Set the bor threshold for stm32u575

[杜明恢]

  When I was developing the stm32u575, I needed to set the threshold for the bor (power-on reset). I wanted the device to reset when the voltage was below a certain level. While configuring the bor threshold for the stm32u575, I followed the configuration process of the stm32f405, but it didn't work. The program got stuck at HAL_FLASH_OB_Unlock(). Why did this happen? What was the problem?

	FLASH_OBProgramInitTypeDef OBInit;
	HAL_FLASHEx_OBGetConfig(&OBInit);

	OBInit.USERType = OB_USER_BOR_LEV;
	OBInit.USERConfig = OB_BOR_LEVEL_1;
	HAL_FLASH_OB_Unlock();
	HAL_FLASHEx_OBProgram(&OBInit);
	HAL_FLASH_OB_Launch();
	HAL_FLASH_OB_Lock();

 

[Saket_Om]

Hello ​@杜明恢 

Could you please check the return value of HAL_FLASH_OB_Unlock() first?
It would be useful to update the code so that every HAL function return status is verified.

On STM32U575, the option-byte programming flow is not identical to STM32F405, so reusing the same sequence may lead to issues. If the code appears to stop at HAL_FLASH_OB_Unlock(), the first thing to confirm is whether the function is actually returning HAL_OK, or whether it is returning an error.

[杜明恢]

The function prototype is as follows. When the program executed WRITE_REG(FLASH->OPTKEYR, FLASH_OPTKEY1), HardFault_Handler interrupt was triggered.At this moment, R13(SP) = 0x200BFF40, R14(LR) = 0xFFFFFFA8, R15(PC) = 0x08008250。I have identified the cause. The ICACHE needs to be disabled.

HAL_StatusTypeDef HAL_FLASH_OB_Unlock(void)
{
  if (READ_BIT(FLASH->NSCR, FLASH_NSCR_OPTLOCK) != 0U)
  {
    /* Authorizes the Option Byte register programming */
    WRITE_REG(FLASH->OPTKEYR, FLASH_OPTKEY1);
    WRITE_REG(FLASH->OPTKEYR, FLASH_OPTKEY2);

    /* Verify that the Option Bytes are unlocked */
    if (READ_BIT(FLASH->NSCR, FLASH_NSCR_OPTLOCK) != 0U)
    {
      return HAL_ERROR;
    }
  }

  return HAL_OK;
}

 

[Gyessine]

Hello ​@杜明恢 
Add to what ​@Saket_Om said, I should mention that you can modify BOR level using STM32CubeProgrammer
just connect the product and select the wanted BOR level
looks like an easier way

BR
Gyessine