STM32H747IIT6 CM4 not responding

aradhyab · ‎2026-02-05

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

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.

mƎALLEm · ‎2026-02-05

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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aradhyab · ‎2026-02-06

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 · ‎2026-02-06

@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:

BCM4 should be checked as shown in the screenshot.

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aradhyab · ‎2026-02-08

Yes, I undefined dual boot core sequence at both the sides and BCM4 is also checked as shown by your screenshot.

aradhyab · ‎2026-02-13

Hello @mƎALLEm

Can you provide me any other way to boot CM4 again. I am unable to do it yet. I was in debug mode and restarted the controller when CM4 stopped responding. Even after erasing the codes in both the cores, CM4 is still not responding.

mƎALLEm · ‎2026-02-13

Hello,

Check also if CM4 boot addresses have the following values in the option bytes:

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aradhyab · ‎2026-02-17

Hello,

I checked the addresses, they are correct.

Is there anything else that needs to be checked?

mƎALLEm · ‎2026-02-17

1- What board are you using?

2- Share your project

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aradhyab · ‎2026-02-19

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.