LAB-X1 Timer2 Clock

This example shows how to create a 24-hour time clock on the LAB-X1 using Timer2/PR2 match - with buttons to increment hours, minutes, reset the time to 12:00, and reset the Timer2 tick counter.

Also shown is how to use the 16F1934 IOCBF interrupt flags to recognize button presses in the background. I.E. you don't need to poll port pins to detect a change, and no interrupts required.

Code:

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' Name        : T246_1934X.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler  : MPASM
' Target PIC  : 40-pin 16F1934 or similar
' Hardware    : LAB-X1 Experimenter Board
' Oscillator  : 4MHz external crystal
' Keywords    : LCDOUT
' Description : PICBASIC PRO program to demonstrate using Timer2 for a
' 24 hour format clock. Time is shown on the LCD as Time = 11:14 with
' hours : minutes. The keypad is used to increment hours, minutes, reset
' the time to 12:00, and reset the Timer2 tick counter.
'
' Note: Open the 16F1934.INC file in your PBP directory, and comment out the default
' __config settings.
ASM
  __config _CONFIG1, _FOSC_XT & _WDTE_SWDTEN & _PWRTE_ON & _MCLRE_ON & _BOREN_ON & _IESO_ON & _FCMEN_ON
  __config _CONFIG2, _PLLEN_OFF & _LVP_OFF & _VCAPEN_OFF & _STVREN_ON & _BORV_25
ENDASM
 
' 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
 
' setup vars for clock
Time    Var Word      ' accumulates TMR2 to PR2 match counts
Minutes Var Byte      ' minutes
Hours  Var Byte      ' hours
Match  Var PIR1.1    ' TMR2 to PR2 match interrupt flag bit
IocFlag Var INTCON.0  ' portb int-on-change flag bit
 
  Gosub Init        ' jump to hardware initialization routine
 
  Lcdout $fe,1,"Time = ", #Hours DIG 1,#Hours DIG 0,":",#Minutes DIG 1,#Minutes DIG 0
    ' setup & start TMR2 after Lcdout
  T2CON = %01110110  ' set 1:16 prescale, 1:15 postscale, TMR2 on
 
Main:
  ' every 60mS the TMR2IF flag is set, and this routine is entered.
  ' Plenty of time to do other stuff.
  If Match = 1 Then          ' has TMR2 matched PR2? (should happen every 60mS)
      Match = 0                ' yes. clear TMR2 to PR2 match flag bit PIR1.1
      Time = Time + 1          ' increment 60mS count   
      If Time = 1000 Then      ' has 60 seconds (1000*60mS) passed?
        Time = 0              ' yes. clear count
        Minutes = Minutes + 1 ' increment Minutes
        If Minutes = 60 Then  ' roll-over from 59 to 0
            Minutes = 0        ' zero Minutes count
            Hours = Hours + 1  ' and increment Hours count
            If Hours = 24 Then ' roll-over from 23 to 0
              Hours = 0      ' zero Hours count
            Endif
        Endif
        ' Update time on LCD every 60 seconds
        Lcdout $fe,$87,#Hours DIG 1,#Hours DIG 0,":",#Minutes DIG 1,#Minutes DIG 0
      Endif 
  Endif
 
      ' test for key press
  If IocFlag Then    ' if keys SW13, 14, 15 or 16 were pressed,
      Gosub GetKeys  ' get the button/buttons pressed
  Endif
  Goto Main
 
' ===========\ Get Keypad Switch Presses /=========== ' 
GetKeys:
  Pause 500              ' crude debounce for key press
 
  ' SW13 increments Hours
  If IOCBF.4 Then      ' IOCBF.4 = 1 when low edge detected on RB4
      While PORTB.4 = 0  ' wait for key release       
      Wend              '
      Hours = Hours + 1 : Time = 0
      If Hours = 24 Then Hours = 0
  Endif
 
  ' SW14 increments Minutes
  If IOCBF.5 Then      ' IOCBF.5 = 1 when low edge detected on RB5
      While PORTB.5 = 0  ' wait for key release
      Wend              '       
      Minutes = Minutes + 1 : Time = 0
      If Minutes = 60 Then Minutes = 0
  Endif
 
  ' SW15 zeros Time "tick" counter
  If IOCBF.6 Then      ' IOCBF.6 = 1 when low edge detected on RB6
      While PORTB.6 = 0  ' wait for key release
      Wend              '     
      Time = 0
  Endif
 
  ' SW16 resets clock to 12:00
  If IOCBF.7 Then      ' IOCBF.7 = 1 when low edge detected on RB7
      While PORTB.7 = 0  ' wait for key release
      Wend              '       
      Hours = 12 : Minutes = 0 : Time = 0
  Endif
  IOCBF = 0            ' reset all int-on-change bits on exit
  IocFlag = 0
  ' Update LCD on each change
  Lcdout $fe,$87,#Hours DIG 1,#Hours DIG 0,":",#Minutes DIG 1,#Minutes DIG 0
  Return
 
Init:
  ANSELA = 0    ' porta all digital
  ANSELB = 0    ' portb all digital
  ANSELD = 0    ' portd all digital
  ANSELE = 0    ' porte all digital
 
  OPTION_REG.7 = 0    ' enable PORTB pullups 
  PORTB = 0          ' RB3 low
  TRISB = %11110111  ' RB3 = 0 for output to keys 13, 14, 15, 16
  WPUB = %11110000    ' weak pull-ups on for ----> RB4, 5,  6,  7
  IOCBP = 0          ' positive edge disabled
  IOCBN = %11110000  ' negative edge int-on-change enabled for keys
 
  TRISD = 0          ' PORTD all outputs
 
  INTCON = 0          ' not using interupts. Just monitoring int flag bits
  Time = 0            ' clear TMR2 to PR2 match counter
  Hours = 10          ' set clock starting hour to 10 here
  Minutes = 16        ' set clock starting minutes to 16 here
 
  ' TMR2 increments from 0 until it matches the value in the PR2 register.
  ' The match automatically resets Timer2 and sets the Timer2 interrupt flag
  ' bit PIR1.1.
 
  PR2 = 249          ' 0 to 249 = 250. 250*16*15*1uS=60mS
  Match = 0          ' clear PIR1.1 match flag bit
  Pause 100          ' Wait for LCD to start
 
  Return              ' Return to caller
 
  End

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