Clock using Instant Interrupts

[Bruce]

If you use Timer2 for your clock it leaves Timer1 free to be used with hardware capture. Then you can use capture to read your IR signal.

Here's an example tested with the SLED-C4. It only needs to test for the TMR2IF flag to keep time, so no interrupts are used. And you have quite a few instruction cycles to do other things between clock updates.

@ DEVICE LVP_OFF,WDT_OFF,MCLR_OFF,XT_OSC

DEFINE OSC 4
DEFINE DEBUG_REG PORTB
DEFINE DEBUG_BIT 0
DEFINE DEBUG_BAUD 19200
DEFINE DEBUG_MODE 0 ' SLED-C4 serial mode = true
    
' 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

PORTB.0=1          ' make sure SLED-C4 data input pin idles high        
TRISB = %00001000  ' RB3 = CCP1 capture input, rest outputs
CMCON = 7          ' disable comparators
INTCON = 0         ' not using interupts. Just monitoring int flag bits

PAUSE 250          ' let SLED-C4 power-up

Time = 0           ' clear TMR2 to PR2 match counter
Hours = 10         ' set clock starting hour here
Minutes = 03       ' set clock starting minutes here

' set SLED-C4 start time
DEBUG "D", Hours DIG 1,Hours DIG 0,Minutes DIG 1,Minutes DIG 0

' TMR2 increments from 0 until it matches the PR2 register value
' and then resets to 0 (on the next increment cycle) so place a
' value in PR2 1 cycle short of what you want. Here we want 250 for
' 60mS, so we write 249 to PR2.
PR2 = 249           ' 249 +1 extra cycle for reset = 250*16*15*1uS=60mS
Match = 0           ' clear match flag

' setup & start TMR2
T2CON = %01110110  ' 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 THEN          ' has TMR2 matched PR2? (should happen every 60mS)
      Match = 0           ' yes. clear TMR2 to PR2 match flag bit
      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 minute count
         IF Minutes = 60 THEN  ' have 60 minutes passed?
            Minutes = 0        ' yes. roll-over minutes from 59 to 00
            Hours = Hours + 1  ' update hour every 60 minutes
            IF Hours = 24 THEN Hours = 0 ' roll-over hours from 24 to 00
         ENDIF                 
         ' print new time only once every minute
         DEBUG "D", Hours DIG 1,Hours DIG 0,Minutes DIG 1,Minutes DIG 0 
      ENDIF    
   ENDIF
   
   GOTO Main
   
   END

It's pretty decent at keeping time. Ran for 3 hours, and it was spot-on with my PC clock to the second.

[PICpocket]

Thanks for the help both Darrel and Bruce!

I kicked myself for not seeing that I wasn't resetting the Counts in my first posting However, things are working well now, and I can read my IR signal as I want by putting the clock routine as my interrupt and the IR PULSIN command as my main (as Darrel suggested). At this point is it just some coding to recognize alarms and different programmable options that I will throw in.

I don't think I will have a problem with having enough time for tasks between interrupts since I am only doing the initial PULSIN command in my Main. If there was some kind of restriction in the interrupt routine I might have a problem them, but most of the heavy coding will be outside the main and the Interrupt routine. Though the code Bruce posted is very concise. I will try things out with both of them and see how things go.

Ill post here if I have any more questions.