Well, the collision map uses 8x8 pixel for each tile, so you need to devide coordinate by the size of your collide box.
Also, to have the correct tile, you must add map size * y , not only y.
u16 getCollisionTile(u16 x, u16 y) {
u16 *ptrMap = (u16 *) &col + (y>>3)*32+ (x>>3);
return (*ptrMap);
}
But, you also need to take care of sprite size and where is the point that you need to use to check the collide box.
Here is an example, "not so good" but that uses a point near middle of sprite to test hit box with back ground (so I use x+8, y+8).
/*---------------------------------------------------------------------------------
Animated Sprite demo
-- alekmaul
Sprite from Stephen "Redshrike" Challener), http://opengameart.org
---------------------------------------------------------------------------------*/
#include <snes.h>
extern char gfxpsrite, gfxpsrite_end;
extern char palsprite, palsprite_end;
extern char patterns, patterns_end;
extern char palette, palette_end;
extern char map, map_end;
extern char col, col_e;
#define FRAMES_PER_ANIMATION 3 // 3 sprites per direction
//---------------------------------------------------------------------
// The Monster sprite
//---------------------------------------------------------------------
typedef struct
{
short x, y;
int gfx_frame;
int state;
int anim_frame;
int flipx;
} Monster;
//---------------------------------------------------------------------
// The state of the sprite (which way it is walking)
//---------------------------------------------------------------------
enum SpriteState {W_DOWN = 0, W_UP = 1, W_RIGHT = 2, W_LEFT = 2};
//---------------------------------------------------------------------
// Screen dimentions
//---------------------------------------------------------------------
enum {SCREEN_TOP = 0, SCREEN_BOTTOM = 224, SCREEN_LEFT = 0, SCREEN_RIGHT = 256};
char sprTiles[9]={0,2,4, 6,8,10, 12,14,32}; // Remeber that sprites are interleave with 128 pix width,
u16 getCollisionTile(u16 x, u16 y) {
u16 *ptrMap = (u16 *) &col + (y>>3)*32 + (x>>3);
return (*ptrMap);
}
//---------------------------------------------------------------------------------
int main(void) {
unsigned short pad0,i;
Monster monster = {10,10};
// Initialize SNES
consoleInit();
// Init Sprites gfx and palette with default size of 16x16
oamInitGfxSet(&gfxpsrite, (&gfxpsrite_end-&gfxpsrite), &palsprite, (&palsprite_end-&palsprite), 0, 0x0000, OBJ_SIZE16);
// Copy tiles to VRAM
bgInitTileSet(0, &patterns, &palette, 0, (&patterns_end - &patterns), (&palette_end - &palette), BG_16COLORS, 0x4000);
// Copy Map to VRAM
bgInitMapSet(0, &map, (&map_end - &map),SC_32x32, 0x1000);
// Define sprites parameters
oamSet(0, monster.x, monster.y, 0, 0, 0, 0, 0);
oamSetEx(0, OBJ_SMALL, OBJ_SHOW);
// Now Put in 16 color mode and disable all backgrounds
setMode(BG_MODE1,0); bgSetDisable(1); bgSetDisable(2);
// Wait VBL 'and update sprites too ;-)
WaitForVBlank();
// Wait for nothing 
while(1) {
// Refresh pad values
// no more need with last lib scanPads();
// Get current #0 pad
pad0 = padsCurrent(0);
if (pad0) {
// Update sprite with current pad
if(pad0 & KEY_UP) {
if (getCollisionTile((monster.x+8), ((monster.y) - 1)) == 0) {
if(monster.y >= SCREEN_TOP) monster.y--;
}
monster.state = W_UP;
monster.flipx = 0;
}
if(pad0 & KEY_LEFT) {
if (getCollisionTile(((monster.x) - 1), (monster.y+8)) == 0) {
if(monster.x >= SCREEN_LEFT) monster.x--;
}
monster.state = W_LEFT;
monster.flipx = 1;
}
if(pad0 & KEY_RIGHT) {
if (getCollisionTile(((monster.x +16) +1), (monster.y+8)) == 0) {
if(monster.x <= SCREEN_RIGHT) monster.x++;
}
monster.state = W_LEFT;
monster.flipx = 0;
}
if(pad0 & KEY_DOWN) {
if (getCollisionTile((monster.x+8), ((monster.y+16) + 1)) == 0) {
if(monster.y <= SCREEN_BOTTOM) monster.y++;
}
monster.state = W_DOWN;
monster.flipx = 0;
}
monster.anim_frame++;
if(monster.anim_frame >= FRAMES_PER_ANIMATION){
monster.anim_frame = 0;
}
}
// Now, get current sprite in current animation
monster.gfx_frame = sprTiles[monster.anim_frame + monster.state*FRAMES_PER_ANIMATION ];
oamSet(0, monster.x, monster.y, 3, monster.flipx, 0, monster.gfx_frame, 0);
// Wait VBL 'and update sprites too ;-) )
WaitForVBlank();
}
return 0;
}
