nes: added attributes example

presets/nes/attributes.c

@@ -8,97 +8,41 @@
 
 /*{pal:"nes",layout:"nes"}*/
 const char PALETTE[16] = { 
-  0x03,			// background color
+  0x03,			// screen color
 
-  0x25,0x30,0x27,0x00,	// ladders and pickups
-  0x1C,0x20,0x2C,0x00,	// floor blocks
-  0x00,0x10,0x20,0x00,
-  0x06,0x16,0x26
+  0x11,0x30,0x27,0x0,	// background palette 0
+  0x1c,0x20,0x2c,0x0,	// background palette 1
+  0x00,0x10,0x20,0x0,	// background palette 2
+  0x06,0x16,0x26        // background palette 3
 };
 
-// convert nametable address to attribute address
-unsigned int nt2attraddr(unsigned int a) {
-  return (a & 0x2c00) | 0x3c0 | (a & 0x0C00) |
-    ((a >> 4) & 0x38) | ((a >> 2) & 0x07);
-}
-
-#define ATTRADR_A(x,y) (NAMETABLE_A|0x3c0|((((y)>>2)<<3)|((x)>>2)))
-
-void put_pixel(unsigned char px, unsigned char py, char color) {
-  int ntaddr, attraddr;
-  char oldch, newch;
-  char oldattr, newattr;
-  // check bounds
-  if (px >= 32*2 || py >= 30*2)
-    return;
-  // compute nametable address
-  ntaddr = NTADR_A(px>>1, py>>1);
-  // compute attribute address
-  attraddr = nt2attraddr(ntaddr);
-  //attraddr = ATTRADR_A(px>>1, py>>1);
-  // compute new character mask
-  newch = 0x80 | (px & 3) | ((py & 3) << 2);
-  // compute new attribute mask
-  newattr = color;
-  if (px & 4) newattr <<= 2;
-  if (py & 4) newattr <<= 4;
-  // wait for vsync
-  ppu_wait_frame();
-  // read old character
-  vram_adr(ntaddr);
-  vram_read(&oldch, 1);
-  vram_adr(attraddr);
-  vram_read(&oldattr, 1);
-  // write new character
-  vram_adr(ntaddr);
-  vram_put(oldch | newch);
-  // write new attribute entry
-  vram_adr(attraddr);
-  vram_put(oldattr | newattr);
-}
-
-void color_demo(void) {
-  while (1) {
-    char x = rand() & 0x3f;
-    char y = rand() & 0x3f;
-    char color = rand() & 3;
-    put_pixel(x, y, color);
-    // reset scroll position
-    vram_adr(0);
-  }
-}
-
-// draw letters
-void color_demo1(void) {
-  char ch;
-  unsigned int ntaddr,attraddr;
-  while (1) {
-    ch = rand8();
-    // use rand() for betterness
-    ntaddr = 0x2000 | (rand() & 0x1ff);
-    attraddr = nt2attraddr(ntaddr);
-    ppu_wait_frame();
-    // put character into attrib table
-    vram_adr(attraddr);
-    vram_put(0x55);
-    // put character into name table
-    vram_adr(ntaddr);
-    vram_inc(rand8() & 1);
-    vram_put(ch);
-    vram_put(ch);
-    // reset scroll position
-    vram_adr(0);
-  }
-}
+// attribute table in PRG ROM
+const char ATTRIBUTE_TABLE[0x40] = {
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // rows 0-3
+  0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, // rows 4-7
+  0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, // rows 8-11
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, // rows 12-15
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // rows 16-19
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, // rows 20-23
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, // rows 24-27
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f  // rows 28-29
+};
 
 // main function, run after console reset
 void main(void) {
-  // set palette colors
+  // set background palette colors
   pal_bg(PALETTE);
+  
+  // fill nametable with diamonds
+  vram_adr(NAMETABLE_A);
+  vram_fill(0x16, 32*30);
+  
+  // copy attribute table from PRG ROM to VRAM
+  vram_write(ATTRIBUTE_TABLE, sizeof(ATTRIBUTE_TABLE));
 
   // enable PPU rendering (turn on screen)
   ppu_on_all();
 
   // infinite loop
-  color_demo();
+  while (1) { }
 }

src/platform/nes.ts

@@ -11,6 +11,7 @@ declare var jsnes : any;
 const JSNES_PRESETS = [
   {id:'hello.c', name:'Hello World'},
   {id:'scroll.c', name:'Scrolling'},
+  {id:'attributes.c', name:'Attribute Table'},
   {id:'vrambuffer.c', name:'VRAM Buffer'},
   {id:'sprites.c', name:'Sprites'},
   {id:'metasprites.c', name:'Metasprites'},