Wrong flash size for eeprom emulation

[JyeSmith]

Hey,

I am trying to use eeprom on the STM32L432. It should be pretty straight forward but I dont appear to be having any luck. Is someone able to confirm it works?

Cheers

[fpistm]

Hi @JyeSmith
could you be more precise ?
Which board? Arduino IDE version? Core version ?
Which sketch?

Basically the EEPROM library is an emulation using last page flash.

[fpistm]

I've tested eeprom_put and eeprom_get default examples and it works fine on the Nucleo L432KC

[cruwaller]

@fpistm this is not working as expected on L432 when flash size is smaller than max 256kB :)

We have used stm32l432kbu6 which has 128kB of FLASH.

Current code calculates flash page index:
#define FLASH_PAGE_NUMBER ((uint32_t)((FLASH_SIZE / FLASH_PAGE_SIZE) - 1))
=> FLASH_SIZE returns 0x20000 and page is 0x800 => page 63 (the address 0x0801F800).

Then EEPROM base address is defined:
#define FLASH_BASE_ADDRESS ((uint32_t)((FLASH_END + 1) - FLASH_PAGE_SIZE))
=> #define FLASH_END (0x0803FFFFUL) is defined in stm32l432xx.h => 0x0803FFFFUL => base address will be 0x803F800 which is actually page 127 :)

This means that EEPROM save will work just once after mass erase because wrong flash page is erased :)
This means that EEPROM will write data out of bounds :)

Could you reopen this error?

[fpistm]

@ABOSTM could you have a look on this please? Thanks in advance.

[ABOSTM]

@JyeSmith,
I agree with you, it is a real issue.
FLASH_END which is defined in CMSIS file doesn't take into account the real flash size of a the device,
(it is just the maximum possible within the productline).

But fix will be a real challenge, as other STM32 series are impacted, and it will be difficult to find generic implementation, taking into account single bank/dual bank, possible flash discontinuity between banks, ...
So as a workaround, I propose you to update, for now, stm32l432xx.h with the value you expected:
#define FLASH_END (0x0801FFFFUL)