// --------------------------------------------------------------------

//

// Super Simple Background Text Scroller v1.0

//

// Not terribly unlike how we did it in the c64 days. Although this

// is C and on the c64 we used asm, the concept is very much similar.

// This source is set up so you can tweak the speed and the row to

// scroll the text on... In actuality there are a number of ways

// to perform a scroller like this, but I tried to break it down

// in a simple fashion to make it easier to understand (hopefully!)

//

// r6502 - 2004-04-02

//

// Note: tabs == 4 on my setup

//

// --------------------------------------------------------------------

#include <gba_base.h>

#include <gba_video.h>

#include <gba_systemcalls.h>

#include <gba_interrupt.h>

#include "C:\Users\Chris\Desktop\Uni\Trimester 5 2015\GBA DEV\devkitPro\examples\gba\graphics\SimpleBGScroll\font/r6502_portfont.bin"

// --------------------------------------------------------------------

#define MAPADDRESS MAP_BASE_ADR(31) // our base map address

#define DELAY 2 // slow things down

#define TILEWIDTH 8 // how much to scroll

#define ROW 10 // what row to place text at

// --------------------------------------------------------------------

const u16 palette[] = {

RGB8(0x40,0x80,0xc0),

RGB8(0xFF,0xFF,0xFF),

RGB8(0xF5,0xFF,0xFF),

RGB8(0xDF,0xFF,0xF2),

RGB8(0xCA,0xFF,0xE2),

RGB8(0xB7,0xFD,0xD8),

RGB8(0x2C,0x4F,0x8B)

};

// --------------------------------------------------------------------

const u8 message[] = {

" " \

"Hello, this is an example of an oldschool simple tile scroller " \

"not unlike how it was done in days of yore. The '@' symbol " \

"at the top of your screen is intentional, to dispel the illusion " \

"of this scroller, to demonstrate the simple concept behind it. " \

"Check out the source to learn how it works. It is very simple! " \

"This exercise brought to you by r6502... " \

"Text is about to restart... "

};

// --------------------------------------------------------------------

void updatescrolltext(u32 idx)

{

u32 i;

u16 *temppointer;

temppointer = (u16 *)MAPADDRESS + (ROW * 32);

// write out a whole row of text to the map

for(i=0; i<32; i++)

{

// check for end of message so we can wrap around properly

if(message[idx] == 0) idx = 0;

// write a character - we subtract 32, because the font graphics

// start at tile 0, but our text is in ascii (starting at 32 and up)

// in other words, tile 0 is a space in our font, but in ascii a

// space is 32 so we must account for that difference between the two.

*temppointer++ = message[idx++] - 32;

}

}

int main() {

// Set up the interrupt handlers

irqInit();

// Enable Vblank Interrupt to allow VblankIntrWait

irqEnable(IRQ_VBLANK);

// Allow Interrupts

REG_IME = 1;

u32 i, scrollx, scrolldelay, textindex;

u16 *temppointer;

// load the palette for the background, 7 colors

temppointer = BG_COLORS;

for(i=0; i<7; i++) {

*temppointer++ = palette[i];

}

// load the font into gba video mem (48 characters, 4bit tiles)

CpuFastSet(r6502_portfont_bin, (u16*)VRAM,(r6502_portfont_bin_size/4) | COPY32);

// clear screen map with tile 0 ('space' tile) (256x256 halfwords)

*((u32 *)MAP_BASE_ADR(31)) =0;

CpuFastSet( MAP_BASE_ADR(31), MAP_BASE_ADR(31), FILL | COPY32 | (0x800/4));

// set screen H and V scroll positions

BG_OFFSET[0].x = 0; BG_OFFSET[0].y = 0;

// initialize our variables

scrollx = 0;

textindex = 0;

scrolldelay = 0;

// put the '@' symbol on the top of the screen to show how

// the screen is only scrolling 7 pixels - to reveal the

// illusion of how the scroller works

*((u16 *)MAPADDRESS + 1) = 0x20; // 0x20 == '@'

// draw a row of text from beginning of message

updatescrolltext(0);

// set the screen base to 31 (0x600F800) and char base to 0 (0x6000000)

BGCTRL[0] = SCREEN_BASE(31);

// screen mode & background to display

SetMode( MODE_0 | BG0_ON );

while(1) {

VBlankIntrWait();

// check if we reached our delay

if(scrolldelay == DELAY) {

// yes, the delay is complete, so let's reset it

scrolldelay = 0;

// check if we reached our scrollcount

if(scrollx == (TILEWIDTH-1)) {

// yes, we've scrolled enough, so let's reset the count

scrollx = 0;

// check if we reached the end of our scrolltext

// and if so we need to restart our index

if(message[textindex] == 0) textindex = 0;

else textindex++;

// finally, let's update the scrolltext with the current text index

updatescrolltext(textindex);

}

else scrollx++;

}

else scrolldelay++;

// update the hardware horizontal scroll register

BG_OFFSET[0].x = scrollx;

}

}