Experiments with WOZ writing

cardDisk2Sequencer.go

@@ -30,7 +30,7 @@ type CardDisk2Sequencer struct {
 	motorDelay uint64  // NE556 timer, used to delay motor off
 	drive      [2]cardDisk2SequencerDrive
 
-	lastPulse       bool
+	lastWriteValue  bool  // We write transitions to the WOZ file. We store the last value to send a pulse on change.
 	lastPulseCycles uint8 // There is a new pulse every 4ms, that's 8 cycles of 2Mhz
 
 	lastCycle uint64 // 2 Mhz cycles
@@ -110,8 +110,8 @@ func (c *CardDisk2Sequencer) catchUp(data uint8) {
 
 	motorOn := c.step(data, true)
 	if motorOn && currentCycle > c.lastCycle+disk2CyclestoLoseSsync {
-		// We have losy sync. We start the count.
-		//We do at least a couple 2 Mhz cycles
+		// We have lost sync. We start the count.
+		// We do at least a couple 2 Mhz cycles
 		c.lastCycle = currentCycle - 2
 	}
 	c.lastCycle++
@@ -187,6 +187,7 @@ func (c *CardDisk2Sequencer) step(data uint8, firstStep bool) bool {
 	pulse := false
 	c.lastPulseCycles++
 	if c.lastPulseCycles == disk2PulseCyles {
+		// Read
 		pulse = c.drive[0].readPulse() ||
 			c.drive[1].readPulse()
 		c.lastPulseCycles = 0
@@ -254,6 +255,15 @@ func (c *CardDisk2Sequencer) step(data uint8, firstStep bool) bool {
 			// Load
 			c.register = data
 		}
+
+		if c.q[7] && (inst&0x3) != 0 {
+			currentWriteValue := next >= 0x8
+			writePulse := currentWriteValue != c.lastWriteValue
+			c.drive[0].writePulse(writePulse)
+			c.drive[1].writePulse(writePulse)
+			c.lastWriteValue = currentWriteValue
+
+		}
 	}
 
 	//fmt.Printf("[D2SEQ] Step. seq:%x inst:%x next:%x reg:%02x\n",

cardDisk2SequencerDrive.go

@@ -66,12 +66,15 @@ func (d *cardDisk2SequencerDrive) readPulse() bool {
 	}
 
 	// Get next bit taking into account the MC3470 latency and weak bits
-	var fluxBit uint8
+	var fluxBit bool
 	fluxBit, d.position, d.positionMax = d.data.GetNextBitAndPosition(
 		d.position,
 		d.positionMax,
 		d.currentQuarterTrack)
-	d.mc3470Buffer = (d.mc3470Buffer<<1 + fluxBit) & 0x0f
+	d.mc3470Buffer = (d.mc3470Buffer << 1) & 0x0f
+	if fluxBit {
+		d.mc3470Buffer++
+	}
 	bit := ((d.mc3470Buffer >> 1) & 0x1) != 0 // Use the previous to last bit to add latency
 	if d.mc3470Buffer == 0 && rand.Intn(100) < 30 {
 		// Four consecutive zeros. It'a a fake bit.
@@ -82,6 +85,14 @@ func (d *cardDisk2SequencerDrive) readPulse() bool {
 	return bit
 }
 
-func (d *cardDisk2SequencerDrive) writePulse(value uint8) {
-	panic("Write not implemented on woz disk implementation")
+func (d *cardDisk2SequencerDrive) writePulse(value bool) {
+	if d.writeProtected || !d.enabled || d.data == nil {
+		return
+	}
+
+	d.data.SetBit(
+		value,
+		d.position,
+		d.positionMax,
+		d.currentQuarterTrack)
 }

storage/diskette.go

@@ -16,6 +16,7 @@ type Diskette interface {
 func IsDiskette(filename string) bool {
 	data, _, err := LoadResource(filename)
 	if err != nil {
+		panic(err)
 		return false
 	}
 

storage/disketteWoz.go

@@ -122,9 +122,12 @@ func (d *disketteWoz) Read(quarterTrack int, cycle uint64) uint8 {
 	// TODO: avoid processing too many bits if delta is big
 	for i := uint64(0); i < deltaBits; i++ {
 		// Get next bit taking into account the MC3470 latency and weak bits
-		var fluxBit uint8
+		var fluxBit bool
 		fluxBit, d.position, d.positionMax = d.data.GetNextBitAndPosition(d.position, d.positionMax, quarterTrack)
-		d.mc3470Buffer = (d.mc3470Buffer<<1 + fluxBit) & 0x0f
+		d.mc3470Buffer = (d.mc3470Buffer << 1) & 0x0f
+		if fluxBit {
+			d.mc3470Buffer++
+		}
 		bit := (d.mc3470Buffer >> 1) & 0x1 // Use the previous to last bit to add latency
 		if d.mc3470Buffer == 0 && rand.Intn(100) < 3 {
 			// Four consecutive zeros. It'a a fake bit.

storage/fileWoz.go

@@ -80,7 +80,7 @@ const (
 var headerWoz1 = []uint8{0x57, 0x4f, 0x5A, 0x31, 0xFF, 0x0A, 0x0D, 0x0A}
 var headerWoz2 = []uint8{0x57, 0x4f, 0x5A, 0x32, 0xFF, 0x0A, 0x0D, 0x0A}
 
-func (f *FileWoz) GetNextBitAndPosition(position uint32, positionMax uint32, quarterTrack int) (uint8, uint32, uint32) {
+func (f *FileWoz) GetNextBitAndPosition(position uint32, positionMax uint32, quarterTrack int) (bool, uint32, uint32) {
 	if positionMax == 0 {
 		// First unitialised use
 		positionMax = ^uint32(0) // MaxUint32
@@ -93,7 +93,7 @@ func (f *FileWoz) GetNextBitAndPosition(position uint32, positionMax uint32, qua
 	if trackIndex == 0xff {
 		// No track defined
 		// TODO: return random value
-		return 0, position, positionMax
+		return false, position, positionMax
 	}
 	trackWoz := f.tracks[trackIndex]
 
@@ -103,7 +103,28 @@ func (f *FileWoz) GetNextBitAndPosition(position uint32, positionMax uint32, qua
 		positionMax = trackWoz.bitCount
 	}
 
-	return trackWoz.data[position/8] >> (7 - position%8) & 1, position, positionMax
+	value := (trackWoz.data[position/8] >> (7 - position%8) & 1) == 1
+	return value, position, positionMax
+}
+
+func (f *FileWoz) SetBit(value bool, position uint32, positionMax uint32, quarterTrack int) {
+	// The position is not moved, GetNextBitAndPosition() would have been called previously.
+
+	trackIndex := f.trackMap[quarterTrack]
+	if trackIndex == 0xff {
+		// No track defined. Nothing is saved
+		return
+	}
+	trackWoz := f.tracks[trackIndex]
+
+	mask := uint8(1) << (7 - position%8)
+	if value {
+		trackWoz.data[position/8] |= mask
+	} else {
+		trackWoz.data[position/8] &= ^mask
+	}
+
+	fmt.Printf("Saving %v at %v\n", value, position)
 }
 
 func isFileWoz(data []uint8) bool {