From d9f076ef642031403165dd5f2f4b3435c447fb05 Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Sat, 15 May 2021 14:18:16 -0500
Subject: [PATCH] prepare to add SMS platform

plays but no macro yet
---
 CMakeLists.txt                        |  1 +
 src/engine/engine.cpp                 |  4 ++
 src/engine/platform/sms.cpp           | 74 +++++++++++++++++++++++++++
 src/engine/platform/sms.h             | 21 ++++++++
 src/engine/platform/sound/sn76496.cpp |  2 +-
 src/engine/playback.cpp               |  9 ++++
 6 files changed, 110 insertions(+), 1 deletion(-)
 create mode 100644 src/engine/platform/sms.cpp
 create mode 100644 src/engine/platform/sms.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bb7105023..8d90ccdfc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -33,6 +33,7 @@ src/engine/engine.cpp
 src/engine/playback.cpp
 src/engine/platform/abstract.cpp
 src/engine/platform/genesis.cpp
+src/engine/platform/sms.cpp
 src/engine/platform/dummy.cpp)
 
 #imgui/imgui.cpp
diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index 016ba75a6..ef8e80f5b 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -3,6 +3,7 @@
 #include "../ta-log.h"
 #include "../audio/sdl.h"
 #include "platform/genesis.h"
+#include "platform/sms.h"
 #include "platform/dummy.h"
 #include <math.h>
 #include <zlib.h>
@@ -671,6 +672,9 @@ bool DivEngine::init() {
     case DIV_SYSTEM_GENESIS:
       dispatch=new DivPlatformGenesis;
       break;
+    case DIV_SYSTEM_SMS:
+      dispatch=new DivPlatformSMS;
+      break;
     default:
       dispatch=new DivPlatformDummy;
       break;
diff --git a/src/engine/platform/sms.cpp b/src/engine/platform/sms.cpp
new file mode 100644
index 000000000..ea486c36c
--- /dev/null
+++ b/src/engine/platform/sms.cpp
@@ -0,0 +1,74 @@
+#include "sms.h"
+#include <math.h>
+
+void DivPlatformSMS::acquire(short& l, short& r) {
+  short v;
+  sn->sound_stream_update(&v,1);
+  l=v;
+  r=v;
+}
+
+void DivPlatformSMS::tick() {
+  for (int i=0; i<3; i++) {
+    if (chan[i].freqChanged) {
+      sn->write(0x80|i<<5|(chan[i].freq&15));
+      sn->write(chan[i].freq>>4);
+      chan[i].freqChanged=false;
+    }
+  }
+  if (chan[3].freqChanged || updateSNMode) {
+    updateSNMode=false;
+    chan[3].freqChanged=false;
+    if (snNoiseMode&2) { // take period from channel 3
+      if (snNoiseMode&1) {
+        sn->write(0xe7);
+      } else {
+        sn->write(0xe3);
+      }
+      sn->write(0xdf);
+      sn->write(0xc0|(chan[3].freq&15));
+      sn->write(chan[3].freq>>4);
+    } else { // 3 fixed values
+      unsigned char value=chan[3].note%12;
+      if (value>2) value=2;
+      value=2-value;
+      sn->write(0xe0|value|((snNoiseMode&1)<<2));
+    }
+  }
+}
+
+int DivPlatformSMS::dispatch(DivCommand c) {
+  switch (c.cmd) {
+    case DIV_CMD_NOTE_ON:
+      chan[c.chan].freq=3430/pow(2.0f,((float)c.value/12.0f));
+      chan[c.chan].freqChanged=true;
+      chan[c.chan].note=c.value;
+      chan[c.chan].active=true;
+      sn->write(0x90|c.chan<<5|(15-chan[c.chan].vol));
+      break;
+    case DIV_CMD_NOTE_OFF:
+      chan[c.chan].active=false;
+      break;
+    case DIV_CMD_VOLUME:
+      chan[c.chan].vol=c.value;
+      sn->write(0x90|c.chan<<5|(15-chan[c.chan].vol));
+      break;
+    case DIV_CMD_STD_NOISE_MODE:
+      snNoiseMode=(c.value&1)|((c.value&16)>>3);
+      updateSNMode=true;
+      break;
+    default:
+      break;
+  }
+  return 1;
+}
+
+int DivPlatformSMS::init(DivEngine* p, int channels, int sugRate) {
+  parent=p;
+  rate=223722;
+  sn=new sn76496_device("sn",223722);
+  sn->device_start();
+  snNoiseMode=0;
+  updateSNMode=false;
+  return 4;
+}
diff --git a/src/engine/platform/sms.h b/src/engine/platform/sms.h
new file mode 100644
index 000000000..a8ef61d5e
--- /dev/null
+++ b/src/engine/platform/sms.h
@@ -0,0 +1,21 @@
+#include "../dispatch.h"
+#include "sound/sn76496.h"
+
+class DivPlatformSMS: public DivDispatch {
+  struct Channel {
+    int freq, baseFreq, pitch;
+    unsigned char ins, note;
+    bool active, insChanged, freqChanged, keyOn, keyOff;
+    signed char vol;
+    Channel(): freq(0), baseFreq(0), pitch(0), ins(0), note(0), active(false), insChanged(true), freqChanged(false), keyOn(false), keyOff(false), vol(15) {}
+  };
+  Channel chan[4];
+  unsigned char snNoiseMode;
+  bool updateSNMode;
+  sn76496_device* sn;
+  public:
+    void acquire(short& l, short& r);
+    int dispatch(DivCommand c);
+    void tick();
+    int init(DivEngine* parent, int channels, int sugRate);
+};
diff --git a/src/engine/platform/sound/sn76496.cpp b/src/engine/platform/sound/sn76496.cpp
index ef578b0a5..5e876c38b 100644
--- a/src/engine/platform/sound/sn76496.cpp
+++ b/src/engine/platform/sound/sn76496.cpp
@@ -165,7 +165,7 @@ sn76496_base_device::sn76496_base_device(
 }
 
 sn76496_device::sn76496_device(const char *tag, uint32_t clock)
-	: sn76496_base_device(tag, 0x10000, 0x04, 0x08, false, 8, false, true, clock)
+	: sn76496_base_device(tag, 0x8000, 0x01, 0x08, true, 1, false, false, clock)
 {
 }
 
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index 2e3fa62ed..6fcaa530b 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -33,6 +33,15 @@ bool DivEngine::perSystemEffect(int ch, unsigned char effect, unsigned char effe
           return false;
       }
       break;
+    case DIV_SYSTEM_SMS:
+      switch (effect) {
+        case 0x20: // SN noise mode
+          dispatch->dispatch(DivCommand(DIV_CMD_STD_NOISE_MODE,ch,effectVal));
+          break;
+        default:
+          return false;
+      }
+      break;
     default:
       return false;
   }