TSDHD STM32H7S7I8T6

[Y007]

Hello ST Community,

I am using TSD HD Gen4-STM32-43CT-01 display module which has STM32H7S7I8T6 MCU.
I am facing an issue where I am unable to connect or disconnect the debugger using MB1440C, while the same debugger works perfectly with other TSD HD Gen4 displays.

Debugger setup

• Debugger: MB1440C

• Interface: SWD

• Connections:

  • SWDIO → JTMS

  • SWCLK → JCLK

  • GND → GND

This setup was working earlier on the same board.

What changed

The last firmware flashed was a boot-level application intended to write custom data into external QSPI flash:

• External Flash: GD25Q127CS (128 Mbit)

After flashing this boot code:

• The MCU is no longer connectable via SWD

• ST-LINK / MB1440C cannot attach

• Power cycling does not help

Observations

• Same MB1440C debugger + same CubeIDE works fine with other TSD HD displays

• Issue is specific to this board after boot code flashing

• I suspect:

  • SWD pins may be reconfigured as GPIO

  • Option Bytes may have been modified

  • Boot code may be disabling debug or putting MCU in low-power/reset loop

  • External QSPI initialization may be locking the system early

I would appreciate any guidance on hardware recovery steps, forced boot modes, or debugger connection techniques specific to STM32H7S7.

Thank you in advance.