STM32F072 - How do i know what flash pages available to save data ?

Use the ones at the end of memory, and shrink the allocation reported to the linker for your code (ie menu settings, scatter file, or linker script)

To see how much memory you're using currently, review the .MAP file.

Hello Clive ,

1. thanks you for your time TO answer me ,
2. looking at the .map as you said i see few "blocks " of Rom
3. 2.1 is Image Entry point : 0x080000c1 is FLASH Region _IROM1 () just to be 100% sure ?

Image Entry point : 0x080000c1

 Load Region LR_IROM1 (Base: 0x08000000, Size: 0x0000287c, Max: 0x00020000, ABSOLUTE)

  Execution Region ER_IROM1 (Base: 0x08000000, Size: 0x00002840, Max: 0x00020000, ABSOLUTE)

  Base Addr  Size     Type  Attr   Idx  E Section Name    Object

  0x08000000  0x000000c0  Data  RO      3  RESET        startup_stm32f072xb.o

  0x080000c0  0x00000000  Code  RO     4241 * .ARM.Collect$$$$00000000 mc_p.l(entry.o)

  0x080000c0  0x00000004  Code  RO     4556  .ARM.Collect$$$$00000001 mc_p.l(entry2.o)

....

....

...

 0x08002676  0x00000002  PAD

  0x08002678  0x00000190  Code  RO     294  i.main       main.o

  0x08002808  0x00000010  Data  RO     4201  .constdata     system_stm32f0xx.o

  0x08002818  0x00000008  Data  RO     4202  .constdata     system_stm32f0xx.o

  0x08002820  0x00000020  Data  RO     4611  Region$$Table    anon$$obj.o

so from  0x00000021 for this program all FLASH above should be free for my own data to write ro flash use ?

thanks

Check the flash memory section in the reference manual.

Additionally you can use STM32 ST-LINK UTILITY software to view the memory address you have accessed/used to view the data you have stored. For this, you need to have some sort of debugger like st-link debugger.

In the RM, under the topic Embedded flash memory there is a table which mentions the flash memory space. You can use the main flash memory area as per the addresses mentioned.

The 0x080000C1 is likely the address of Reset_Handler, the first code the processor is running

0x08002820 + 0x20 -> 0x08002840 describes the end of the Region Table (describes initialization data), that data itself extends up to 0x0800287C

Instead of having 128KB of IROM1/FLASH (0x20000) define it as being 0x1F000 in length, then 0x0801F000 will be a safe/clear area to use, and will be consistent as code changes size, and each rebuild.

Please edit you profile with a more recognizable user name

1. compare map vs. memory map.
2. or simply declare a large static data type (ilke an array) and save data dynamically to it.

You cannot just write data into flash memory like into RAM. The ST library has functions for working with flash: erase pages and program data. Read the fine manuals and learn how it works. If you declare an array aligned on 2K (the STM32F072 flash page size) and size multiple of 2K, you can use the mentioned flash library functions to store data there.

-- pa