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microEngineering Labs, Inc. | 1-719-520-5323 | Example Program - CLOCKX3.pbp

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 time.
' Name        : CLOCKX3.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    : 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 time.
'

Define LCD_DREG  PORTA   ' Define LCD connections
Define LCD_DBIT  0
Define LCD_RSREG PORTA
Define LCD_RSBIT 4
Define LCD_EREG  PORTB
Define LCD_EBIT  3

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

   CMCON = 7       ' PORTA digital
   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
   OPTION_REG = $55 ' Set TMR0 configuration and enable PORTB pullups
   INTCON = $a0     ' Enable TMR0 interrupts
   
   On Interrupt Goto tickint

   PORTB = 0         ' PORTB lines low to read buttons
   TRISB = %11001111 ' Enable buttons

' Main program loop - in this case, it only updates the LCD with the time
mainloop:
   ' Check any button pressed to set time
   If PORTB.7 = 0 Then decmin
   If PORTA.5 = 0 Then incmin

' 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
      hour = hour + 1
      If hour >= 24 Then
         hour = 0
      Endif
   Endif
   Goto debounce

' Decrement minutes
decmin:
   minute = minute - 1
   If minute >= 60 Then
      minute = 59
      hour = hour - 1
      If hour >= 24 Then
         hour = 23
      Endif
   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

           

Download the program file.