1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
|
/*
* 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 <http://www.gnu.org/licenses/>.
*/
#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++);
}
|
