A solution to resolve and exit from the BusFault triggered by am Flash memory double-fault ECC

I have spent a bit of time looking for a solution on how-to deal with BusFault caused by a flash-read ECC event. This is what I would like to share with others in the absence of finding an online solution myself.

void fv_flash_eec_test(void)

{

   volatile uint8_t      u8_i;

   volatile uint32_t      u32_addr, u32a_rd[8], u32a_wr[8];

   // enable BusFault interrupt to prevent escalation to a HardFault

   NVIC_SetPriority(BusFault_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(), 0, 0));

   NVIC_EnableIRQ(BusFault_IRQn);

   // enable interrupt

   LL_HANDLER_EnableFault(LL_HANDLER_FAULT_BUS);

   u32_addr         = ADDR_FLASH_SECTOR_4_BANK1;

   fu8_flash_erase_sector(FLASH_SECTOR_4, 1);

   // no fault triggered

   for (u8_i = 0; u8_i < 8; u8_i++)

   {

      u32a_rd[u8_i]         = *(volatile uint32_t *) (u32_addr + (sizeof(uint32_t) * u8_i));

   }

   memset(&u32a_wr[0], 0x23, sizeof(uint32_t) * 8);

   HAL_FLASHEx_Unlock_Bank1();

   HAL_FLASH_Program(FLASH_TYPEPROGRAM_FLASHWORD, u32_addr, (uint32_t) &u32a_wr[0]);

   HAL_FLASHEx_Lock_Bank1();

   // no fault triggered

   for (u8_i = 0; u8_i < 8; u8_i++)

   {

      u32a_rd[u8_i]         = *(volatile uint32_t *) (u32_addr + (sizeof(uint32_t) * u8_i));

   }

   // corrupt a 32bit segment

   u32a_wr[3]         = 0xD4;

   HAL_FLASHEx_Unlock_Bank1();

   HAL_FLASH_Program(FLASH_TYPEPROGRAM_FLASHWORD, u32_addr, (uint32_t) &u32a_wr[0]);

   HAL_FLASHEx_Lock_Bank1();

   // this will trigger a BusFault

   for (u8_i = 0; u8_i < 8; u8_i++)

   {

      u32a_rd[u8_i]         = *(volatile uint32_t *) (u32_addr + (sizeof(uint32_t) * u8_i));

   }

   while (1) {}

}

/**

 * @brief This function handles Pre-fetch fault, memory access fault.

 */

void BusFault_Handler(void)

{

   // check for a double ecc fault

   if (FLASH->SR1 & FLASH_SR_DBECCERR)

   {

      // clear flag

      FLASH->CCR1      |= FLASH_CCR_CLR_DBECCERR;

      // flash programming is done in block of 256-bits (8 x uint32)

      uint32_t   u32_addr = SCB->BFAR;

      uint32_t   u32a_wr[8] = {0};

      // place on a 256-bit boundary

      u32_addr         = (u32_addr >> 5) << 5;

      // overwrite all data to zero - this will remove the ecc fault and clear the interrupt

      HAL_FLASHEx_Unlock_Bank1();

      HAL_FLASH_Program(FLASH_TYPEPROGRAM_FLASHWORD, u32_addr, (uint32_t) &u32a_wr[0]);

      HAL_FLASHEx_Lock_Bank1();

   }

   // clear any pending interrupts

   NVIC_ClearPendingIRQ(BusFault_IRQn);

}