' -------------------------------------------------------------------------
' Program Description
' -------------------------------------------------------------------------
'
' Uses PWM through an RC network to create an analog voltage.

' -------------------------------------------------------------------------
' Device Settings
' -------------------------------------------------------------------------

DEVICE          SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ            4_000_000
ID              "PWM"

' -------------------------------------------------------------------------
' IO Pins
' -------------------------------------------------------------------------

DAC             VAR     RB.0                    ' output to RC network

' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------

angle           VAR     Byte
duty            VAR     Byte

tmpB1           VAR     Byte
tmpB2           VAR     Byte

' =========================================================================
  PROGRAM Start
' =========================================================================

' -------------------------------------------------------------------------
' Subroutine Declarations
' -------------------------------------------------------------------------

SIN             SUB     1                       ' returns sine of angle
COS             SUB     1                       ' returns cosine of angle

' -------------------------------------------------------------------------
' Program Code
' -------------------------------------------------------------------------

Start:
  DO
    FOR angle = 0 TO 255                        ' sweep through angles
      duty = SIN angle                          ' get sine of angel
      duty = duty + 127                         ' bias to 2.5 v
      PWM DAC, duty, 1                          ' charge RC network
    NEXT
  LOOP

' -------------------------------------------------------------------------
' Subroutine Code
' -------------------------------------------------------------------------

' Use: value = SIN angle
' -- "value" returned as signed byte (-127 to 127)
' -- angle is expressed in Brads (0 - 255)

SIN:
  tmpB1 = __PARAM1                              ' get angle
  tmpB2 = tmpB1                                 ' make copy
  IF tmpB2.6 = 1 THEN                           ' in 2nd or 4th quadrant?
    tmpB1 = 0 - tmpB1                           '   yes, move to 1st/3rd
  ENDIF
  tmpB1.7 = 0                                   ' reduce to 1st quadrant
  READ SineTable + tmpB1, tmpB1                 ' read sine
  IF tmpB2.7 = 1 THEN                           ' was angle in 3rd/4th?
    tmpB1 = 0 - tmpB1                           '   yes, adjust
  ENDIF
  RETURN tmpB1

' -------------------------------------------------------------------------

' Use: value = COS angle
' -- "value" returned as signed byte (-127 to 127)
' -- angle is expressed in Brads (0 - 255)

COS:
  tmpB1 = __PARAM1 + $40                        ' get angle (adjust phase)
  tmpB1 = SIN tmpB1                             ' call sine table
  RETURN tmpB1


' =========================================================================
' User Data
' =========================================================================

SineTable:
  DATA  000, 003, 006, 009, 012, 016, 019, 022
  DATA  025, 028, 031, 034, 037, 040, 043, 046
  DATA  049, 051, 054, 057, 060, 063, 065, 068
  DATA  071, 073, 076, 078, 081, 083, 085, 088
  DATA  090, 092, 094, 096, 098, 100, 102, 104
  DATA  106, 107, 109, 111, 112, 113, 115, 116
  DATA  117, 118, 120, 121, 122, 122, 123, 124
  DATA  125, 125, 126, 126, 126, 127, 127, 127
  DATA  127