STM32: non-initialized variables? - variables

Question

using the uvision IDE for STM32 development, I want to have some timer variables not initialized at startup. I have tried:
volatile unsigned int system_time __attribute__((section(".noinit")));
and
__attribute__((zero_init)) volatile int system_timer;
but nothing seems to work. Following the hints from elswhere, I have additionally checked NoInit at options/target/IRAM1.
Still, the variables are set to zero after reset.
Can anybody help?

Answer 1

You need to follow these steps.
declare your variable as follows:
volatile unsigned int system_time __attribute__((section(".noinit"),zero_init));
Then you have to use a scatter file to declare the execution section with the NOINIT attribute and use it with the linker.
example scatter file:
LR_IROM1 0x08000000 0x00080000 { ; load region size_region
ER_IROM1 0x08000000 0x00080000 { ; load address = execution address
*.o (RESET, +First)
*(InRoot$$Sections)
.ANY (+RO)
}
RW_IRAM1 0x20000000 UNINIT 0x00000100 { ;no init section
*(.noinit)
}
RW_IRAM2 0x20000100 0x0000FFF0 { ;all other rw data
.ANY(+RW +ZI)
}
}

Answer 2

You have to check the address of that variable from .MAP file and use the The at keyword
allows you to specify the address for uninitialized variables in your C source files. The
following example demonstrates how to locate several different variable types using the at keyword.for example......
struct link {
struct link idata *next;
char code *test;
};
struct link idata list _at_ 0x40; /* list at idata 0x40 */
char xdata text[256] _at_ 0xE000; /* array at xdata 0xE000 */
int xdata i1 _at_ 0x8000; /* int at xdata 0x8000 */
char far ftext[256] _at_ 0x02E000; /* array at xdata 0x03E000 */
void main ( void ) {
link.next = (void *) 0;
i1 = 0x1234;
text [0] = 'a';
ftext[0] = 'f';
}
I hope it helps for solving your problem.