add sprite functions

README.md

@@ -155,6 +155,27 @@ tms_write_reg(7, 0x1F);
 byte oldvalue = tms_regs_latch[7];
 ```
 
+### Working with sprites
+
+```c
+// set 8x8 or 16x16 sprites
+tms_set_sprite_double_size(0);
+
+// set single pixel or double pixel sprites
+tms_set_sprite_magnification(1);
+
+// define the sprite pattern 0
+tms_copy_to_vram(ghost, 8, TMS_SPRITE_PATTERNS);
+
+// define a sprite using the "sprite" struct
+tms_sprite spr;
+spr.x = 100;
+spr.y = 50;
+spr.name = 0;  // pattern 0
+spr.color = COLOR_BLACK;
+tms_set_sprite(0, &spr);
+```
+
 #### Working directly with the I/O chip interface
 
 If you want to program the VDP directly you can use the following utility functions:

lib/sprites.h

@@ -1,5 +1,39 @@
 #ifndef SPRITES_H
 #define SPRITES_H
+
+typedef struct {
+   byte y;
+   byte x;
+   byte name;
+   byte color;
+} tms_sprite;
+
+#define SIZEOF_SPRITE 4
+
+void tms_set_sprite(byte sprite_num, tms_sprite *s) {
+   word addr = TMS_SPRITE_ATTRS + (word) (sprite_num * SIZEOF_SPRITE);
+   tms_set_vram_write_addr(addr);
+
+   // TODO verify NOPs on real machine
+   // TODO is it better to use tms_copy_to_vram() ?
+   TMS_WRITE_DATA_PORT(s->y);     NOP; // y coordinate
+   TMS_WRITE_DATA_PORT(s->x);     NOP; // x coordinate
+   TMS_WRITE_DATA_PORT(s->name);  NOP; // name
+   TMS_WRITE_DATA_PORT(s->color); NOP; // color
+}
+
+void tms_set_sprite_double_size(byte size) {
+   byte regval = tms_regs_latch[1] & (REG1_SIZE_MASK ^ 0xFF);
+   if(size) regval |= REG1_SIZE_MASK;
+   tms_write_reg(1, regval);
+}
+
+void tms_set_sprite_magnification(byte m) {
+   byte regval = tms_regs_latch[1] & (REG1_MAG_MASK ^ 0xFF);
+   if(m) regval |= REG1_MAG_MASK;
+   tms_write_reg(1, regval);
+}
+
 // clears all the sprites
 void tms_clear_sprites() {
    // fills first sprite pattern with 0