66 lines
1.6 KiB
C
66 lines
1.6 KiB
C
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/*
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On the NES, you can't write to video RAM while the PPU
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is active, so you have to do it during the vertical blank.
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We have a module (vrambuf) which fills up a buffer with video
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data, then NESLib writes it to VRAM during the NMI interrupt.
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*/
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#include "neslib.h"
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#include <string.h>
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#include <stdio.h>
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// VRAM buffer module
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#include "vrambuf.h"
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//#link "vrambuf.c"
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// link the pattern table into CHR ROM
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//#link "chr_generic.s"
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// function to scroll window up and down until end
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void scroll_demo() {
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int x = 0; // x scroll position
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int y = 0; // y scroll position
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int dy = 1; // y scroll direction
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// 32-character array for string-building
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char str[32];
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// clear string array
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memset(str, 0, sizeof(str));
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// infinite loop
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while (1) {
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// write message to string array
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sprintf(str, "%6x %6d", y, y);
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// write string array into VRAM buffer
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// if buffer is full this will wait for next frame
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vrambuf_put(NTADR_A(2,y%30), str, 32);
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// update y variable
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y += dy;
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// change direction when hitting either edge of scroll area
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if (y >= 479) dy = -1;
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if (y == 0) dy = 1;
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// set scroll (shadow) registers
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scroll(x, y);
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}
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}
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// main function, run after console reset
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void main(void) {
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// set palette colors
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pal_col(0,0x02); // set screen to dark blue
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pal_col(1,0x14); // pink
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pal_col(2,0x20); // grey
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pal_col(3,0x30); // white
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// clear vram buffer
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vrambuf_clear();
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// set NMI handler
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set_vram_update(updbuf);
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// enable PPU rendering (turn on screen)
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ppu_on_all();
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// scroll window back and forth
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scroll_demo();
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}
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