/* * libstdgb - library of useful Game Boy operations * Copyright (C) 2016 Delwink, LLC * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License as published by * the Free Software Foundation, version 3 only. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Affero General Public License for more details. * * You should have received a copy of the GNU Affero General Public License * along with this program. If not, see . */ #include "stdgb.h" uint8_t (* const GB_OBJECTS)[GB_BYTES_PER_OBJ] = (void *) 0xDF00; static uint8_t * const DPAD_STATE = (void *) 0xDFA0; static uint8_t * const BTN_STATE = (void *) 0xDFA1; void gb_mbc5_select_rombank (uint16_t bank) { uint8_t upper = (bank & 0xFF00) >> 8; uint8_t lower = bank & 0x00FF; *((uint8_t *) 0x3000) = upper; *((uint8_t *) 0x2000) = lower; } static void invert_state (uint8_t *state) { *state = (~(*state)) & 0x0F; } void gb_update_input_state () { // this routine is copied from the official Nintendo programming manual __asm__ ("ld a, #0x20\n\t" // load flag to read d-pad input "ld (#0xFF00), a\n\t" // make input request "ld a, (#0xFF00)\n\t" // read input ports "ld a, (#0xFF00)\n\t" // do this twice for necessary delay "ld (#0xDFA0), a\n\t" // save it in *DPAD_STATE "ld a, #0x10\n\t" // load flag to read button input "ld (#0xFF00), a\n\t" // make input request "ld a, (#0xFF00)\n\t" // read input ports "ld a, (#0xFF00)\n\t" // do this six times for necessary delay "ld a, (#0xFF00)\n\t" "ld a, (#0xFF00)\n\t" "ld a, (#0xFF00)\n\t" "ld a, (#0xFF00)\n\t" "ld (#0xDFA1), a\n\t" // save it in *BTN_STATE "ld a, #0x30\n\t" // load flag to read nothing "ld (#0xFF00), a"); // disable input reads invert_state (DPAD_STATE); invert_state (BTN_STATE); } uint8_t gb_dpad_down (uint8_t direction) { return *DPAD_STATE & direction; } uint8_t gb_button_down (uint8_t button) { return *BTN_STATE & button; } void gb_enable_vblank () { *GB_INT_ENABLE |= GB_INT_VBLANK; gb_enable_interrupts (); } void gb_wait_vblank () { do { gb_halt (); } while (!gb_have_vblank ()); } void gb_define_tile (uint8_t start, const uint8_t *data) { uint8_t *tiles = GB_TILE_DATA; gb_memcpy (&tiles[start * GB_BYTES_PER_TILE], data, GB_BYTES_PER_TILE); } void gb_set_view (uint8_t x, uint8_t y) { *GB_SCROLL_X = x; *GB_SCROLL_Y = y; } void gb_shift_view (int8_t x, int8_t y) { *GB_SCROLL_X += x; *GB_SCROLL_Y += y; } static void copy_objects () { __asm__ ("ld a,#0xDF\n\t" // specify that objects are at 0xDF00 "ld (0xFF46),a\n\t" // start DMA copy "ld a,#0x28\n" // set wait counter to 40 "obj_copy_wait:\n\t" "dec a\n\t" // decrement counter "jr nz,obj_copy_wait"); // continue to wait until counter is zero } void gb_init_objects () { gb_memcpy (GB_HRAM, (uint8_t *) copy_objects, 12); memset (GB_OBJECTS, 0, GB_NUM_OBJECTS * GB_BYTES_PER_OBJ); gb_update_objects (); } void gb_update_objects () { __asm__ ("jp 0xFF80"); // real function is at HRAM } void gb_memcpy (uint8_t *dest, const uint8_t *src, uint8_t n) { while (n--) *(dest++) = *(src++); }