1 // license:GPL-2.0+
2 // copyright-holders:Juergen Buchmueller
3 /****************************************************************************
4 *
5 * geebee.cpp
6 *
7 * sound driver
8 * juergen buchmueller <pullmoll@t-online.de>, jan 2000
9 *
10 ****************************************************************************/
11
12 #include "emu.h"
13 #include "audio/geebee.h"
14
15
16 DEFINE_DEVICE_TYPE(GEEBEE_SOUND, geebee_sound_device, "geebee_sound", "Gee Bee Custom Sound")
17
geebee_sound_device(const machine_config & mconfig,const char * tag,device_t * owner,uint32_t clock)18 geebee_sound_device::geebee_sound_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
19 : device_t(mconfig, GEEBEE_SOUND, tag, owner, clock),
20 device_sound_interface(mconfig, *this),
21 m_decay(nullptr),
22 m_channel(nullptr),
23 m_sound_latch(0),
24 m_sound_signal(0),
25 m_volume(0),
26 m_volume_timer(nullptr),
27 m_noise(0),
28 m_vcount(0)
29 {
30 }
31
32
33 //-------------------------------------------------
34 // device_start - device-specific startup
35 //-------------------------------------------------
36
device_start()37 void geebee_sound_device::device_start()
38 {
39 m_decay = std::make_unique<uint16_t[]>(32768);
40
41 for (int i = 0; i < 0x8000; i++)
42 m_decay[0x7fff - i] = (int16_t) (0x7fff/exp(1.0*i/4096));
43
44 /* 1V = HSYNC = 18.432MHz / 3 / 2 / 384 = 8000Hz */
45 m_channel = stream_alloc(0, 1, clock() / 3 / 2 / 384);
46 m_vcount = 0;
47
48 m_volume_timer = timer_alloc(TIMER_VOLUME_DECAY);
49
50 save_item(NAME(m_sound_latch));
51 save_item(NAME(m_sound_signal));
52 save_item(NAME(m_volume));
53 save_item(NAME(m_noise));
54 save_item(NAME(m_vcount));
55 }
56
device_timer(emu_timer & timer,device_timer_id id,int param,void * ptr)57 void geebee_sound_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
58 {
59 switch (id)
60 {
61 case TIMER_VOLUME_DECAY:
62 if (--m_volume < 0)
63 m_volume = 0;
64 break;
65
66 default:
67 throw emu_fatalerror("Unknown id in geebee_device::device_timer");
68 }
69 }
70
sound_w(u8 data)71 void geebee_sound_device::sound_w(u8 data)
72 {
73 m_channel->update();
74 m_sound_latch = data;
75 m_volume = 0x7fff; /* set volume */
76 m_noise = 0x0000; /* reset noise shifter */
77 /* faster decay enabled? */
78 if( m_sound_latch & 8 )
79 {
80 /*
81 * R24 is 10k, Rb is 0, C57 is 1uF
82 * charge time t1 = 0.693 * (R24 + Rb) * C57 -> 0.22176s
83 * discharge time t2 = 0.693 * (Rb) * C57 -> 0
84 * Then C33 is only charged via D6 (1N914), not discharged!
85 * Decay:
86 * discharge C33 (1uF) through R50 (22k) -> 0.14058s
87 */
88 attotime period = attotime::from_hz(32768) * 14058 / 100000;
89 m_volume_timer->adjust(period, 0, period);
90 }
91 else
92 {
93 /*
94 * discharge only after R49 (100k) in the amplifier section,
95 * so the volume shouldn't very fast and only when the signal
96 * is gated through 6N (4066).
97 * I can only guess here that the decay should be slower,
98 * maybe half as fast?
99 */
100 attotime period = attotime::from_hz(32768) * 29060 / 100000;
101 m_volume_timer->adjust(period, 0, period);
102 }
103 }
104
105 //-------------------------------------------------
106 // sound_stream_update - handle a stream update
107 //-------------------------------------------------
108
sound_stream_update(sound_stream & stream,std::vector<read_stream_view> const & inputs,std::vector<write_stream_view> & outputs)109 void geebee_sound_device::sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs)
110 {
111 auto &buffer = outputs[0];
112
113 for (int sampindex = 0; sampindex < buffer.samples(); sampindex++)
114 {
115 buffer.put_int(sampindex, m_sound_signal, 32768);
116 /* 1V = HSYNC = 18.432MHz / 3 / 2 / 384 = 8000Hz */
117 {
118 m_vcount++;
119 /* noise clocked with raising edge of 2V */
120 if ((m_vcount & 3) == 2)
121 {
122 /* bit0 = bit0 ^ !bit10 */
123 if ((m_noise & 1) == ((m_noise >> 10) & 1))
124 m_noise = ((m_noise << 1) & 0xfffe) | 1;
125 else
126 m_noise = (m_noise << 1) & 0xfffe;
127 }
128 switch (m_sound_latch & 7)
129 {
130 case 0: /* 4V */
131 m_sound_signal = (m_vcount & 0x04) ? m_decay[m_volume] : 0;
132 break;
133 case 1: /* 8V */
134 m_sound_signal = (m_vcount & 0x08) ? m_decay[m_volume] : 0;
135 break;
136 case 2: /* 16V */
137 m_sound_signal = (m_vcount & 0x10) ? m_decay[m_volume] : 0;
138 break;
139 case 3: /* 32V */
140 m_sound_signal = (m_vcount & 0x20) ? m_decay[m_volume] : 0;
141 break;
142 case 4: /* TONE1 */
143 m_sound_signal = !(m_vcount & 0x01) && !(m_vcount & 0x10) ? m_decay[m_volume] : 0;
144 break;
145 case 5: /* TONE2 */
146 m_sound_signal = !(m_vcount & 0x02) && !(m_vcount & 0x20) ? m_decay[m_volume] : 0;
147 break;
148 case 6: /* TONE3 */
149 m_sound_signal = !(m_vcount & 0x04) && !(m_vcount & 0x40) ? m_decay[m_volume] : 0;
150 break;
151 default: /* NOISE */
152 /* QH of 74164 #4V */
153 m_sound_signal = (m_noise & 0x8000) ? m_decay[m_volume] : 0;
154 }
155
156 }
157 }
158 }
159