Weird behaviour with data in flash ( STM32F412RE)

[Bertrand1]

Hello,

I have some application parameters stored in flash area, declared like this :

__attribute__((__section__(".storageFlash"))) const parametersTable_t flashParameters;

The linker script has been modified as follow:

/* Specify the memory areas */

MEMORY

{

RAM (xrw)     : ORIGIN = 0x20000000, LENGTH = 256K

FLASH (rx)     : ORIGIN = 0x8000000, LENGTH = 384K

PARAMETERS_STORAGE (rx)   : ORIGIN = 0x08060000, LENGTH = 64K

CALIBRATION_STORAGE (rx) : ORIGIN = 0x08068000, LENGTH = 64K

}

....

 .storageFlash (NOLOAD) :

 {

   . = ALIGN(4);

   *(storageFlash)

   . = ALIGN(4);

 } >PARAMETERS_STORAGE

In my program I do a simple copy on a local data or make a comparaison with Ram data like this : temp = flashParameters.version;

With Atollic , I can read that flashParameters.version = 12 but temp = 0!!

If I read the raw memory I can also find 12.

I don't understand why the programm read always 0 instead of 12.

Thanks for your help

Bertrand

[Tesla DeLorean]

Some of your memory regions overlap.

Check the addresses in .MAP

Check the code generated in the listing file (.LST, .LSS, whatever)

The optimizer might assume a const region with nothing defined in it might be zero

[Bertrand1]

Thanks Clive for your prompt reply.

I checked .map : flashParameter is located at 0x08060000.

It is correct according to the linker script.

I am try to understand the .list file but too low level for me. Here an extract :

    temp = flashParameters.version;
    temp2 = flashParam.version;
    sprintf(sBuf, "  Stored parameters version is %d ...", temp);
 8019988:	4c25      	ldr	r4, [pc, #148]	; (8019a20 <isConfigInFlashValid+0xac>)
 801998a:	2200      	movs	r2, #0
 801998c:	4925      	ldr	r1, [pc, #148]	; (8019a24 <isConfigInFlashValid+0xb0>)
 801998e:	4620      	mov	r0, r4
 8019990:	f004 f98c 	bl	801dcac <siprintf>

[TDK]

Maybe it's just optimized out or the line has been shuffled somewhere else.

[Bertrand1]

I don't think so. I removed almost all optimization and I do a comparaison after that and it fails.

12 == 12 -> Wrong!

I am crazy 😉

[Bertrand1]

Additionnal information : If I place the code in the main.c ( uint16_t test = flashParameters.version). it works!

For today, I do a memcpy on a RAM structure in a step before ( I don't know how to explain, but I do this memcpy one step before in the call stack)

[waclawek.jan]

Read out that FLASH area - does it contain what you think it should?

Step through disasm and observe registers.

JW

[Bertrand1]

Thanks for your help.

I read out the flash and I can find the right value on it.

For disassembly analysis with register, I have a lack ok knowledge to do it yet. :(

Bertrand

[waclawek.jan]

I don't know what development environment are you using, but in IDEs it's usually just about clicking into the disasm window and single-stepping as usually. Shouldn't be that hard to try.

JW

[Bertrand1]

I am on Atollic Studio 9.3.

Not difficult to find the disassembly but to understand what the programm do exactly.