' Name        : CLOCK452.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : MPASM
' Target PIC  : PIC18F452 or similar 18F types
' Hardware    : Lab-X1 board
' Oscillator  : 4MHz crystal
' Keywords    : INTERRUPTS, LCDOUT, TIMER0
' Description : LCD timer0 clock program using On Interrupt.
' Buttons may be used to set hours and minutes. Uses an 18F452
' on the LAB-X1 Experimenter Board.
'

Define  LCD_DREG  PORTD   ' Define LCD connections
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

   ADCON1 = 7      ' 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
   INTCON2.7 = 0     ' Enable internal pullups on PORTB
   T0CON = %11010101 ' Set TMR0 on, prescaler 1:64           
   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 < 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