Hi,
I've flashed an application in the STM32N6570-DK board using a FSBL and Appli projects. The application boots fine.
But when the application is running, I can't attach to it using the debugger and ST-Link.
I've tried to open the debug port of the STM32N6 by writing 0xB4 to the BSEC_AP_UNLOCK register, but it still fails.
The error I get is:
STMicroelectronics ST-LINK GDB server. Version 7.11.0
Copyright (c) 2025, STMicroelectronics. All rights reserved.
Starting server with the following options:
Persistent Mode : Disabled
Logging Level : 1
Listen Port Number : 61234
Status Refresh Delay : 15s
Verbose Mode : Disabled
SWD Debug : Enabled
Target unknown error 32
Error in initializing ST-LINK device.
Reason: Unknown. Please check power and cabling to target.Using STM32CubeProgrammer, I get this error on Access Port 1 with Hot Plug mode:
But I've not configured anything: I've not blown any OTP fuse, nor changed any Option bytes. And I'm not using a secure bootloader, I have just the generated FSBL from STM32CubeMX which loads the application from flash to RAM using ExtMemManager.
I'm assuming the DEV_MODE is doing something to open the debug access before doing it's busy loop waiting for a debugger to attach.
As a workaround, I can get the debugger to work if I do this:
- Switch to DEV_MODE
- Power-up the board
- Switch to FLASH boot mode without power-cycling
- Press the reset button
Then the application will start from flash and I can attach the debugger.
How to open the debug access from the application even without using DEV_MODE ?
