Laceys Investimigations

While writing a quick and dirty function to get some debug tiles on the screen, I forgot (it’s been over a year since I last did any DS code) that you can’t write to VRAM 8 bits at a time. I think this might be true for all RAM, though in other cases it’s likely the hardware does a 32 bit read then write. Either way, if you want to write some debug tiles to the screen make sure you write either 32 or 16 bits at a time.

The following code simply ‘makes’ two tiles in VRAM, i.e. two blocks of 64 (8×8) pixels, filling the first with 0 (for the first palette entry) and the second with 1 (for the second palette entry).

u16 *pTiles = (u16 *) BG_TILE_RAM(1);

for (i = 0; i < 64; i++)

{

	if (i > 31)
		pTiles[i] = (1 << 8) | 1;
	else
		pTiles[i] = (0);
}

Obviously this isn’t the most flexible or attractive code around, but it illustrates the point!

This entry was posted on Sunday, February 3rd, 2008 at 12:01 am and is filed under DS, Tiles. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.