mirror of
https://github.com/sehugg/8bitworkshop.git
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105 lines
2.3 KiB
C
105 lines
2.3 KiB
C
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#include "neslib.h"
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#include <string.h>
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#include <stdlib.h>
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// link the pattern table into CHR ROM
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//#link "chr_generic.s"
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/*{pal:"nes",layout:"nes"}*/
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const char PALETTE[16] = {
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0x03, // background color
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0x25,0x30,0x27,0x00, // ladders and pickups
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0x1C,0x20,0x2C,0x00, // floor blocks
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0x00,0x10,0x20,0x00,
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0x06,0x16,0x26
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};
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// convert nametable address to attribute address
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unsigned int nt2attraddr(unsigned int a) {
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return (a & 0x2c00) | 0x3c0 | (a & 0x0C00) |
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((a >> 4) & 0x38) | ((a >> 2) & 0x07);
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}
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#define ATTRADR_A(x,y) (NAMETABLE_A|0x3c0|((((y)>>2)<<3)|((x)>>2)))
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void put_pixel(unsigned char px, unsigned char py, char color) {
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int ntaddr, attraddr;
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char oldch, newch;
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char oldattr, newattr;
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// check bounds
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if (px >= 32*2 || py >= 30*2)
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return;
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// compute nametable address
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ntaddr = NTADR_A(px>>1, py>>1);
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// compute attribute address
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attraddr = nt2attraddr(ntaddr);
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//attraddr = ATTRADR_A(px>>1, py>>1);
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// compute new character mask
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newch = 0x80 | (px & 3) | ((py & 3) << 2);
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// compute new attribute mask
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newattr = color;
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if (px & 4) newattr <<= 2;
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if (py & 4) newattr <<= 4;
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// wait for vsync
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ppu_wait_frame();
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// read old character
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vram_adr(ntaddr);
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vram_read(&oldch, 1);
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vram_adr(attraddr);
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vram_read(&oldattr, 1);
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// write new character
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vram_adr(ntaddr);
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vram_put(oldch | newch);
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// write new attribute entry
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vram_adr(attraddr);
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vram_put(oldattr | newattr);
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}
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void color_demo(void) {
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while (1) {
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char x = rand() & 0x3f;
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char y = rand() & 0x3f;
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char color = rand() & 3;
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put_pixel(x, y, color);
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// reset scroll position
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vram_adr(0);
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}
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}
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// draw letters
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void color_demo1(void) {
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char ch;
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unsigned int ntaddr,attraddr;
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while (1) {
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ch = rand8();
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// use rand() for betterness
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ntaddr = 0x2000 | (rand() & 0x1ff);
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attraddr = nt2attraddr(ntaddr);
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ppu_wait_frame();
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// put character into attrib table
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vram_adr(attraddr);
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vram_put(0x55);
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// put character into name table
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vram_adr(ntaddr);
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vram_inc(rand8() & 1);
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vram_put(ch);
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vram_put(ch);
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// reset scroll position
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vram_adr(0);
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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_bg(PALETTE);
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// enable PPU rendering (turn on screen)
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ppu_on_all();
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// infinite loop
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color_demo();
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}
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