So I was testing the boot option bytes of my Nucleo32 STM32G431KB board and somehow my Nucleo board is in Read Out Protection level 1. STLink Utility is unable to revert it, I get the error "Read/Write protected zone for bank 1 can't be reduced".

enter image description here

These are the only lines of code I had in main():

//STCubeIDE autogenerated code...
//STCubeIDE autogenerated code...

I also tried to bypass the STLink and try if I could communicate directly to IC's bootloader using a FTDI driver and writing raw bytes to UART, because there is a command to revert the ROP, but I had no reply from the chip.

  • 1
    \$\begingroup\$ The readout protection feature would be pretty pointless if you could just reduce it like that in the ST-LINK utility. You'll probably have to erase the chip to clear the protection. \$\endgroup\$
    – brhans
    Feb 18, 2021 at 13:32

1 Answer 1


I think I've managed to recover the board, using STM32CubeProgrammer (not CubeIDE, this is a different program).

The only thing I had to do was changing RDP to 0xAA (no protection) and now I can reprogram the IC.

First install the program and click Connect to STLink, then:

enter image description here

  • 4
    \$\begingroup\$ Just a warning for readers of this answer: Do not choose CC. Doing so places uC in Level 2 protection, permanently disables debug and bricks the uC. You can not recover from Level 2 protection . \$\endgroup\$
    – Tagli
    Feb 18, 2021 at 14:02

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