How to use the Backup SRAM of a STM32F7 / STM32

gistfile1.txt

This might also work for other STM32 chips. I use the HAL, so it also might be supported by your chip.

To use the Backup SRAM (most of the time 4 Kb), you need to add a backup power source (like a battery or a supercap)
to the VBAT pin of your STM32. I use a simple CR2032 battery.

Use following code to get access to the Backup SRAM:

  __HAL_RCC_PWR_CLK_ENABLE();
  HAL_PWR_EnableBkUpAccess();
  __HAL_RCC_BKPSRAM_CLK_ENABLE();

After this, you can already read / write to the Backup SRAM, but to save the content in case of a power loss of the 
main power, you need to active the backup power regulator:

  // Enable backup regulator
  LL_PWR_EnableBkUpRegulator();
  // Wait until backup regulator is initialized
  while (!LL_PWR_IsActiveFlag_BRR());

Now you can safely save your content in the Backup SRAM.

You can write to it like this:

  *(__IO uint8_t *) (BKPSRAM_BASE + offset) = x;

You can read from it like this:

  uint8_t x = (*(__IO uint8_t *) (BKPSRAM_BASE + offset));

Thanks for the contribution! This works for me only in combination with DCache invalidation, refer to this STM community post