Elapsed Timer Demo

[jmgelba]

Ticks = Ticks + 1
if Ticks = 100 then
Ticks = Ticks-100
Seconds = Seconds - 1
SecondsChanged = 1
if Seconds = 0 then
Minutes = Minutes - 1
MinutesChanged = 1 Seconds = 59
endif

if Minutes = 0 then
Hours = Hours - 1
HoursChanged = 1 Minutes = 59
endif

if Hours = 0 then
Days = Days - 1
DaysChanged = 1 Hours = 23
endif
endif

To my untrained eyes, this would count down the time at every 100 ticks. I guess the issue, if this works, is how to preloaded the timer with the required start time and how to get it to stop at 0.

[jmgelba]

Seem to be having an issue I cant resolve. I've only use the timer software on a 18F2550 and it worked perfectly. I'm now using a 18F1320 and I've ran into an issue when compiling.

ERROR Line 23: Redefinition of VAR. (DT_INTS-18.bas)
ERROR Line 24: Redefinition of VAR. (DT_INTS-18.bas)
ERROR Line 25: Redefinition of VAR. (DT_INTS-18.bas)

Which are these lines in the code:

wsave       var byte  BANKA  SYSTEM   ' location for WREG
ssave       var byte  BANK0  SYSTEM   ' location for STATUS register
bsave       var byte  BANK0  SYSTEM   ' location for BSR register

I am unsure as to what the problem is and where to start.

I'm using PBP 2.60A and MCS 3.0.0.5

[jmgelba]

Fixed the above issue.

[jmgelba]

Getting frustrated! :-) I've tried a bunch of things to get the counter to count down correctly.

There is a problem at rollover. Let's say the timer is set to 1 hour 1 minute zero seconds, it should start there and one second later change to 1:00:59. It doesn't, it stays at 1:01:00 for 1 second and then counts down from 1:01:59. Then when it gets to 1:00:00 it rolls over to 0:00:00 for 1 minute then the next second its at 0:59:59.
Not really sure what to try. What about a "first run through the interrupt" flag that automatically makes minutes = minutes - 1 and starts the seconds at 59?

[HenrikOlsson]

Hi,
Without thinking too much, how about this:

Hours VAR BYTE
Minutes VAR BYTE
Seconds VAR BYTE

Hours = 1
Minutes = 1
Seconds = 0
Ticks = 100

ISR:
  Ticks = Ticks - 1
  If Ticks = 0 THEN              ' Ticks rolled over, one second has passed
    Ticks = 100                    ' Reset ticks (10ms ticks)

    Seconds = Seconds - 1     ' Count down a second.

    If Seconds = 255 THEN      ' Seconds rolled over
      Seconds = 59                 ' Reset seconds
      Minutes = Minutes - 1      ' Count down a minute

        If Minutes = 255 THEN  ' Minutes has rolled over
          Minutes = 59              ' Reset minutes
          Hour = Hour - 1         ' Count down an hour
        ENDIF
    ENDIF
  ENDIF

/Henrik.

[jmgelba]

Henrik, thank you for your reply. It is very logical.

I came up with this before you posted your reply last night:

if seconds => 59 then
minutes = minutes - 1
minuteschanged = 1
endif
if seconds > 59 then
seconds = 59
endif


if Minutes => 59 and seconds => 59 then
hours = hours - 1
HoursChanged = 1
endif
IF Minutes > 59 then
Minutes = 59
endif

if hours = 0 then
Days = Days - 1 
DaysChanged = 1 
Hours = 0 
endif

IF HOURS > 23 then
HOURS = 23
ENDIF
 
endif
ENDIF

It works and has been running all night. Yours is cleaner though! My issue was I was trying to change numbers at 0 not 0 - 1. Once I realized this is took 2 minutes to fix it.

[jmgelba]

This interrupt based timer runs in the background. Does that mean a pause in the main program will stop it or will it continue to run in the background? I am trying to de-bounce a switch.