Working clock example using 32K watch crystal

Looked all over trying to find an example with a second crystal connected to the TIMER1 overflow. This example uses the earlier 18F452 version of the Olimex PIC-WEB board. Ran the clock for a day without gaining or loosing a second! Lots of places where I was not sure what to do. Comments are welcome.
Regards
Tim C

Code:

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' Name        : TMR1CLK.pbp
' Target PIC  : PIC18F452 or similar 18F types
' Hardware    : PIC-WEB ver A board with added LCD
' Oscillator  : 10MHz crystal. You May have to modify default 18F452 fuses for > 4Mhz
' Resolution  : Expect to get +- 5sec/day or better
' Description : PicBasic Pro program using external 32K watch xtal and Timer1
' interrupt for a real-time clock.
' Origional ver from: http://melabs.com/resources/samples/18f/tmr1clk18.htm 
'
DEFINE      OSC 10          ' We're using a 10MHz oscillator
DEFINE      LOADER_USED 1  ' Boot-Loader is being used
Define                INTHAND myint        ' Define interrupt handler
Symbol                LED_0 = PORTD.5
symbol                BUTTON_0 = PORTB.0

wsave                VAR BYTE bankA system  ' Saves W
ssave                VAR BYTE bankA system  ' Saves STATUS

seconds                VAR BYTE bankA  ' variables within myint must be in bank 0.
minutes                VAR Byte      ' Elapsed minutes
hours                var byte

' LCD config
Define  LCD_DREG  PORTD
Define  LCD_DBIT  0
Define  LCD_RSREG PORTE
Define  LCD_RSBIT 0
Define  LCD_EREG  PORTE
Define  LCD_EBIT  1

  ADCON1 = 7          ' Set PORTA and PORTE for digital operation
  Low PORTE.2        ' Enable the LCD

  Pause 150          ' Pause to allow LCD to initialize
  LCDOut $fe,1        ' Clear LCD

        hours = 2
        minutes = 23      ' Pre Set time here then add seconds to clock using button
        seconds = 0

        T1CON.7=0        ' 8 Bit r/w (16 bit seems to cause problems)
        T1CON.5=0        ' Part 1 of 1:1 prescale
        T1CON.4=0        ' Part 2 pf 1:1 prescale
        T1CON.3=1        ' turn on the low freq clock osc
        T1CON.2=1        ' Do not Sync low Freq clock with main clock
        T1CON.1=1        ' use 32Khz xtal as the Timer1 source
        T1CON.0=1        ' enable Timer1
               
        PIE1 = $01        ' Enable TMR1 overflow interrupt
        INTCON  = $C0      ' Finally Enable global interrupt and peripheral interrupts

  GoTo mainloop          ' jump over the interrupt handler and sub

  ' Assembly language interrupt handler
Asm
myint
  ; Save the state of critical registers
  movwf  wsave      ; Save W
  swapf  STATUS, W  ; Swap STATUS to W (swap avoids changing STATUS)
  clrf    STATUS    ; Clear STATUS
  movwf  ssave      ; Save swapped STATUS

  ; Set the high register of Timer1 to cause an interrupt every
  ; 32768 counts (2^15).

  movlw  080h      ; Prepare to set TMR1 high register
  movwf  TMR1H      ; Set TMR1H to 80h
  incf    _seconds,F ; INCREMENT seconds COUNT
  bcf    PIR1, 0    ; Clear interrupt flag

  swapf  ssave, W  ; Retrieve the swapped STATUS value (swap to avoid changing STATUS)
  movwf  STATUS    ; Restore it to STATUS
  swapf  wsave, F  ; Swap the stored W value
  swapf  wsave, W  ; Restore it to W (swap to avoid changing STATUS)
  retfie            ; Return from interrupt
EndAsm

' Subroutine to update the time variables
get_time:

        if seconds > 59 then
                seconds = seconds - 60        ' better then making seconds=0
                minutes = minutes + 1
                if minutes > 59 then
                        minutes = 0
                        hours = hours + 1
                        if hours > 12 then        ' simple 12 hour clock format
                                hours = 1
                        endif
                endif
        endif     

Return

mainloop:

        GoSub get_time      ' Update minutes and seconds
        TOGGLE LED_0

        LCDOut $fe,2,"Time: ",DEC hours, ":", DEC2 minutes, ":", DEC2 seconds, "  "

        Pause 300          ' Pause to see LED blink. Also help with debounce
        if button_0 = 0 then
                LCDOut $fe,$C0,"+1s "
                seconds = seconds + 1
                else
                LCDOut $fe,$C0,"    "
        endif
        GoTo mainloop      ' Repeat main loop

  End

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Quote:

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' Description : PicBasic Pro program using external 32K watch xtal and Timer1

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But 50% of the program is in assembler :)

Quote:

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Originally Posted by malc-c

But 50% of the program is in assembler :)

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Then show him how it's done. (in straight PBP) :D
This task is worth 2 free 4x20 Parallel LCD's ... shipping outide of US/Canada extra.

