' Name        : CLOCKX4.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM
' Target PIC  : 8-pin PIC12F675 or similar type
' Hardware    : Lab-X4 board
' Oscillator  : 4MHz internal
' Keywords    : ON INTERRUPT, SEROUT2, TIMER0
' Description : PICBASIC PRO program for LCD clock using On Interrupt.
' Uses TMR0 and prescaler. Watchdog Timer should be set to off at program
' time and Nap and Sleep should not be used. Button may be used to set time
'

@ device intrc_osc_noclkout, wdt_off, mclr_off

Define OSCCAL_1K 1      ' PIC12F675, Calibrate internal oscillator

LCD     Var     GPIO.1  ' LCD TX pin
PB      Var     GPIO.3  ' Alias GPIO.3 to push button

T2400   Con     396     ' 2400 baud, true

hour    Var     Byte    ' Define hour variable
dhour   Var     Byte    ' Define display hour variable
minute  Var     Byte    ' Define minute variable
second  Var     Byte    ' Define second variable
ticks   Var     Byte    ' Define pieces of seconds variable
update  Var     Byte    ' Define variable to indicate update of LCD
i       Var     Byte    ' Debounce mainloop variable

   ANSEL = 0       ' Set all digital
   CMCON = 7       ' Analog comparators off

   Pause 500       ' Wait for LCD to startup

   hour = 0        ' Set initial time to 00:00:00
   minute = 0
   second = 0
   ticks = 0

   update = 1      ' Force first display

' Set TMR0 to interrupt every 16.384 milliseconds
   OPTION_REG = $d5    ' Set TMR0 configuration
   INTCON = $a0        ' Enable TMR0 interrupts
   
   On Interrupt Goto tickint

' Main program mainloop
mainloop:
   ' Check button pressed to set time
   If PB = 0 Then
      minute = minute + 1     ' Increment minutes
      If minute >= 60 Then
         minute = 0
         hour = hour + 1
         If hour >= 24 Then
            hour = 0
         Endif
      Endif
      For i = 1 To 100        ' Debounce and delay for 100ms
        Pause 1               ' 1ms at a time so no interrupts are lost
      Next i

      update = 1              ' Set to update screen
   Endif

   ' Check for time to update screen
   If update = 1 Then
      ' Display time as hh:mm:ss
      dhour = hour             ' Change hour 0 to 12
      
      If (hour // 12) = 0 Then
         dhour = dhour + 12
      Endif

      INTCON = $80              ' No interrupts during Serout2

      ' Check for AM or PM
      If hour < 12 Then
         Serout2 LCD, T2400, [$fe, 1, dec2 dhour, ":", dec2 minute, ":", dec2 second, " AM"]
      Else
         Serout2 LCD, T2400, [$fe, 1, dec2 (dhour - 12), ":", dec2 minute, ":", dec2 second, " PM"]
      Endif

      update = 0   ' Screen updated
      INTCON = $a0 ' Enable TMR0 interrupts
   Endif

   Goto mainloop   ' Do it all forever

   ' Interrupt routine to handle each timer tick
   Disable         ' Disable interrupts during interrupt handler

tickint:
   ticks = ticks + 1         ' Count pieces of seconds
   If ticks < 61 Then tiexit ' 61 ticks per second (16.384ms per tick)

  ' One second elasped - update time
   ticks = 0
   second = second + 1
   If second >= 60 Then
      second = 0
      minute = minute + 1
      If minute >= 60 Then
         minute = 0
         hour = hour + 1
         If hour >= 24 Then
            hour = 0
         Endif
       Endif
   Endif

   update = 1      ' Set to update LCD

tiexit:
   INTCON.2 = 0    ' Reset timer interrupt flag
   Resume

   End