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izapple2
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Better comments on the stepper motor code

This commit is contained in:
Ivan Izaguirre 2019-12-02 22:43:40 +01:00 committed by Iván Izaguirre
parent 212ed2a90a
commit 9ad13ae483
1 changed files with 54 additions and 48 deletions
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102
cardDisk2.go
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@ -36,7 +36,7 @@ type cardDisk2Drive struct {
diskette *diskette16sector
power bool // q4, not realy used for anything
position int
magnets uint8 // q3, q2, q1 and q0 with q0 on the LSB
phases uint8 // q3, q2, q1 and q0 with q0 on the LSB. Magnets that are active on the stepper motor
tracksStep int // Stepmotor for tracks position. 4 steps per track
}
@ -63,8 +63,8 @@ func (c *cardDisk2) assign(a *Apple2, slot int) {
c.addCardSoftSwitchR(phase<<1, func(_ *ioC0Page) uint8 {
// Update magnets and position
drive := &c.drive[c.selected]
drive.magnets &^= (1 << phase)
drive.tracksStep = moveStep(drive.magnets, drive.tracksStep)
drive.phases &^= (1 << phase)
drive.tracksStep = moveStep(drive.phases, drive.tracksStep)
return c.dataLatch // All even addresses return the last dataLatch
}, fmt.Sprintf("PHASE%vOFF", phase))
@ -72,8 +72,8 @@ func (c *cardDisk2) assign(a *Apple2, slot int) {
c.addCardSoftSwitchR((phase<<1)+1, func(_ *ioC0Page) uint8 {
// Update magnets and position
drive := &c.drive[c.selected]
drive.magnets |= (1 << phase)
drive.tracksStep = moveStep(drive.magnets, drive.tracksStep)
drive.phases |= (1 << phase)
drive.tracksStep = moveStep(drive.phases, drive.tracksStep)
return 0
}, fmt.Sprintf("PHASE%vOFF", phase))
@ -119,56 +119,62 @@ func (c *cardDisk2) assign(a *Apple2, slot int) {
c.cardBase.assign(a, slot)
}
/*
Stepper motor to position the track.
There are a number of group of four magnets. The stepper motor can be thought as a long
line of groups of magnets, each group on the same configuration. We call phase each of those
magnets. The cog is attracted to the enabled magnets, and can stay aligned to a magnet or
between two.
Phases (magents): 3 2 1 0 3 2 1 0 3 2 1 0
Cog direction (step withn a group): 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
We will consider that the cog would go to the prefferred postion if there is one. Independenly
of the previous position. The previous position is only used to know if it goes up or down
a full group.
*/
const (
maxStep = 68 * 2 // What is the maximum quarter tracks a DiskII can go?
stepsPerTurn = 8
)
const (
dirN = 0
dirNW = 1
dirW = 2
dirSW = 3
dirS = 4
dirSE = 5
dirE = 6
dirNE = 7
dirUndefined = 8
undefinedPosition = -1
maxStep = 68 * 2 // What is the maximum quarter tracks a DiskII can go?
stepsPerGroup = 8
stepsPerTrack = 4
)
var magnetsDirections = []int{
// Magnets bits, ESWN: east, south, west, north
dirUndefined, // 0000
dirN, // 0001
dirW, // 0010
dirNW, // 0011
dirS, // 0100
dirUndefined, // 0101
dirSW, // 0110
dirW, // 0111
dirE, // 1000
dirNE, // 1001
dirUndefined, // 1010
dirN, // 1011
dirSE, // 1100
dirE, // 1101
dirS, // 1110
dirUndefined, // 1111
var cogPositions = []int{
undefinedPosition, // 0000, phases active
0, // 0001
2, // 0010
1, // 0011
4, // 0100
undefinedPosition, // 0101
3, // 0110
2, // 0111
6, // 1000
7, // 1001
undefinedPosition, // 1010
0, // 1011
5, // 1100
6, // 1101
4, // 1110
undefinedPosition, // 1111
}
func moveStep(magnets uint8, prevStep int) int {
func moveStep(phases uint8, prevStep int) int {
//fmt.Printf("magnets: 0x%x\n", magnets)
//fmt.Printf("magnets: 0x%x\n", phases)
magnetsDirection := magnetsDirections[magnets]
if magnetsDirection == dirUndefined {
cogPosition := cogPositions[phases]
if cogPosition == undefinedPosition {
// Don't move if magnets don't push on a defined direction.
return prevStep
}
prevDirection := prevStep % stepsPerTurn // Direction, removing full revolutions.
delta := magnetsDirection - prevDirection
prevPosition := prevStep % stepsPerGroup // Direction, step in the current group of magnets.
delta := cogPosition - prevPosition
if delta < 0 {
delta = delta + stepsPerTurn
delta = delta + stepsPerGroup
}
var nextStep int
@ -183,7 +189,7 @@ func moveStep(magnets uint8, prevStep int) int {
nextStep = prevStep
} else { // delta > 4
// Steps down
nextStep = prevStep + delta - stepsPerTurn
nextStep = prevStep + delta - stepsPerGroup
if nextStep < 0 {
nextStep = 0
}
@ -218,10 +224,10 @@ func (c *cardDisk2) processQ6Q7(in uint8) {
}
if !c.q6 {
if !c.q7 { // Q6L-Q7L: Read
track := d.tracksStep / 4
track := d.tracksStep / stepsPerTrack
c.dataLatch, d.position = d.diskette.read(track, d.position)
} else { // Q6L-Q7H: Write the dataLatch value to disk. Shift data out
track := d.tracksStep / 4
track := d.tracksStep / stepsPerTrack
d.position = d.diskette.write(track, d.position, c.dataLatch)
}
} else {
@ -299,7 +305,7 @@ func (d *cardDisk2Drive) save(w io.Writer) error {
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, d.magnets)
err = binary.Write(w, binary.BigEndian, d.phases)
if err != nil {
return err
}
@ -319,7 +325,7 @@ func (d *cardDisk2Drive) load(r io.Reader) error {
if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &d.magnets)
err = binary.Read(r, binary.BigEndian, &d.phases)
if err != nil {
return err
}