Code example - how to write 2 bytes to permanent memory.

[GS2]

Hello,

Is there code example for writing 2 bytes to the permanent memory at runtime, so it will stay there after power off?

For any STM32 or better STM32WB55.

[Andrew Neil]

https://community.st.com/t5/stm32-mcus-embedded-software/x-cube-eeprom-not-for-stm32f0/m-p/684685/highlight/true#M48486

[GS2]

Thank you,

Looks like it is possible, but too complicated!

So there is no small peace of code!

[Tesla DeLorean]

The Cube repo's should have "FLASH" examples, and "EEPROM" where appropriate.

The "Write" code can be fairly concise, usually UNLOCK, SET PROGRAM MODE, WRITE WORD[S], CHECK STATUS/COMPLETION, CLEAR MODE, LOCK

How "permanent" are we talking about? OTP?

2-bytes doesn't seem like enough for a KEY

With the FLASH, the minimum ERASE tends to be quite large, and costly in time. For small items one can journal multiple small writes over the page/sector. Write lines might impose further limits, to implement ECC in hidden bits. So 32-bit or 64-bit minimums might apply. Check part's RM

BKPRAM / NVRAM ?

[Tesla DeLorean · Accepted solution]

Small Piece? If using HAL it's likely to pull in a metric shed-ton of other clutter, but at a register level can be done relatively concisely if necessary.

https://github.com/STMicroelectronics/STM32CubeWB/blob/master/Projects/NUCLEO-WB15CC/Examples/FLASH/FLASH_EraseProgram/Src/main.c#L168

Expectations of Address alignment compatible with the flash array / write-lines

  /* Unlock the Flash to enable the flash control register access *************/
  HAL_FLASH_Unlock();

 /* Clear OPTVERR bit set on virgin samples */
  __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_OPTVERR);
   ...
    if (HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, Address, DATA_64) == HAL_OK)
     ...

  /* Lock the Flash to disable the flash control register access (recommended
     to protect the FLASH memory against possible unwanted operation) *********/
  HAL_FLASH_Lock();

[GS2]

Thank you very much. I will try to make it work.