STM32 FLASH Write Protection Error

[Jouls]

Hi there!
I was trying to emulate eeprom using flash memory. I am using Nucleo-F030R8 board. I was able to program flash 2 times (0xF055 was the test value):

however I cannot reproduce it anymore and whilst trying to program I get PGERR.
Uploading my code below

main.c
//while() loop - event triggered on the button press

uint8_t data[2] = {0x02 , 0x55};
if(ee_write(0, 1, (uint8_t*)data) == true)
  //success
else
  //fail

 I'm using flash page 60, starting from address 0x0800F000 (_EE_ADDR_INUSE )

bool ee_write(uint32_t startVirtualAddress, uint32_t len, uint8_t *data) {
  if ((startVirtualAddress + len) > _EE_SIZE)
    return false;
  if (data == NULL)
    return false;

  HAL_FLASH_Unlock();

  if(*(__IO uint16_t*)_EE_ADDR_INUSE != 0xFFFF){
    FLASH_PageErase(startVirtualAddress + _EE_ADDR_INUSE);
    FLASH->CR &= ~FLASH_CR_PER;
  }

#ifdef FLASH_TYPEPROGRAM_HALFWORD
  for (uint32_t i = 0; i < len ; i+=2) {
    if (HAL_FLASH_Program(FLASH_TYPEPROGRAM_HALFWORD, ((i + startVirtualAddress)) + _EE_ADDR_INUSE, (uint64_t)(data[i] | (data[i+1] << 8))) != HAL_OK)
    {
      HAL_FLASH_Lock();
      return false;
    }
  }
#endif
  HAL_FLASH_Lock();
  return true;
}

 And the error occurs while trying to execute last line of code in that function

static void FLASH_Program_HalfWord(uint32_t Address, uint16_t Data)
{
/* Clean the error context */
pFlash.ErrorCode = HAL_FLASH_ERROR_NONE;

/* Proceed to program the new data */
SET_BIT(FLASH->CR, FLASH_CR_PG);

/* Write data in the address */
*(__IO uint16_t*)Address = Data;
}

 What am I missing?

[Bob S]

I've never used the F0 series, but in general you can't write to any FLASH location more than once without erasing the entire sector of FLASH in between writes.

[Florian LR · Accepted solution]

Hi @Jouls, and welcome to the STCommunity !
You are trying to write again at the same address, and @Bob S is right about the fact you can't overwrite an existing value in the flash.

You can fin the explanation in the Reference Manual :
The flash memory interface preliminarily reads the value at the addressed main flash
memory location and checks that it has been erased. If not, the program operation is
skipped and a warning is issued by the PGERR bit in FLASH_SR register.

You can either write to a new location, or erase the current sector of the flash using the HAL function : 

FLASH_PageErase(PageAddress) (you can find this function in the file stm32f0xx_hal_flash_ex.c).

I hope this will help you !

BR, 

Florian LR

[Jouls]

You were right! Thank you all for help.
I edited the post so that one can use is in the future.