summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/audio/redbaron.c
blob: 3f28a44f58fbb1011b962de78e5ac7879a5e23e6 (plain) (blame)
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
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
/*************************************************************************

    Atari Red Baron hardware

*************************************************************************/
/*

    Red Baron sound notes:
    bit function
    7-4 explosion volume
    3   start led
    2   shot (machine gun sound)
    1   squeal (nosedive sound)
    0   POTSEL (rb_input_select)
*/

#include <math.h>
#include "driver.h"
#include "streams.h"
#include "includes/bzone.h"
#include "sound/pokey.h"

#define OUTPUT_RATE		(48000)

/* Statics */
static INT16 *vol_lookup = NULL;

static INT16 vol_crash[16];

static sound_stream *channel;
static int latch;
static int poly_counter;
static int poly_shift;

static int filter_counter;

static int crash_amp;
static int shot_amp;
static int shot_amp_counter;

static int squeal_amp;
static int squeal_amp_counter;
static int squeal_off_counter;
static int squeal_on_counter;
static int squeal_out;

WRITE8_HANDLER( redbaron_sounds_w )
{
	/* If sound is off, don't bother playing samples */
	if( data == latch )
		return;

	stream_update(channel);
    latch = data;
    rb_input_select = data & 1;
}

#ifdef UNUSED_FUNCTION
WRITE8_DEVICE_HANDLER( redbaron_pokey_w )
{
    if( latch & 0x20 )
        pokey_w(device, offset, data);
}
#endif

static STREAM_UPDATE( redbaron_sound_update )
{
	stream_sample_t *buffer = outputs[0];
	while( samples-- )
	{
		int sum = 0;

		/* polynome shifter E5 and F4 (LS164) clocked with 12kHz */
		poly_counter -= 12000;
		while( poly_counter <= 0 )
		{
			poly_counter += OUTPUT_RATE;
			if( ((poly_shift & 0x0001) == 0) == ((poly_shift & 0x4000) == 0) )
				poly_shift = (poly_shift << 1) | 1;
			else
				poly_shift <<= 1;
		}

		/* What is the exact low pass filter frequency? */
		filter_counter -= 330;
		while( filter_counter <= 0 )
		{
			filter_counter += OUTPUT_RATE;
			crash_amp = (poly_shift & 1) ? latch >> 4 : 0;
		}
		/* mix crash sound at 35% */
		sum += vol_crash[crash_amp] * 35 / 100;

		/* shot not active: charge C32 (0.1u) */
		if( (latch & 0x04) == 0 )
            shot_amp = 32767;
        else
		if( (poly_shift & 0x8000) == 0 )
        {
			if( shot_amp > 0 )
			{
                /* discharge C32 (0.1u) through R26 (33k) + R27 (15k)
                 * 0.68 * C32 * (R26 + R27) = 3264us
                 */
//              #define C32_DISCHARGE_TIME (int)(32767 / 0.003264);
				/* I think this is to short. Is C32 really 1u? */
				#define C32_DISCHARGE_TIME (int)(32767 / 0.03264);
				shot_amp_counter -= C32_DISCHARGE_TIME;
				while( shot_amp_counter <= 0 )
				{
					shot_amp_counter += OUTPUT_RATE;
					if( --shot_amp == 0 )
						break;
				}
				/* mix shot sound at 35% */
				sum += vol_lookup[shot_amp] * 35 / 100;
            }
        }


		if( (latch & 0x02) == 0 )
			squeal_amp = 0;
		else
		{
			if( squeal_amp < 32767 )
			{
				/* charge C5 (22u) over R3 (68k) and CR1 (1N914)
                 * time = 0.68 * C5 * R3 = 1017280us
                 */
				#define C5_CHARGE_TIME (int)(32767 / 1.01728);
				squeal_amp_counter -= C5_CHARGE_TIME;
				while( squeal_amp_counter <= 0 )
				{
					squeal_amp_counter += OUTPUT_RATE;
					if( ++squeal_amp == 32767 )
						break;
				}
			}

			if( squeal_out )
			{
				/* NE555 setup as pulse position modulator
                 * C = 0.01u, Ra = 33k, Rb = 47k
                 * frequency = 1.44 / ((33k + 2*47k) * 0.01u) = 1134Hz
                 * modulated by squeal_amp
                 */
				squeal_off_counter -= (1134 + 1134 * squeal_amp / 32767) / 3;
				while( squeal_off_counter <= 0 )
				{
					squeal_off_counter += OUTPUT_RATE;
					squeal_out = 0;
				}
			}
			else
			{
				squeal_on_counter -= 1134;
				while( squeal_on_counter <= 0 )
				{
					squeal_on_counter += OUTPUT_RATE;
					squeal_out = 1;
                }
            }
		}

		/* mix sequal sound at 40% */
        if( squeal_out )
			sum += 32767 * 40 / 100;

		*buffer++ = sum;
	}
}

static DEVICE_START( redbaron_sound )
{
	int i;

	vol_lookup = auto_alloc_array(device->machine, INT16, 32768);
	for( i = 0; i < 0x8000; i++ )
		vol_lookup[0x7fff-i] = (INT16) (0x7fff/exp(1.0*i/4096));

	for( i = 0; i < 16; i++ )
	{
		/* r0 = R18 and R24, r1 = open */
        double r0 = 1.0/(5600 + 680), r1 = 1/6e12;

		/* R14 */
        if( i & 1 )
			r1 += 1.0/8200;
		else
			r0 += 1.0/8200;
		/* R15 */
        if( i & 2 )
			r1 += 1.0/3900;
		else
			r0 += 1.0/3900;
		/* R16 */
        if( i & 4 )
			r1 += 1.0/2200;
		else
			r0 += 1.0/2200;
		/* R17 */
        if( i & 8 )
			r1 += 1.0/1000;
		else
			r0 += 1.0/1000;
		r0 = 1.0/r0;
		r1 = 1.0/r1;
		vol_crash[i] = 32767 * r0 / (r0 + r1);
	}

	channel = stream_create(device, 0, 1, OUTPUT_RATE, 0, redbaron_sound_update);
}


DEVICE_GET_INFO( redbaron_sound )
{
	switch (state)
	{
		/* --- the following bits of info are returned as pointers to data or functions --- */
		case DEVINFO_FCT_START:							info->start = DEVICE_START_NAME(redbaron_sound);break;

		/* --- the following bits of info are returned as NULL-terminated strings --- */
		case DEVINFO_STR_NAME:							strcpy(info->s, "Red Baron Custom");			break;
		case DEVINFO_STR_SOURCE_FILE:						strcpy(info->s, __FILE__);						break;
	}
}