NDS adventures: code for clearing the screen background

I’ve been getting my feet wet with developing for the Nintendo DS. While I can’t afford the official SDK (nor would they sell it to me, a lowly student with no intention to sell games yet), I installed devkitARM, an unofficial SDK developed by “amateurs”.

Down to the basics

First things first, I wanted to learn how to clear the screen (actually, there are two screens in the NDS, but let’s leave that aside for now).

Actually, there are several ways to clear to background or, better said, painting it black.
One way is iterating over each pixel in the display buffer (BG_BMP_RAM_SUB) and setting it’s color as black (RGB 0,0,0).

/* Clears the background of the sub screen. */
void clearBottomScreen()
{
    u16* video_buffer_main = (u16*)BG_BMP_RAM_SUB(0);
    int i;
    for (i = 0; i < SCREEN_HEIGHT*SCREEN_WIDTH; i++)
        video_buffer_main[i] = RGB15(0,0,0);
}

One other way I read somewhere and which is surely more efficient involves doing something similar over DMA transfers, painting much more than a pixel at a time. I shall investigate this.