3 years, 8 months ago.

EEProm Emulation on STM32L432KC

Hello, my question is a bit stupid, but i have spent one week to check the forum and trying different methods how to solve it and without sucess :( I am using the Nucleo STM32L432KC and I need to save only 5 bytes into the EEPROM as a configuration data. Because this MCU don't have EEPROM it is necessary to save it into Flash. I have found few examples and I have tested it - but without success.

One, which is here in forum was to use the back-up registers from RTC, but there is necessary to have backup battery - i dont have it in my application :(

Second was to use Flash HAL API. I did a short test below, but EEdata_read on the end are 0, not 55.

uint32_t EEaddress = 0x8020000; start on 128kB

uint8_t EEdata_write = 55;

uint8_t EEdata_read;

uint32_t EEsize = 1;

int32_t flash_init (flash_t *obj);

int32_t flash_program_page(flash_t *obj, uint32_t EEaddress, const uint8_t *EEdata_write, uint32_t EEsize);

int32_t flash_read(flash_t *obj, uint32_t EEadress, uint8_t *EEdata_read, uint32_t EEsize);

The third what I tested was recommendation from this page http://micromouseusa.com/?p=606 but also without success :(

And I can continue - I really tested lot of different examples during this week, but with the same result - it is not working :(

Is here somebody who can recommend me simple and working solution how to save 5 bytes? I am realy desperate, because I am bit new in programing of ARM and I am not able to make some working solution myself :(

Thank you very much, I will be very grateful for your help.


1 Answer

3 years, 8 months ago.

Hello Lukas,

That must be very frustrating :( I haven't tried it yet but the Flash IAP might help solve the issue.
Have a look also at https://os.mbed.com/questions/82407/How-do-I-use-a-txt-file-in-an-embedded-d.

Hello, thank you very much for your fast answer. I have also tried this library, but also without success :(

address 0x8020000 means: from 128 kB

uint32_t EEaddress = 0x8020000; uint8_t EEdata_write = 55; uint8_t EEdata_read; uint32_t EEdata_size = 1; uint32_t EEsizeSector = 2048;

in program

FlashIAP(); int init();

int erase(uint32_t EEadress, uint32_t EEsizeSector); int program(const void *EEdata_write, uint32_t EEadress, uint32_t EEdata_size);

int read(void *EEdata_read, uint32_t EEadress, uint32_t EEdata_size);


And after this t_max=0 not 55 :( And I am really not sure regarding size of sectors (but in datasheet is info that this MCU has 256kB of flash in 128 x 2kbyte) and also regarding address 0x8020000..... (My program is now 59kB HEX file)

My flustration is growing :)

posted by Lukas Bier 11 Oct 2018

You made me curious about the Flash IAP. Unfortunately I have no access to a NUCLEO-L432KC. So below is a program which worked for me on a NUCLEO-F446RE.

#include "mbed.h"
FlashIAP flash;

int main() {
    const uint32_t  flash_start = flash.get_flash_start();
    const uint32_t  flash_size = flash.get_flash_size();
    const uint32_t  flash_end = flash_start + flash_size;
    const uint32_t  page_size = flash.get_page_size();
    uint32_t        sector_size = flash.get_sector_size(flash_end - 1);
    uint8_t*        page_buffer = new uint8_t[page_size];
    uint32_t        addr = flash_end - sector_size;   
    uint8_t         EEdata_write = 55;
    uint8_t         EEdata_read = 0;
    printf("flash_start = 0x%.8x\r\n", flash_start);
    printf("flash_size = 0x%.8x\r\n", flash_size);
    printf("flash_end = 0x%.8x\r\n", flash_end);
    printf("page_size = 0x%.8x\r\n", page_size);
    printf("sector_size = 0x%.8x\r\n", sector_size);
    printf("addr = 0x%.8x\r\n", addr);
    printf("EEdata_write = %d\r\n", EEdata_write);
    printf("EEdata_read = %d\r\n", EEdata_read);   
    page_buffer[0] = EEdata_write;   
    flash.erase(addr, sector_size);
    flash.program(page_buffer, addr, page_size);   
    page_buffer[0] = 0;   
    flash.read(page_buffer, addr, page_size);
    EEdata_read = page_buffer[0];   
    delete[] page_buffer;
    printf("EEdata_read = %d\r\n", EEdata_read);

ADVISE: To have a more readable code published here (on mbed pages) try to mark it up as below (with <<code>> and <</code>> tags, each on separate line at the begin and end of your code)

text of your code

posted by Zoltan Hudak 11 Oct 2018

Dear Zoltan, thank you very much for your code example. Now I can see how big idiot I am !!.... You can not imagine how much you helped me and how many nights you have saved me... Thank you once again.

posted by Lukas Bier 11 Oct 2018

Never mind, Lukas, I'm glad for being of help to solve the issue.

posted by Zoltan Hudak 11 Oct 2018