Array asm function in C

Question

How do I return values of this array asm function in C? I'm not sure how to use sprintf in this case.

I need to show in the display some values before and after the array function.

//*****************************************************************************
//FUNCTION: InitXa
//DESCRIPTION: array X of size N with a constant value V, using pointers:
//PARAMETERS: r0 = *X
//            r1 = Size N
//            r2 = Value V
//RETURN: None
//*****************************************************************************

// local register definitions
#define        rXA        r0        // register to hold address of X
#define        rN    r1    // register to hold value of N
#define        rV    r2    // register to hold value of V

__asm void InitXa (uint32 *X, uint32 N, uint32 V)
{
    STR rN, [rXA]     ; Store the value at first address of array.
    SUBS rV, #1       ; decrement the count 
loop
    STR rN,[rXA],#4   ; Store the value and increment the pointer
    SUBS rV,rV,#1     ; decrement the count
    BNE loop          ; branch until the count is 0
    BX lr             ; return to caller
}

C part of the code:

uint32 X = {10, 2, 3};
uint32 N = 10;
uint32 V = 3;
uint32 result32;

sprintf (str, "%d", result32);    //  **display the first few values of the array before     initialization on the top line of the OLED.**

InitXa (X, N, V); 

sprintf (str, "%d", result32); //**Use the second line to display values after** initialization.

Answer 1

It looks like you're unfamiliar with how to access array elements. Also, the result32 value is not being used, so no need to print it. I think this is what you intended:

printf("Before calling asm function: %d, %d, %d \n", X[0], X[1], X[2]);

InitXa (X, N, V); 

printf("After calling asm function: %d, %d, %d \n", X[0], X[1], X[2]);

PS - I would recommend reading this book: http://www.amazon.com/The-Programming-Language-Brian-Kernighan/dp/0131101633/ref=sr_1_2?ie=UTF8&qid=1391790669&sr=8-2&keywords=k%26r+the+c+programming+language

The writing style is rather dry, but it helped me understand C 30 years ago and it's just as valid today.