PCE: Added LFO support

Core/PCE/PcePsg.cpp

@@ -14,6 +14,10 @@ PcePsg::PcePsg(Emulator* emu)
 	_soundBuffer = new int16_t[PcePsg::MaxSamples * 2];
 	memset(_soundBuffer, 0, PcePsg::MaxSamples * 2 * sizeof(int16_t));
 
+	for(int i = 0; i < 6; i++) {
+		_channels[i].Init(i, this);
+	}
+
 	_leftChannel = blip_new(PcePsg::MaxSamples);
 	_rightChannel = blip_new(PcePsg::MaxSamples);
 
@@ -31,6 +35,26 @@ PcePsg::~PcePsg()
 	delete[] _soundBuffer;
 }
 
+bool PcePsg::IsLfoEnabled()
+{
+	return (_state.LfoControl & 0x80) == 0 && (_state.LfoControl & 0x03);
+}
+
+uint16_t PcePsg::GetLfoFrequency()
+{
+	return _state.LfoFrequency ? _state.LfoFrequency : 0x100;
+}
+
+uint32_t PcePsg::GetLfoCh1PeriodOffset()
+{
+	//When LFO is enabled, the period of channel 1 is altered
+	//based on channel's 2 current output, multiplied by either 1, 4 or 16
+	//depending on the value in the lower 2 bits of the LFO's control register
+	int shift = ((_state.LfoControl & 0x03) - 1) * 2;
+	int8_t ch2Out = _channels[1].GetState().CurrentOutput;
+	return (uint32_t)(ch2Out << shift);
+}
+
 void PcePsg::Write(uint16_t addr, uint8_t value)
 {
 	Run();
@@ -57,7 +81,6 @@ void PcePsg::Write(uint16_t addr, uint8_t value)
 			}
 			break;
 
-		//TODO, LFO is not implemented
 		case 8: _state.LfoFrequency = value; break;
 		case 9: _state.LfoControl = value; break;
 	}

Core/PCE/PcePsg.h

@@ -33,6 +33,10 @@ public:
 	PcePsg(Emulator* emu);
 	~PcePsg();
 
+	bool IsLfoEnabled();
+	uint16_t GetLfoFrequency();
+	uint32_t GetLfoCh1PeriodOffset();
+
 	PcePsgState& GetState() { return _state; }
 	PcePsgChannelState& GetChannelState(uint8_t ch) { return _channels[ch].GetState(); }
 

Core/PCE/PcePsgChannel.cpp

@@ -1,5 +1,6 @@
 #include "stdafx.h"
-#include "PcePsgChannel.h"
+#include "PCE/PcePsgChannel.h"
+#include "PCE/PcePsg.h"
 
 PcePsgChannel::PcePsgChannel()
 {
@@ -8,7 +9,13 @@ PcePsgChannel::PcePsgChannel()
 	}
 }
 
-uint16_t PcePsgChannel::GetPeriod()
+void PcePsgChannel::Init(uint8_t index, PcePsg* psg)
+{
+	_chIndex = index;
+	_psg = psg;
+}
+
+uint32_t PcePsgChannel::GetPeriod()
 {
 	if(_state.DdaEnabled) {
 		return 0;
@@ -19,10 +26,22 @@ uint16_t PcePsgChannel::GetPeriod()
 			return ((~_state.NoiseFrequency) & 0x1F) * 128;
 		}
 	} else {
-		if(_state.Frequency == 0) {
-			return 0xFFF + 1;
+		uint32_t period = _state.Frequency;
+
+		if(_chIndex == 0 && _psg->IsLfoEnabled()) {
+			//When enabled, LFO alters channel 1's frequency/period
+			period = (period + _psg->GetLfoCh1PeriodOffset()) & 0xFFF;
 		}
-		return _state.Frequency;
+
+		period = period ? period : 0x1000;
+
+		if(_chIndex == 1 && _psg->IsLfoEnabled()) {
+			//When enabled, LFO acts as a clock divider for channel 2
+			//which reduces its frequency (increases its period)
+			period *= _psg->GetLfoFrequency();
+		}
+
+		return period;
 	}
 }
 
@@ -30,7 +49,7 @@ void PcePsgChannel::Run(uint32_t clocks)
 {
 	if(_state.Enabled) {
 		if(_state.DdaEnabled) {
-			_state.CurrentOutput = (int16_t)_state.DdaOutputValue - 0x10;
+			_state.CurrentOutput = (int8_t)_state.DdaOutputValue - 0x10;
 		} else {
 			_state.Timer -= clocks;
 
@@ -44,9 +63,9 @@ void PcePsgChannel::Run(uint32_t clocks)
 			}
 
 			if(_state.NoiseEnabled) {
-				_state.CurrentOutput = (int16_t)_noiseData[_noiseAddr] - 0x10;
+				_state.CurrentOutput = (int8_t)_noiseData[_noiseAddr] - 0x10;
 			} else {
-				_state.CurrentOutput = (int16_t)_state.WaveData[_state.ReadAddr] - 0x10;
+				_state.CurrentOutput = (int8_t)_state.WaveData[_state.ReadAddr] - 0x10;
 			}
 		}
 	} else {
@@ -65,7 +84,7 @@ int16_t PcePsgChannel::GetOutput(bool forLeftChannel, uint8_t masterVolume)
 		return 0;
 	}
 
-	return _state.CurrentOutput * volumeReduction[reductionFactor];
+	return (int16_t)_state.CurrentOutput * volumeReduction[reductionFactor];
 }
 
 uint16_t PcePsgChannel::GetTimer()

Core/PCE/PcePsgChannel.h

@@ -3,18 +3,24 @@
 #include "PCE/PceTypes.h"
 #include "Utilities/RandomHelper.h"
 
+class PcePsg;
+
 class PcePsgChannel
 {
 private:
 	PcePsgChannelState _state = {};
+	PcePsg* _psg = nullptr;
+	uint8_t _chIndex = 0;
 	uint8_t _noiseData[0x1000];
 	uint16_t _noiseAddr = 0;
 
-	uint16_t GetPeriod();
+	uint32_t GetPeriod();
 
 public:
 	PcePsgChannel();
 
+	void Init(uint8_t index, PcePsg* psg);
+
 	PcePsgChannelState& GetState() { return _state; }
 
 	void Run(uint32_t clocks);

Core/PCE/PceTypes.h

@@ -204,8 +204,8 @@ struct PcePsgChannelState
 
 	uint8_t WriteAddr;
 	uint8_t ReadAddr;
-	uint16_t Timer;
-	int16_t CurrentOutput;
+	uint32_t Timer;
+	int8_t CurrentOutput;
 
 	//Channel 5 & 6 only
 	bool NoiseEnabled;

NewUI/Interop/DebugState.cs

@@ -1449,8 +1449,8 @@ namespace Mesen.Interop
 
 		public byte WriteAddr;
 		public byte ReadAddr;
-		public UInt16 Timer;
-		public Int16 CurrentOutput;
+		public UInt32 Timer;
+		public byte CurrentOutput;
 
 		//Channel 5 & 6 only
 		[MarshalAs(UnmanagedType.I1)] public bool NoiseEnabled;