the code of the digital clock is shown below:
' LCD clock program 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 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
OPTION_REG = $55 ' Set TMR0 configuration and enable PORTB pullups
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
this code was found at melabs.com but since i just started to learn PIC and some of the routine still trouble me.so i hope i can get a flow chart for this clock for best understanding.
thank u