How to set a static array in a specific memory location

Question

I am running this c program in gcc. The below works for one variable.

#define dataBlk_tx0 ((volatile unsigned int *) 0x20000ACB)

But if I want to create an array and write to it how would I do this, this array needs to be defined before main?

#define dataBlk_tx0 ((volatile unsigned int * x[8]) 0x20000ACB)

main{

dataBlk_tx0[0] = 5;

}

Why do you need to create an array? The array is already there, it's the memory dataBlk_tx0 points to. Just use it like this: dataBlk_tx0[0], dataBlk_tx0[1] etc. Just use #define dataBlk_tx0 ((volatile unsigned int *) 0x20000ACB) (without the final ;) — Jabberwocky
– Jabberwocky, Commented Nov 24, 2020 at 13:47
You could define it as #define dataBlk_tx0 ((volatile unsigned int (*)[8]) 0x20000ACB), but then you would need to access the elements using constructions such as (*dataBlk_tx0)[0] = 5; or dataBlk_tx0[0][0] = 5;, so it would be much simpler to follow @Jabberwocky's suggestion in the comment above to avoid the need for the extra level of dereferencing/indexing. — Ian Abbott
– Ian Abbott, Commented Nov 24, 2020 at 13:56

GandhiGandhi · Accepted Answer · 2020-11-24 13:54:11Z

2

If you want to read or write directly to that address and memory, you can do it like this:

volatile unsigned int * dataBlk_tx0 = (unsigned int *)0x20000ACB;

int main () {
    dataBlk_tx0[0] = 5;
    return 0;
}

If you want to create an array in a specific memory region (like Flash vs RAM on a micocontroller), then you'll need to look into linker scripts.

answered Nov 24, 2020 at 13:54

GandhiGandhi

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