' Name        : CLOCKXU.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : MPASM
' Target PIC  : PIC18F4550 or similar type
' Hardware    : LAB-XUSB Experimenter Board
' Oscillator  : 20MHz external
' Keywords    : ON INTERRUPT, LCDOUT, TIMER0
' Description : PICBASIC PRO program for an 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. Buttons may be used to set hours
' and minutes.
'

' Define LOADER_USED to allow use of the boot loader.
' This will not affect normal program operation.
Define LOADER_USED 1

' RESET_ORG can be set to move the BASIC program out of the way
' of any boot loader running from location 0, such as the
' Microchip USB boot loader
'Define RESET_ORG 800h

Define OSC 48      ' Core is running at 48MHz

' Define LCD pins
Define LCD_DREG  PORTD
Define LCD_DBIT  4
Define LCD_RSREG PORTE
Define LCD_RSBIT 0
Define LCD_EREG  PORTE
Define LCD_EBIT  1

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 loop variable

   INTCON2.7 = 0  ' Enable PORTB pullups
   ADCON1 = 15    ' PORTA and E digital
   Low PORTE.2    ' LCD R/W low = write
   Pause 100      ' 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
   T0CON = $c7     ' Set TMR0 configuration
   INTCON = $a0    ' Enable TMR0 interrupts
   
   On Interrupt Goto tickint

' Main program loop - in this case, it only updates the LCD with the time
mainloop:
   PORTB = 0        ' PORTB lines low to read buttons
   TRISB = $f0      ' Enable all buttons

   ' Check any button pressed to set time
   If PORTB.7 = 0 Then decmin
   If PORTB.6 = 0 Then incmin ' Last 2 buttons set minute
   If PORTB.5 = 0 Then dechr
   If PORTB.4 = 0 Then inchr  ' First 2 buttons set hour

' Check for time to update screen
chkup:
   If update = 1 Then
      Lcdout $fe, 1   ' Clear screen

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

      ' Check for AM or PM
      If hour < 12 Then
         Lcdout dec2 dhour, ":", dec2 minute, ":", dec2 second, " AM"
      Else
         Lcdout dec2 (dhour - 12), ":", dec2 minute, ":", dec2 second, " PM"
      Endif
      update = 0   ' Screen updated
   Endif
   Goto mainloop   ' Do it all forever

' Increment minutes
incmin:
   minute = minute + 1
   If minute >= 60 Then
      minute = 0
    Endif
   Goto debounce

' Increment hours
inchr:
   hour = hour + 1
   If hour >= 24 Then
      hour = 0
   Endif
   Goto debounce

' Decrement minutes
decmin:
   minute = minute - 1
   If minute >= 60 Then
      minute = 59
   Endif
   Goto debounce

' Decrement hours
dechr:
   hour = hour - 1
   If hour >= 24 Then
      hour = 23
   Endif

' Debounce and delay for 250ms
debounce:
   For i = 1 to 25
     Pause 10           ' 10ms at a time so no interrupts are lost
   Next i
   update = 1           ' Set to update screen
   Goto chkup

' Interrupt routine to handle each timer tick
   Disable              ' Disable interrupts during interrupt handler
tickint:
   ticks = ticks + 1    ' Count pieces of seconds
   If ticks < 200 Then tiexit ' 200 ticks per second

   ' 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