' Name        : SERVOX3.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM or MPASM
' Target PIC  : PIC16F627A or similar 18-pin type compatible with LAB-X3 board
' Hardware    : LAB-X3 Experimenter Board
' Oscillator  : 4MHz external crystal
' Keywords    : IF THEN, LCDOUT
' Description : PICBASIC PRO program to move an RC servo using buttons.
' Button 1 moves servo left, 2 moves servo right. Press both buttons to
' center servo.
'

' Define LCD registers and bits
Define LCD_DREG  PORTA
Define LCD_DBIT  0
Define LCD_RSREG PORTA
Define LCD_RSBIT 4
Define LCD_EREG  PORTB
Define LCD_EBIT  3

pos     Var Word     ' Servo position
servo1  Var PORTB.6  ' Alias servo pin

   CMCON = 7            ' PORTA to digital
   Pause 100            ' Wait for LCD to startup
   OPTION_REG = $7f     ' Enable PORTB pullups
   Low servo1           ' Servo output low

   Gosub center         ' Center servo

' Main program loop
mainloop:
   ' Check any button pressed to move servo
   If PORTB.7 = 0 Then
      If PORTA.5 = 0 Then
         Gosub center
      Else
         Gosub left
      Endif
   Endif
   If PORTA.5 = 0 Then
      Gosub right
   Endif

   servo1 = 1           ' Start servo pulse
   Pauseus 1000 + pos
   servo1 = 0           ' End servo pulse
   Pause 16             ' Servo update rate about 60Hz
   Goto mainloop        ' Do it all forever

' Move servo left
left:
   if pos < 1000 Then
      pos = pos + 1
      Lcdout $fe, 1, "Position = ", #pos
   Endif
   Return

' Move servo right
right:
   If pos != 0 Then
      pos = pos - 1
      Lcdout $fe, 1, "Position = ", #pos
   Endif
   Return

' Center servo
center:
   pos = 500
   Lcdout $fe, 1, "Position = ", #pos
   Return

   End