// license:BSD-3-Clause // copyright-holders:Jonathan Gevaryahu /*************************************************************************** audio/socrates.c Copyright (C) 2010-2011 Jonathan Gevaryahu AKA Lord Nightmare This handles the two squarewaves (plus the one weird wave) channels on the V-tech Socrates system 27-0769 ASIC. ****************************************************************************/ #include "emu.h" #include "socrates.h" // device type definition DEFINE_DEVICE_TYPE(SOCRATES_SOUND, socrates_snd_device, "socrates_snd", "Socrates Sound") //------------------------------------------------- // socrates_snd_device - constructor //------------------------------------------------- socrates_snd_device::socrates_snd_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) : device_t(mconfig, SOCRATES_SOUND, tag, owner, clock) , device_sound_interface(mconfig, *this) { } //------------------------------------------------- // device_start - device-specific startup //------------------------------------------------- void socrates_snd_device::device_start() { m_freq[0] = m_freq[1] = 0xff; /* channel 1,2 frequency */ m_vol[0] = m_vol[1] = 0x07; /* channel 1,2 volume */ m_enable[0] = m_enable[1] = 0x01; /* channel 1,2 enable */ m_channel3 = 0x00; /* channel 3 weird register */ m_DAC_output = 0x00; /* output */ m_state[0] = m_state[1] = m_state[2] = 0; m_accum[0] = m_accum[1] = m_accum[2] = 0xFF; m_stream = machine().sound().stream_alloc(*this, 0, 1, clock() ? clock() : machine().sample_rate()); } //------------------------------------------------- // sound_stream_update - handle a stream update //------------------------------------------------- void socrates_snd_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples) { for (int i = 0; i < samples; i++) { snd_clock(); outputs[0][i] = ((int)m_DAC_output<<4); } } const uint8_t socrates_snd_device::s_volumeLUT[16] = { 0, 61, 100, 132, 158, 183, 201, 218, 233, 242, 253, 255, 250, 240, 224, 211 }; // this table is actually quite weird on the real console. // 0, 0.033, 0.055, 0.07175, 0.086, 0.1, 0.11, 0.119, 0.127, 0.132, 0.138, 0.139, 0.136, 0.131, 0.122, 0.115 are the voltage amplitudes for the steps on channel 2. the last four are particularly bizarre, probably caused by some sort of internal clipping. void socrates_snd_device::snd_clock() /* called once per clock */ { for (int channel = 0; channel < 2; channel++) { if ((m_accum[channel] == 0) && m_enable[channel]) { m_state[channel] = (m_state[channel]^0x1); m_accum[channel] = m_freq[channel]; } else if (m_enable[channel]) { m_accum[channel]--; } else { m_accum[channel] = 0; // channel is disabled m_state[channel] = 0; } } // handle channel 3 here m_DAC_output = (m_state[0]?(s_volumeLUT[m_vol[0]]*9.4):0); // channel 1 is ~2.4 times as loud as channel 2 m_DAC_output += (m_state[1]?(s_volumeLUT[m_vol[1]]<<2):0); // add channel 3 to dac output here } void socrates_snd_device::reg0_w(int data) { m_stream->update(); m_freq[0] = data; } void socrates_snd_device::reg1_w(int data) { m_stream->update(); m_freq[1] = data; } void socrates_snd_device::reg2_w(int data) { m_stream->update(); m_vol[0] = data&0xF; m_enable[0] = (data&0x10)>>4; } void socrates_snd_device::reg3_w(int data) { m_stream->update(); m_vol[1] = data&0xF; m_enable[1] = (data&0x10)>>4; } void socrates_snd_device::reg4_w(int data) { m_stream->update(); m_channel3 = data; }