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Associate
February 6, 2026
Question

STM32H747IIT6 CM4 not responding

  • February 6, 2026
  • 2 replies
  • 416 views

I am working on STM32h747 series. I am debugging both CM4 and CM7. After a while, CM4 stops responding and the debug messages shows:

"Error in final launch sequence:

 

Failed to start GDB server

Failed to start GDB server

Error in initializing ST-LINK device.

Reason: (4) No device found on target."

 

If I run CM7 independently, it works but CM4 is not responding. I tried to erase the entire board but CM4 is still not responding and the same message is appearing.

2 replies

mƎALLEm
Technical Moderator
February 6, 2026

Hello @aradhyab and welcome to the ST community,

If you have generated the code based on CubeMx or used one of the HAL examples, CM4 enters into a low power mode state and the debug is a bit tricky. 

Do you have this definition in both mains (CM7 and CM4)?

#define DUAL_CORE_BOOT_SYNC_SEQUENCE

If yes undefine it.

Check also if CM4 is disabled in the option byte.

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aradhyabAuthor
Associate
February 6, 2026

Hello @mƎALLEm 

Thank you for the prompt response. 

Regarding

#define DUAL_CORE_BOOT_SYNC_SEQUENCE

I have undefined it but it still does not work. It shows the same error.

Can you please guide me on how to check if the option byte is enabled or disabled?

mƎALLEm
Technical Moderator
February 6, 2026

@aradhyab wrote:

Regarding

#define DUAL_CORE_BOOT_SYNC_SEQUENCE

 

 Did you undefine it at both sides CM7 and CM4?

 


@aradhyab wrote:

Can you please guide me on how to check if the option byte is enabled or disabled?


Using the STM32CubeProgrammer:
mALLEm_0-1770369381766.png

BCM4 should be checked as shown in the screenshot.

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mƎALLEm
Technical Moderator
February 18, 2026

1- What board are you using?

2- Share your project

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aradhyabAuthor
Associate
February 20, 2026

Hi,

I am using board STM32H747IIT6.

I tried a few things and it turns out that when I assign LSE clock to RTC, CM4 does not boot, but when I assign LSE to LSI, it boots. 

My requirement is to use internal clock for RTC. Can you suggest what can I do?

Also, can you tell me on where can I share my project with you? 

 
 

I have also attached the clock configuration images for your reference. The first image is the configuration which is not working and the second one seems to work. 

 

mƎALLEm
Technical Moderator
February 20, 2026

Hello,


@aradhyab wrote:

I am using board STM32H747IIT6.


That's the chip not the board. Are you using a ST board: Eval board? discovery board? or a custom board?

 


@aradhyab wrote:

it turns out that when I assign LSE clock to RTC, CM4 does not boot, but when I assign LSE to LSI, it boots. . 


Sorry not clear. what do you mean assign LSE to LSI? do you mean if the RTC clock source is LSE CM4 doesn't boot while if the RTC clock source is LSI CM4 does?

And I've already requested to attach your project. I cannot help you with the elements you've provided.

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