Nuked OPN2: ASIC YM3438 & YM2612 emulation

core/sound/sound.c

@@ -67,9 +67,14 @@ static int ym3438_accm[24][2];
 static int ym3438_sample[2];
 static unsigned int ym3438_cycles;
 
+void sound_ym3438_set_type(uint8 type)
+{
+  OPN2_SetChipType(&ym3438, type);
+}
+
 void YM3438_Reset(void)
 {
-  OPN2_Reset(&ym3438);
+  OPN2_Reset(&ym3438, config.ym3438_type);
 }
 
 void YM3438_Update(int *buffer, int length)
@@ -89,8 +94,8 @@ void YM3438_Update(int *buffer, int length)
         ym3438_sample[1] += ym3438_accm[j][1];
       }
     }
-    *buffer++ = ym3438_sample[0] * 8;
-    *buffer++ = ym3438_sample[1] * 8;
+    *buffer++ = ym3438_sample[0] * 11;
+    *buffer++ = ym3438_sample[1] * 11;
   }
 }
 

core/sound/sound.h

@@ -41,6 +41,9 @@
 #define _SOUND_H_
 
 /* Function prototypes */
+#ifdef HAVE_YM3438_CORE
+extern void sound_ym3438_set_type(uint8 type);
+#endif
 extern void sound_init(void);
 extern void sound_reset(void);
 extern int sound_context_save(uint8 *state);

core/sound/ym3438.c

@@ -39,7 +39,7 @@
  *      OPLx decapsulated(Matthew Gambrell, Olli Niemitalo):
  *          OPL2 ROMs.
  *
- * version: 1.0.5
+ * version: 1.0.6
  */
 
 #include <string.h>
@@ -966,6 +966,8 @@ void OPN2_ChOutput(ym3438_t *chip)
     Bit32u channel = chip->channel;
     Bit32u test_dac = chip->mode_test_2c[5];
     Bit16s out;
+    Bit16s sign;
+    Bit32u out_en;
     chip->ch_read = chip->ch_lock;
     if (chip->slot < 12)
     {
@@ -995,14 +997,54 @@ void OPN2_ChOutput(ym3438_t *chip)
     }
     chip->mol = 0;
     chip->mor = 0;
-    if (chip->ch_lock_l)
+
+    if (chip->chip_type == ym3438_type_ym2612)
+    {
+        out_en = ((chip->cycles & 3) == 3) || test_dac;
+        /* YM2612 DAC emulation(not verified) */
+        sign = out >> 8;
+        if (out >= 0)
+        {
+            out++;
+            sign++;
+        }
+        if (chip->ch_lock_l && out_en)
         {
             chip->mol = out;
         }
-    if (chip->ch_lock_r)
+        else
+        {
+            chip->mol = sign;
+        }
+        if (chip->ch_lock_r && out_en)
         {
             chip->mor = out;
         }
+        else
+        {
+            chip->mor = sign;
+        }
+        /* Amplify signal */
+        chip->mol *= 3;
+        chip->mor *= 3;
+    }
+    else
+    {
+        out_en = ((chip->cycles & 3) != 0) || test_dac;
+        /* Discrete YM3438 seems has the ladder effect too */
+        if (out >= 0 && chip->chip_type == ym3438_type_discrete)
+        {
+            out++;
+        }
+        if (chip->ch_lock_l && out_en)
+        {
+            chip->mol = out;
+        }
+        if (chip->ch_lock_r && out_en)
+        {
+            chip->mor = out;
+        }
+    }
 }
 
 void OPN2_FMGenerate(ym3438_t *chip)
@@ -1161,7 +1203,7 @@ void OPN2_KeyOn(ym3438_t*chip)
     }
 }
 
-void OPN2_Reset(ym3438_t *chip)
+void OPN2_Reset(ym3438_t *chip, Bit32u type)
 {
     Bit32u i;
     memset(chip, 0, sizeof(ym3438_t));
@@ -1177,6 +1219,12 @@ void OPN2_Reset(ym3438_t *chip)
         chip->pan_l[i] = 1;
         chip->pan_r[i] = 1;
     }
+    chip->chip_type = type;
+}
+
+void OPN2_SetChipType(ym3438_t *chip, Bit32u type)
+{
+    chip->chip_type = type;
 }
 
 void OPN2_Clock(ym3438_t *chip, Bit32u *buffer)
@@ -1350,7 +1398,7 @@ Bit32u OPN2_ReadIRQPin(ym3438_t *chip)
 
 Bit8u OPN2_Read(ym3438_t *chip, Bit32u port)
 {
-    if ((port & 3) == 0)
+    if ((port & 3) == 0 || chip->chip_type == ym3438_type_asic)
     {
         if (chip->mode_test_21[6])
         {

core/sound/ym3438.h

@@ -45,6 +45,12 @@
 #ifndef YM3438_H
 #define YM3438_H
 
+enum {
+    ym3438_type_discrete = 0,   /* Discrete YM3438 (Teradrive)          */
+    ym3438_type_asic = 1,       /* ASIC YM3438 (MD1 VA7, MD2, MD3, etc) */
+    ym3438_type_ym2612 = 2      /* YM2612 (MD1, MD2 VA2)                */
+};
+
 #include <stdint.h>
 
 typedef uintptr_t       Bitu;
@@ -60,6 +66,7 @@ typedef int8_t          Bit8s;
 
 typedef struct
 {
+    Bit32u chip_type;
     Bit32u cycles;
     Bit32u slot;
     Bit32u channel;
@@ -201,7 +208,8 @@ typedef struct
     Bit8u pms[6];
 } ym3438_t;
 
-void OPN2_Reset(ym3438_t *chip);
+void OPN2_Reset(ym3438_t *chip, Bit32u type);
+void OPN2_SetChipType(ym3438_t *chip, Bit32u type);
 void OPN2_Clock(ym3438_t *chip, Bit32u *buffer);
 void OPN2_Write(ym3438_t *chip, Bit32u port, Bit8u data);
 void OPN2_SetTestPin(ym3438_t *chip, Bit32u value);

libretro/libretro.c

@@ -1117,6 +1117,18 @@ static void check_variables(void)
       sound_reset();
     }
   }
+  var.key = "genesis_plus_gx_ym3438_type";
+  environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var);
+  {
+    if (!strcmp(var.value, "ym2612"))
+      config.ym3438_type = ym3438_type_ym2612;
+    else if (!strcmp(var.value, "ym3438 asic"))
+      config.ym3438_type = ym3438_type_asic;
+    else
+      config.ym3438_type = ym3438_type_discrete;
+
+    sound_ym3438_set_type(config.ym3438_type);
+  }
   #endif
 
   var.key = "genesis_plus_gx_blargg_ntsc_filter";
@@ -1657,6 +1669,7 @@ void retro_set_environment(retro_environment_t cb)
       { "genesis_plus_gx_dac_bits", "YM2612 DAC quantization; disabled|enabled" },
       #ifdef HAVE_YM3438_CORE
       { "genesis_plus_gx_ym3438", "YM2612/YM3438 core; mame|nuked opn2" },
+      { "genesis_plus_gx_ym3438_type", "YM2612/YM3438 type(Nuked OPN2); ym2612|ym3438 asic|ym3438 discrete" },
       #endif
 
       { "genesis_plus_gx_audio_filter", "Audio filter; disabled|low-pass" },

libretro/osd.h

@@ -93,6 +93,7 @@ struct
   uint8 ym2413;
 #ifdef HAVE_YM3438_CORE
   uint8 ym3438;
+  uint8 ym3438_type;
 #endif
   uint8 mono;
   int16 psg_preamp;