In case of multiple responses ... style will prevail.
As judged by Darrel Taylor
Ends 11/10/2010 Midnight Mountain Time

INCLUDE "DT_INTS-18.pbp" ; Base Interrupt System
INCLUDE "ReEnterPBP-18.pbp" ; Include if using PBP interrupts"

The earlier versions I wrote had NO asm but lost almost a minute an hour. To make up for that one could re-tune using TMR1H and TMR1L with a larger value. Problem is every change made to the program would mean spending a few days retuning and it would never be as precise.

So yea I would love to be able to do this without asm in PBP AND be as accurate!

Down the road I intend to join this interrupt sample with a SNTP internet program so I can have a near perfect millisecond low power $60 clock.

Regards
Tim C

Code:

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  ' Int handler doesn't mess with any PBP system variables - or lower 15-bits
  ' of TMR1 accumulated time. Uses only 4 instructions to set TMR1H high bit,
  ' increment seconds, clear the interrupt flag bit, save & restore WREG, STATUS,
  ' BSR and return from int handler.
 
@myint                  ; create myint label
  TMR1H.7=1            ' Set TMR1 high bit for 1 second overflows
  seconds = seconds+1  ' Increment seconds
  PIR1.0=0            ' Clear TMR1 int flag
  @ retfie  FAST      ; Return with 'auto restore' of WREG, STATUS and BSR

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Should do it.

Quote:

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Originally Posted by Darrel Taylor

Then show him how it's done. (in straight PBP) :D

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I wish --- (I'll remove my tongue from in my cheek now :) )

Thank you Bruce
Smaller, tighter, yet perfect speed. Started the clock last night with your change and so far the PIC18F452 has not gained or lost one second.
Tim C

Hi,

I didn't see that one :
http://www.pbpgroup.com/modules/wfse...hp?articleid=8

did I miss something ???

Alain

Alain,
Darrel's great example uses one crystal mine uses 2. And oh if something is sitting there soldered to the dev board and you don't have code to see if it works!!

Quote:

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Originally Posted by timc

Alain,
Darrel's great example uses one crystal mine uses 2. And oh if something is sitting there soldered to the dev board and you don't have code to see if it works!!

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Hi, Timc

Lol ... I didn't remember I had modified Darrel's code to use a 32 Khz Xtal ...

and thought it was already done in the original release ...

Here it is.

Alain

There's a couple good examples. I like Bruce's.
But it uses in-line assembly language instead of straight PBP.

The Elapsed Timer modification is nice too ... but ...

Nobody wins the LCD's. :(

I was playing with TimC RTC code, and I found 1 problem...
If the interrupt occurs between these lines

Code:

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      GoSub get_time      ' Update minutes and seconds
      TOGGLE LED_0
      LCDOut $fe,2,"Time: ",DEC hours, ":", DEC2 minutes, ":", DEC2 seconds, "  "

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There is a chance to show 60 seconds.
It happened to me, so I then wondered what was going on...
Solution:

Code:

---

seconds        VAR BYTE bankA  ' variables within myint must be in bank 0.
minutes        VAR Byte bankA      ' Elapsed minutes
hours          var byte bankA
:
:
:
@myint                  ; create myint label
  TMR1H.7=1
    seconds = seconds+1  ' Increment second
    if seconds > 59 then
        seconds = seconds - 60    ' better then making seconds=0
        minutes = minutes + 1
        if minutes > 59 then
            minutes = 0
            hours = hours + 1
            if hours > 12 then hours = 1    ' simple 12 hour clock format
        endif
    endif
 PIR1.0=0            ' Clear TMR1 int flag
  @ retfie  FAST

---

And remove get_time procedure

I'm trying to add the calendar.
Does anyone have an idea how to make a calculation of leap year.
I tried this
If day>30+month.0 or (Month=2 and day>28 and year//4<>0) or (Month=2 and day>29 and year//4=0)then
month=month+1
but the code is 300b larger then this
If day>30+month.0 or (Month=2 and day>28)then
month=month+1
Is there a more efficient way?

How about using 3 If-Then's insead of one with 3 OR's?

Ioannis

I spent all night trying to find the best way ... I think this is

Code:

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              If month=2 then
                If year//4<>0 then
                    DMonth=29
                else
                    DMonth=28
                endif
              else
              Dmonth=30+month.0
              endif 
              If day>Dmonth then
@                CLRF _Day
@                INCF _Month,F
                If month>12 then

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And everywhere there is any = 0, I replaced the @ clrf, +1 replaced with @ incf.
The end result was the RTC which consumes about 2uA and code size about 500B. :o

I think you have to change the <>0 to =0 when you test for the modulo 4.

A better solution to cover more years (you code will not cover year 2100) is to use mod 400, mod 100 and mod 4 to test for leap year (mod 100 is NOT leap year, while 400 and 4 ARE leap years).

Of course we may not live in year 2100, but just in case... :)

Now about the @ commands, just be sure you are on page 0. Else you have to check the page bits. Or put this subroutine on top of your code.

Ioannis

Thanks for that... It was just typo... 0-99 year is fine for this aplication.
On the top of ISR I have BSR=0, and isr routine is on top of my programm.

If I may suggest, make the minutes and hours update in your main loop and not in Interrupt. A temp variable wll be needed for this.

Ioannis

If pic loses power, it goes to sleep. And everything is shut off, only tmr1 is on. So i need that in ISR. Is there better way?