associate III
December 24, 2025

The board uses USART2: PA2,PA3. The USART is working well when connected to other boards and running application firmware. But, when isolated and tested by serial, there is no activity on USART: TX in the oscilloscope. 

The USB serial parameters:

BAUD: 115200

PARITY: EVEN

STOP: 1

mƎALLEm
mƎALLEm
Technical Moderator
December 24, 2025
@shubhenduatadben wrote:

The USB serial parameters:

BAUD: 115200

PARITY: EVEN

STOP: 1

You need to check that USB to UART bridge..connect its tx and rx and use an Hyperterminal and check if what you send you receive it. 

And use CubeProgrammer to connect to the ST bootloader: 

mALLEm_0-1766571995294.png

 

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TDK
TDK
Super User
December 24, 2025

You need to be in the bootloader in order for 0x7F to have an effect. AN2606 lists the ways to enter the bootloader. Most commonly, holding BOOT0 high during reset will enter the bootloader under most circumstances.

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