more initialisation and added the fontset

fontset also loaded into memory at 0x0, we have 0x0 to 0x1FF free for anything we want, that is where the interpreter is meant to be

2 files changed, 47 insertions, 4 deletions

diff --git a/chip8.c b/chip8.c
index 3c41117..2ce911f 100644
--- a/chip8.c
+++ b/chip8.c
@@ -1,5 +1,6 @@
 #include "chip8.h"
 
+uint16_t opcode;		// 2 byte opcode
 uint8_t key[KEY_SIZE]; 		// hex key input
 uint32_t video[WIDTH*HEIGHT]; 	// video memory TODO: video should be 8 bit not 32
 uint8_t V[16];			// registers - 0x0 to 0xF
@@ -8,6 +9,30 @@ uint16_t PC;			// program counter
 uint8_t SP;			// stack pointer
 uint16_t stack[STACK_SIZE];	// stack, for address storage when using subroutines, maximum of 16 levels of nested subroutines
 uint8_t memory[MEMORY_SIZE];	// 4KB of program memory
+int draw_flag;			// draw flag, when 1 the screen will be drawn
+uint8_t delay_timer;		// delay timer, decremented by one at 60hz, at 0 do nothing
+uint8_t sound_timer;		// sound timer, decremented by one at 60hz, while it is > 0 a beep is played
+
+/* 0 - F hexidecimal font as required by the chip8 spec */
+uint8_t chip8_fontset[80] =
+{
+	0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
+	0x20, 0x60, 0x20, 0x20, 0x70, // 1
+	0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
+	0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
+	0x90, 0x90, 0xF0, 0x10, 0x10, // 4
+	0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
+	0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
+	0xF0, 0x10, 0x20, 0x40, 0x40, // 7
+	0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
+	0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
+	0xF0, 0x90, 0xF0, 0x90, 0x90, // A
+	0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
+	0xF0, 0x80, 0x80, 0x80, 0xF0, // C
+	0xE0, 0x90, 0x90, 0x90, 0xE0, // D
+	0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
+	0xF0, 0x80, 0xF0, 0x80, 0x80  // F
+};
 
 int
 load_rom(char *rom)
@@ -32,10 +57,26 @@ load_rom(char *rom)
 void
 chip8_init()
 {
-	/* clear everything */
-	memset(key, 0, 15);
+	/* clear everything and set sane defaults */
+	memset(key, 0, sizeof(uint8_t) * 15);
 	memset(video, 0, (WIDTH*HEIGHT) * sizeof(uint32_t));
-	memset(V, 0, 16);
+	memset(V, 0, sizeof(uint8_t) * 16);
 	memset(stack, 0, (STACK_SIZE) * sizeof(uint16_t));
-	memset(memory, 0, MEMORY_SIZE);
+	memset(memory, 0, sizeof(uint8_t) * MEMORY_SIZE);
+
+	PC = 0x200; 		// set program counter to where roms are stored
+	opcode = 0;
+	I = 0;
+	SP = 0;
+	draw_flag = 1;		// draw by default i guess
+	delay_timer = 0;
+	sound_timer = 0;
+	srand(time(NULL));	// seed rng
+
+	/* load font into memory at 0x00: we have 0x00 to 0x1FF free for anything we want */
+	//TODO: add whole alphabet, then can write a rom to write strings or something
+	for (uint8_t i = 0; i < 80; i++)
+	{
+		memory[0x0 + i] = chip8_fontset[i];
+	}
 }
diff --git a/chip8.h b/chip8.h
index 7301c45..4faa6e4 100644
--- a/chip8.h
+++ b/chip8.h
@@ -2,9 +2,11 @@
 #define CHIP8_H
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
 #include <errno.h>
+#include <time.h>
 
 #define WIDTH 64
 #define HEIGHT 32