Clock
The following code only work with a 4 Mhz crystal, how can i get it to work with a 20Mhz crystal?
DEFINE OSC 20 does´t help, the clock ticks to fast whit a 20Mhz crystal
I use PicBasic Pro 2.50a
EDIT: I think i can change the number of "ticks" from 61 to something higher but how do i calculate the right value for the tick?
Code:' 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
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