Programming user option bytes

[fabien]

Posted on October 15, 2014 at 14:52

Hello,

I would like to know if it is possible to change the value of the register FLASH_OPTCR by mapping a variable on it and to set the value in constant ? I think this is not possible because we need to respect a predefined sequence to unlock the register but I can always ask for the question :) Example of what I want :

const u32 u32_FlashOptcr @ 0x40023C14 = 0xFFFFFFFF;

Thanks, Fabien.

[chen]

Posted on October 15, 2014 at 15:12

Hi

''I would like to know if it is possible to change the value of the register FLASH_OPTCR by mapping a variable on it and to set the value in constant ? I think this is not possible because we need to respect a predefined sequence to unlock the register''

You are correct - you cannot just load it with a single constant value.

There are APIs for doing this in the peripheral library :

stm32f4xx_flash.c

FLASH_OB_Unlock()

FLASH_OB_WRPConfig()

FLASH_OB_Lock()

[fabien]

Posted on October 15, 2014 at 15:22

Thanks for the response.

I know about the APIs, but the purpose of my idea was to protect the flash by just flashing a software, and to not make other manipulation with other sofwtare like ''STM32 ST-LINK Utility'' to change the option bytes.

[chen]

Posted on October 15, 2014 at 15:35

''the purpose of my idea was to protect the flash by just flashing a software, and to not make other manipulation with other sofwtare like ''STM32 ST-LINK Utility'' to change the option bytes.''

I do not understand - maybe it is your english.

The ST-Link will automatically un-lock any write protected sectors and re-lock them afterwards.

So the ST-Link can over-ride the write protect bits anyway!

[Tesla DeLorean]

Posted on October 15, 2014 at 16:48

The options and flash can be programmed by user code, you don't have to use ST-LINK Utilities, or external tools/interfaces, to achieve this.

[fabien]

Posted on October 15, 2014 at 16:55

Sorry for my english :(

I just see the ''Automatic Mode'' in st-link utility and I think it will do the job :)

I will try to use the st-link utility with command line to unlock flash, program and relock the flash.

Thanks.