--- /dev/null
+//
+// PSG handler
+//
+// This emulates the Rolling Thunder PSG (Namco CUS30)
+//
+// by James Hammons
+// (C) 2014 Underground Software
+//
+// JLH = James Hammons <jlhamm@acm.org>
+//
+// Who When What
+// --- ---------- -----------------------------------------------------------
+// JLH 04/21/2014 Created this file.
+//
+
+#include "psg.h"
+#include <stdio.h>
+#include <string.h>
+
+
+struct Voice
+{
+ uint8_t leftVolume;
+ uint8_t rightVolume;
+ uint8_t waveform;
+ uint32_t frequency;
+ uint32_t counter;
+ bool noise;
+ uint32_t noiseSeed;
+};
+
+static Voice voice[8];
+static uint8_t memory[0x200];
+//static
+static uint32_t sampleRate = 44100;
+
+extern FILE * psg1;
+extern FILE * psg2;
+
+
+void InitPSG(uint32_t s/*=44100*/)
+{
+ sampleRate = s;
+
+ for(int i=0; i<8; i++)
+ voice[i].noiseSeed = 1;
+}
+
+
+void UpdatePSG(uint8_t * buffer, int count)
+{
+/*
+if F == 44100, then counter++ for each sample.
+if F == 88200, then counter += 2 for each sample.
+if F == 22050, then counter += 0.5 for each sample.
+*/
+// memset(buffer, 0, count * 2);
+
+ // Recast buffer as int16, we're doing 16-bit sound here
+ int16_t * p = (int16_t *)buffer;
+
+ for(int i=0; i<8; i++)
+ {
+ if (!voice[i].noise)
+ {
+ if ((voice[i].leftVolume == 0) || (voice[i].frequency == 0))
+ continue;
+
+ for(int j=0; j<count; j++)
+ {
+// uint8_t pos = (voice[i].counter / (sampleRate * 2)) & 0x1F;
+// Where does 60000 come from? IDK. This would probably change depending on
+// the playback rate (currently, 44100). N.B.: 58800 is a hair too high in pitch!
+// 44100 / 60000 = 0.735
+// 192000 / 60000 = 3.2
+// uint8_t pos = (voice[i].counter / (60000)) & 0x1F;
+ uint8_t pos = (voice[i].counter / (65536)) & 0x1F;
+ uint8_t sample = ((pos & 0x01) == 0
+ ? memory[(voice[i].waveform * 16) + (pos / 2)] >> 4
+ : memory[(voice[i].waveform * 16) + (pos / 2)]) & 0x0F;
+// p[j] += (((memory[(voice[i].waveform * 32) + pos] & 0x0F) - 8)
+// * voice[i].leftVolume) << 5;
+ p[j] += ((sample - 8) * voice[i].leftVolume) << 5;
+ voice[i].counter += voice[i].frequency;
+ }
+ }
+ else
+ {
+ if ((voice[i].leftVolume == 0) || ((voice[i].frequency & 0xFF) == 0))
+ continue;
+
+ int16_t sample = (7 * voice[i].leftVolume) << 4;
+ int16_t noiseSign = 1;
+ int16_t hold = 1 << 1;
+
+ for(int j=0; j<count; j++)
+ {
+ p[j] += sample * noiseSign;
+#if 0
+if (i == 1)
+{
+ fputc(sample & 0xFF, psg1);
+ fputc((sample >> 8) & 0xFF , psg1);
+}
+else if (i == 3)
+{
+ fputc(sample & 0xFF, psg2);
+ fputc((sample >> 8) & 0xFF , psg2);
+}
+#endif
+
+ if (hold)
+ {
+ hold--;
+ continue;
+ }
+
+ hold = 1 << 1;
+
+ voice[i].counter += (voice[i].frequency & 0xFF) << 4;
+ int c = voice[i].counter >> 12;
+ voice[i].counter &= 0xFFF;
+
+ for(; c>0; c--)
+ {
+ if ((voice[i].noiseSeed + 1) & 0x02)
+ noiseSign *= -1;
+
+ if (voice[i].noiseSeed & 0x01)
+ voice[i].noiseSeed ^= 0x28000;
+
+ voice[i].noiseSeed >>= 1;
+ }
+ }
+ }
+ }
+}
+
+
+void WritePSG(uint16_t address, uint8_t data)
+{
+ if ((address >= 0x100) && (address <= 0x13F))
+ {
+ uint8_t channel = (address - 0x100) / 8;
+ uint8_t knob = (address - 0x100) - (channel * 8);
+
+ if (channel < 8)
+ {
+ switch (knob)
+ {
+ case 0:
+ voice[channel].leftVolume = data & 0x0F;
+ break;
+ case 1:
+ voice[channel].waveform = data >> 4;
+ voice[channel].frequency = ((data & 0x0F) << 16)
+ | (voice[channel].frequency & 0x0FFFF);
+#if 0
+printf("PSG: Setting waveform on channel %i to %i...\n", channel, voice[channel].waveform);
+#endif
+ break;
+ case 2:
+ voice[channel].frequency = (data << 8)
+ | (voice[channel].frequency & 0xF00FF);
+ break;
+ case 3:
+ voice[channel].frequency = data
+ | (voice[channel].frequency & 0xFFF00);
+ break;
+ case 4:
+ voice[channel].rightVolume = data & 0x0F;
+ // Noise switch is channel # + 1 (wraps to zero)
+ voice[(channel + 1) & 0x07].noise = (data & 0x80 ? true : false);
+#if 0
+if (voice[(channel + 1) & 0x07].noise)
+{
+ uint8_t ch = (channel + 1) & 0x07;
+ printf("PSG: Setting noise on channel %i, vol=%i, freq=%i...\n", ch, voice[ch].leftVolume, voice[ch].frequency);
+}
+#endif
+#if 0
+if (data & 0x0F)
+{
+ printf("PSG: Setting right volume on channel %i: vol=%i...\n", channel, voice[channel].rightVolume);
+}
+#endif
+ break;
+ }
+ }
+
+// return;
+ }
+#if 0
+ else
+ printf("PSG: Write to $%03X of $%02X...\n", address, data);
+#endif
+
+//if (address < 0x100)
+// printf("PSG: Waveform byte[$%02X] = $%02X...\n", address, data);
+
+ memory[address & 0x01FF] = data;
+}
+
+
+uint8_t ReadPSG(uint16_t address)
+{
+ return memory[address & 0x01FF];
+}
+
projects / thunder / blobdiff