Silicon Laboratories Stepper Machine User Manual download pdf (Page 30)

AN155

30 Rev. 1.1

PatternIndex &= 0x07; // fix modulus 8 counter

Position--; // increment Position

}

// output step pattern, set bit 7 because it is an input

P0 = StepPattern[PatternIndex] | 0x80;

// determine motor state based on counter values

if (SlewCount == 0)

if (TableIndex == 0)

motorState = DONE;

else

motorState = DECELERATE;

else

if (TableIndex < MaxTableIndex)

motorState = ACCELERATE;

else

motorState = SLEWING;

if (motorState == DONE)

{

ET0 = 0; // disable T0 interrupts

TR0 = 0; // stop T0

LED = OFF; // turn off LED

doneFlag = 1; // display done message

}

else

{

// get value from table, multiply by T zero

TableValue = StepTable[TableIndex];

offset = MUL8x8(Tzero, TableValue);

TR0 = 0; // stop Timer0

time.b.lo = TL0; // read lo byte first

time.b.hi = TH0; // read hi byte second

time.w = time.w - offset; // calculate new time

TL0 = time.b.lo; // write lo byte first

TH0 = time.b.hi; // write hi byte second

TR0 = 1; // start Timer0

if (motorState == DECELERATE) // if decelerating

TableIndex--; // decrement table index

else if(motorState == ACCELERATE)// if accelerating

TableIndex++; // increment table index

else if (motorState == SLEWING) // if slewing

SlewCount--; // decrement slewCount

ET0 = 1; // enable Timer0 interrupts

}

//-----------------------------------------------------------------------------

unsigned int MUL8x8(unsigned char a, unsigned char b)

{

unsigned int ab;

ab = (unsigned int) a * b; // cast a to int to trick compiler

return ab; // return int

}

//-----------------------------------------------------------------------------

void puts(char *string) // puts a string into send buffer

{

while(*string) // while not null character

{

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Silicon Laboratories Stepper Machine User Manual Page 30

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