Dear ST staff, I am using the nucleo board STM32L476RG to flash a STM32L476ZGT6. I once wrongly connected the SWD pins. I am now only able to erase the microcontroller flash: I cannot flash the microcontroller again. Do you have a clue?

[PFavr.1]

Note:The hardware is still functional, I made sure of it.

[waclawek.jan]

Can you connect to the target e.g. in STLink Utility?

JW

[PFavr.1]

Hello Jan,

Thanks for your feedback.

I could connect to the target via ST Link:

11:09:56 : Connected via SWD.

11:09:56 : SWD Frequency = 4,0 MHz.

11:09:56 : Connection mode : Connect Under Reset.

11:09:56 : Debug in Low Power mode enabled

PF

[Ozone]

Most people here are not ST staff.

> I could connect to the target via ST Link:

And what are the error messages when you try to flash ?

[PFavr.1]

Hello,

The problem came from specific backup registers that needed to be reset.

You can find below the SW excerpt related to the needed action:

HAL_Init(); 

HAL_DBGMCU_EnableDBGStandbyMode();

__HAL_RCC_BACKUPRESET_FORCE();

__HAL_RCC_BACKUPRESET_RELEASE();

Thank you all for your help,

PF

[Tesla DeLorean]

Strap the BOOT0 pin HIGH, connect, do a mass erase, and set option bytes to defaults.​