#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 uint16_t I; // special I register, stores addresses 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) { int ret = 1; printf("loading rom %s..\n", rom); FILE *romfile; romfile = fopen(rom, "rb"); if (romfile == NULL) { fprintf(stderr, "cannot read rom %s: %s\n", rom, strerror(errno)); ret = 0; } /* read a maximum of MAX_ROM_SIZE bytes into memory starting after the reserved memory */ fread(&memory[0x200], 1, MAX_ROM_SIZE, romfile); fclose(romfile); return ret; } void chip8_init() { /* clear everything and set sane defaults */ memset(key, 0, sizeof(uint8_t) * 15); memset(video, 0, (WIDTH*HEIGHT) * sizeof(uint32_t)); memset(V, 0, sizeof(uint8_t) * 16); memset(stack, 0, (STACK_SIZE) * sizeof(uint16_t)); 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)); /* 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]; } uint8_t sinv[] = {0xBA, 0x7C, 0xD6, 0xFE, 0x54, 0xAA}; // temp for (uint8_t i = 0; i < 6; i++) { memory[0x200+i] = sinv[i]; } } void chip8_draw_sprite(int startx, int starty, uint16_t mem, uint8_t size) { /* * draw sprite located at loc of height size at startx,starty */ uint8_t byte = 0; uint8_t mask = 0x1; V[0xF] = 0; /* set collision register to 0 */ for (uint8_t byteoffset = 0; byteoffset < size; byteoffset++) { /* loop through each byte from mem to mem+size */ byte = memory[mem+byteoffset]; int bit = 0; for (mask = 0x80; mask != 0; mask >>= 1) { if (byte & mask) { uint32_t pixel = WIDTH*(starty%HEIGHT)+((startx%WIDTH)+bit); if (video[pixel] != 0) { /* if the video bit is already set, we need to set the collision register */ V[0xF] = 1; } video[pixel] ^= 0xFFFFFF; } bit++; } starty++; } } void chip8_cycle() { }