STM32H7 - Write float value into flash memory permanently

[yaxsomo]

Hello Everyone,

I'm trying to write a float value into my STM32H743VIT6 flash memory, bit it jumps straight to the HardFaultHandler and I cannot understand why...

Here's the two functions:  

HAL_StatusTypeDef Store_AltitudeMax(float altitude)
{
    HAL_StatusTypeDef status;
    uint32_t FirstSector, NbOfSectors, SectorError;
    FLASH_EraseInitTypeDef EraseInitStruct;

    // Ensure data is written in a full 32-byte Flash word
    uint64_t FlashWord[4] = { 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF,
                              0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF };

    memcpy(&FlashWord[0], &altitude, sizeof(float));

    // Unlock Flash
    status = HAL_FLASH_Unlock();
    if (status != HAL_OK)
    {
        return status;
    }

    // Get the sector of ALTITUDE_MAX_ADDRESS
    FirstSector = GetSector(ALTITUDE_MAX_ADDRESS);
    NbOfSectors = 1;  // Only erase 1 sector

    // Configure Erase Structure
    EraseInitStruct.TypeErase     = FLASH_TYPEERASE_SECTORS;
    EraseInitStruct.VoltageRange  = VOLTAGE_RANGE;
    EraseInitStruct.Banks         = FLASH_BANK;
    EraseInitStruct.Sector        = FirstSector;
    EraseInitStruct.NbSectors     = NbOfSectors;

    // Erase Flash Sector
    if (HAL_FLASHEx_Erase(&EraseInitStruct, &SectorError) != HAL_OK)
    {
        HAL_FLASH_Lock();
        return HAL_ERROR;
    }

    // Program the Flash word (32 bytes)
    status = HAL_FLASH_Program(FLASH_TYPEPROGRAM_FLASHWORD, ALTITUDE_MAX_ADDRESS, (uint32_t)FlashWord);

    // Lock Flash after programming
    HAL_FLASH_Lock();
    return status;
}

float Retrieve_AltitudeMax(void)
{
    float altitude = 0.0f;
    uint64_t FlashWord[4];

    // Read from Flash (direct memory access)
    memcpy(FlashWord, (uint64_t*)ALTITUDE_MAX_ADDRESS, sizeof(FlashWord));

    // Extract stored float value
    memcpy(&altitude, &FlashWord[0], sizeof(float));

    return altitude;
}

And the test snippet : 

  HAL_StatusTypeDef ret = Store_AltitudeMax(768);

  if(ret != HAL_OK) {
	  printf("Something went wrong with the storage of the variable! \r\n");
  } else {
	  HAL_Delay(3000);

	  float value = Retrieve_AltitudeMax();

	  printf("Altitude retrieved: %d \r\n", (int)value);
  }

Can anyone tell me what's going on here ?

[TDK]

What is the value of ALTITUDE_MAX_ADDRESS? It needs to be 256-bit aligned.

Step through the code, which line does it go to a hard fault?

/**
  * @brief  Program a flash word at a specified address
  * @PAram  TypeProgram Indicate the way to program at a specified address.
  *         This parameter can be a value of @ref FLASH_Type_Program
  * @PAram  FlashAddress specifies the address to be programmed.
  *         This parameter shall be aligned to the Flash word:
  *          - 256 bits for STM32H74x/5X devices (8x 32bits words)
  *          - 128 bits for STM32H7Ax/BX devices (4x 32bits words)
  *          - 256 bits for STM32H72x/3X devices (8x 32bits words)
  * @PAram  DataAddress specifies the address of data to be programmed.
  *         This parameter shall be 32-bit aligned
  *
  * @retval HAL_StatusTypeDef HAL Status
  */
HAL_StatusTypeDef HAL_FLASH_Program(uint32_t TypeProgram, uint32_t FlashAddress, uint32_t DataAddress)

[yaxsomo]

Hello TDK,

Finally I found the solution.

Actually, the Both functions seems good.

the 3 defines that i created during the issue were the following : 

#define ALTITUDE_MAX_ADDRESS  0x081E0000U 
#define FLASH_BANK            FLASH_BANK_1
#define VOLTAGE_RANGE         FLASH_VOLTAGE_RANGE_3

The HardFaultHandler issue occurred during the Retrieve_AltitudeMax function.

I just changed the FLASH_BANK value to FLASH_BANK_2 and it solved the issue. Can you tell me if the two functions are optimized or if i can do better? 

Maybe it's not a smart question, but why this change solved the issue ? And why on this particular H7 model, there's not really explicit informations on the flash addresses on the datasheet? Does this apply on all H7 MCUs?

[TDK]

The reference manual is the best source of information. It will have the memory map and flash layout. The datasheet is secondary.

STM32H742, STM32H743/753 and STM32H750 Value line advanced Arm®-based 32-bit MCUs - Reference manual