Code cleanup/removal of cruft.

[thunder] / src / psg.cpp

diff --git a/src/psg.cpp b/src/psg.cpp
index b4f3f47c0f59da0724ac25583c921b0265d30716..5d6e6693101fabae7981911dd16dd0826e39600a 100644 (file)
--- a/src/psg.cpp
+++ b/src/psg.cpp
@@ -12,6 +12,12 @@
 // ---  ----------  -----------------------------------------------------------
 // JLH  04/21/2014  Created this file.
 //
+//
+// Notes:
+// ------
+// The emulator creates signed 16-bit samples. Make sure there's enough room in
+// your buffer for them!
+//
 
 #include "psg.h"
 #include <stdio.h>
@@ -33,20 +39,24 @@ static Voice voice[8];
 static uint8_t memory[0x200];
 //static 
 static uint32_t sampleRate = 44100;
-
-extern FILE * psg1;
-extern FILE * psg2;
+static uint32_t divisor;
 
 
 void InitPSG(uint32_t s/*=44100*/)
 {
        sampleRate = s;
+       divisor = (uint32_t)((float)s / 0.735); // Voodoo constant
 
+       // Noise generation will fail if the noise seeds aren't primed...
        for(int i=0; i<8; i++)
                voice[i].noiseSeed = 1;
 }
 
 
+//
+// Note that it doesn't wipe out the buffer passed in, if you want it wiped,
+// you have to wipe it yourself. :-)
+//
 void UpdatePSG(uint8_t * buffer, int count)
 {
 /*
@@ -54,8 +64,6 @@ 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;
 
@@ -74,7 +82,8 @@ if F == 22050, then counter += 0.5 for each sample.
 // 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 pos = (voice[i].counter / (65536)) & 0x1F;
+                               uint8_t pos = (voice[i].counter / divisor) & 0x1F;
                                uint8_t sample = ((pos & 0x01) == 0
                                        ? memory[(voice[i].waveform * 16) + (pos / 2)] >> 4
                                        : memory[(voice[i].waveform * 16) + (pos / 2)]) & 0x0F;
@@ -89,6 +98,10 @@ if F == 22050, then counter += 0.5 for each sample.
                        if ((voice[i].leftVolume == 0) || ((voice[i].frequency & 0xFF) == 0))
                                continue;
 
+                       // The hold stuff here is VOODOO
+                       // Need to figure out what's really going on here, what the clock
+                       // rate of this chip is. Also, some freqs can be > 255 according to
+                       // Rolling Thunder...
                        int16_t sample = (7 * voice[i].leftVolume) << 4;
                        int16_t noiseSign = 1;
                        int16_t hold = 1 << 1;
@@ -96,18 +109,6 @@ if F == 22050, then counter += 0.5 for each sample.
                        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)
                                {