How to use Backup SRAM as EEPROM in STM32F4

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There are two ways of emulating EEPROM on the STM32F4:

  1. On-chip 4 Kbytes backup SRAM
  2. On-chip Flash, with specific software algorithm

The second option is described here: AN3969.

But google, unfortunately, hasn't been able to provide information on how to use the first option - using the 4Kb of backup SRAM as EEPROM?..

Can anyone help on the topic?

eeprom stm32f4discovery stm32
7 Answers

Here is the example of HAL library to use backup SRAM.

#define  WRITE_READ_ADDR  0x01 //offset value.you can change according to your application
uint32_t write_arr = 0xA5A5A5A6;
uint32_t read_arr;

int main()
{
   enable_backup_sram();
   writeBkpSram(write_arr);
   while(1)
   {
      read_arr = readBkpSram();
   }
}
void enable_backup_sram(void)
{
    /*DBP : Enable access to Backup domain */
    HAL_PWR_EnableBkUpAccess();
    /*PWREN : Enable backup domain access  */
    __HAL_RCC_PWR_CLK_ENABLE();
    /*BRE : Enable backup regulator
      BRR : Wait for backup regulator to stabilize */
    HAL_PWREx_EnableBkUpReg();
   /*DBP : Disable access to Backup domain */
    HAL_PWR_DisableBkUpAccess();
}

void writeBkpSram(uint32_t l_data)
{
   /* Enable clock to BKPSRAM */
  __HAL_RCC_BKPSRAM_CLK_ENABLE();
  /* Pointer write on specific location of backup SRAM */
  (uint32_t *) (BKPSRAM_BASE + WRITE_READ_ADDR) = l_data;
 /* Disable clock to BKPSRAM */
 __HAL_RCC_BKPSRAM_CLK_DISABLE();
}

uint32_t readBkpSram(void)
{
   uint32_t i_retval;

  /* Enable clock to BKPSRAM */
  __HAL_RCC_BKPSRAM_CLK_ENABLE();
  /* Pointer write from specific location of backup SRAM */
  i_retval =  *(uint32_t*) (BKPSRAM_BASE + WRITE_READ_ADDR);
  /* Disable clock to BKPSRAM */
  __HAL_RCC_BKPSRAM_CLK_DISABLE();
  return i_retval;
}
user_57463510

HAL Configuration for STM32H7 to access backup SRAM:

#define BKP_RAM (*(__IO uint32_t *) (D3_BKPSRAM_BASE)) //Start address: 0x38800000

Main() {

__HAL_RCC_BKPRAM_CLK_ENABLE();

HAL_PWREx_EnableBkUpReg();

BKP_RAM = 0xA5AA5A55;

}

In addition to that, you need to add a below line in systemInit() to enable write-through access to Backup SRAM.

SCB->CACR |= 1<<2;
user_84112170
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