fix

pkg/gba/apu.go

@@ -1,5 +1,19 @@
 package gba
 
+import (
+	"mettaur/pkg/ram"
+	"mettaur/pkg/util"
+)
+
+const (
+	SND_FREQUENCY         = 32768
+	SAMPLE_TIME   float64 = 1.0 / 32768
+)
+
+const (
+	CH_LEN = 1 << 14
+)
+
 const (
 	PSG_MAX = 0x7f
 	PSG_MIN = -0x80
@@ -13,6 +27,131 @@ const (
 var dutyLookUp = [4]float64{0.125, 0.25, 0.5, 0.75}
 var dutyLookUpi = [4]float64{0.875, 0.75, 0.5, 0.25}
 
-func (g *GBA) squareSample(ch int) {
-	// cntx := g._getRAM()
+type SoundChan struct {
+	phase      bool
+	lfsr       uint16
+	samples    float64
+	lengthTime float64
+	sweepTime  float64
+	envTime    float64
+}
+
+func (g *GBA) squareSample(ch int) int8 {
+	cntx := g._getRAM(ram.SOUNDCNT_X)
+	if !util.Bit(cntx, ch) {
+		return 0
+	}
+	if !(ch == 0 || ch == 1) {
+		return 0
+	}
+
+	toneAddr := uint32(ram.SOUND1CNT_H)
+	if ch == 1 {
+		toneAddr = ram.SOUND2CNT_L
+	}
+
+	freqHz := g._getRAM(ram.SOUND1CNT_X) & 0b0111_1111_1111
+	if ch == 1 {
+		freqHz = g._getRAM(ram.SOUND2CNT_H) & 0b0111_1111_1111
+	}
+	frequency := 131072 / float64(2048-freqHz)
+
+	// Full length of the generated wave (if enabled) in seconds
+	soundLen := g._getRAM(toneAddr) & 0b0011_1111
+	length := float64(64-soundLen) / 256
+
+	// Envelope volume change interval in seconds
+	envStep := g._getRAM(toneAddr) >> 8 & 0b111
+	envelopeInterval := float64(envStep) / 64
+
+	cycleSamples := SND_FREQUENCY / frequency // Numbers of samples that a single cycle (wave phase change 1 -> 0) takes at output sample rate
+
+	// Length reached check (if so, just disable the channel and return silence)
+	if (ch == 0 && util.Bit(g._getRAM(ram.SOUND1CNT_X), 14)) || (ch == 1 && util.Bit(g._getRAM(ram.SOUND2CNT_H), 14)) {
+		g.apu[ch].lengthTime += SAMPLE_TIME
+		if g.apu[ch].lengthTime >= length {
+			g.disableSoundChan(ch)
+			return 0
+		}
+	}
+
+	// Frequency sweep (Square 1 channel only)
+	sweepTime := (g._getRAM(ram.SOUND1CNT_L) >> 4) & 0b111
+	sweepInterval := 0.0078 * float64(sweepTime+1) // Frquency sweep change interval in seconds
+	if ch == 0 {
+		g.apu[0].sweepTime += SAMPLE_TIME
+		if g.apu[0].sweepTime >= sweepInterval {
+			g.apu[0].sweepTime -= sweepInterval
+			sweepShift := byte(g._getRAM(ram.SOUND1CNT_L) & 0b111)
+			if sweepShift > 0 {
+				disp := uint32(freqHz >> sweepShift)
+				if !util.Bit(g._getRAM(ram.SOUND1CNT_L), 3) {
+					freqHz += disp
+				} else {
+					freqHz -= disp
+				}
+
+				if freqHz < 0x7ff {
+					// update frequency
+					ctrl := uint16(g._getRAM(ram.SOUND1CNT_X))
+					ctrl = (ctrl & ^uint16(0x7ff)) | uint16(freqHz)
+					g._setRAM16(ram.SOUND1CNT_X, ctrl)
+				} else {
+					g.disableSoundChan(0)
+				}
+			}
+		}
+	}
+
+	envelope := uint16((g._getRAM(toneAddr) >> 12) & 0xf)
+	if envStep > 0 {
+		g.apu[ch].envTime += SAMPLE_TIME
+		if g.apu[ch].envTime >= envelopeInterval {
+			g.apu[ch].envTime -= envelopeInterval
+
+			tone := uint16(g._getRAM(toneAddr))
+			if util.Bit(tone, 11) {
+				if envelope < 0xf {
+					envelope++
+				}
+			} else {
+				if envelope > 0 {
+					envelope--
+				}
+			}
+
+			tone = (tone & ^uint16(0xf000)) | (envelope << 12)
+			g._setRAM16(toneAddr, tone)
+		}
+	}
+
+	// Phase change (when the wave goes from Low to High or High to Low, the Square Wave pattern)
+	duty := (g._getRAM(toneAddr) >> 6) & 0b111
+	g.apu[ch].samples++
+	if g.apu[ch].phase {
+		// 1 -> 0
+		phaseChange := cycleSamples * dutyLookUp[duty]
+		if g.apu[ch].samples > phaseChange {
+			g.apu[ch].samples -= phaseChange
+			g.apu[ch].phase = false
+		}
+	} else {
+		// 0 -> 1
+		phaseChange := cycleSamples * dutyLookUpi[duty]
+		if g.apu[ch].samples > phaseChange {
+			g.apu[ch].samples -= phaseChange
+			g.apu[ch].phase = true
+		}
+	}
+
+	if g.apu[ch].phase {
+		return int8((float64(envelope) / 15) * PSG_MAX)
+	}
+	return int8((float64(envelope) / 15) * PSG_MIN)
+}
+
+func (g *GBA) disableSoundChan(ch int) {
+	cntx := byte(g._getRAM(ram.SOUNDCNT_X))
+	cntx = cntx & ^(1 << ch)
+	g._setRAM8(ram.SOUNDCNT_X, cntx)
 }

pkg/gba/gba.go

@@ -57,6 +57,7 @@ type GBA struct {
 	dma        [4]*DMA
 	joypad     joypad.Joypad
 	DoSav      bool
+	apu        [4]*SoundChan
 }
 
 type Pipe struct {

pkg/ram/io.go

@@ -43,6 +43,27 @@ const (
 	BLDY     = base + 0x54
 )
 
+// Sound IO
+const (
+	SOUND1CNT_L = base + 0x60
+	SOUND1CNT_H = base + 0x62
+	SOUND1CNT_X = base + 0x64
+	SOUND2CNT_L = base + 0x68
+	SOUND2CNT_H = base + 0x6c
+	SOUND3CNT_L = base + 0x70
+	SOUND3CNT_H = base + 0x72
+	SOUND3CNT_X = base + 0x74
+	SOUND4CNT_L = base + 0x78
+	SOUND4CNT_H = base + 0x7c
+	SOUNDCNT_L  = base + 0x80
+	SOUNDCNT_H  = base + 0x82
+	SOUNDCNT_X  = base + 0x84
+	SOUNDBIAS   = base + 0x88
+	WAVE_RAM    = base + 0x90
+	FIFO_A      = base + 0xa0
+	FIFO_B      = base + 0xa4
+)
+
 // DMA Transfer
 const (
 	DMA0SAD = base + 0xb0