Time delay by incrementing a variable using incoming pulse

[jmgelba]

Im trying to capture the 60Hz mains signal count the pulses up to 600, then go and do the subroutine "addtenthhour", then update the display. Then return to counting the incoming pulses, hit 600 and do it all over again.
However, it aint working.
My input is RA5, I have a 0-4.5v square wave coming into the pin. Its robust and is clean on the scope.
What the heck am I missing here??

MainLoop:
A0 = 0
IF PORTA.5 = 1 THEN A0 = A0 + 1
A1 = A0
IF A1 = 600 THEN AddHourTenth
Gosub DisplayRefresh
Goto MainLoop


AddHourTenth:
HoursL = HoursL + 1
IF HoursL = 0 THEN HoursH = HoursH + 1
IF (HoursH = $F) and (HoursL = $4240) then ; Roll over at 1,000,000
HoursH = 0 ; 99999.9 + .1
HoursL = 0
endif
GOSUB WriteHours_EE
A1 = 0
Return

[Ron Marcus]

MainLoop:
A0 = 0
IF PORTA.5 = 1 THEN A0 = A0 + 1
A1 = A0
IF A1 = 600 THEN AddHourTenth
Gosub DisplayRefresh
Goto MainLoop

It looks like every time you hit MainLoop, you reset A0 to zero. Subsequently, you put the A0 value into A1. This gets repeated every loop. The most A1 can increment to is 1. Also you have a goto statement to a sub loop, with a return at the end. Either have a gosub with a return or a goto with a follow up goto. Otherwise there will be stack problems.

Ron

[jmgelba]

Ok, so if I make A0 = 0 before mainloop to initilize the count at zero. I change the line:
IF A1 = 600 THEN AddHourTenth
into
IF A1 = 600 THEN Gosub AddHourTenth

I end up with this...

A0 = 0
MainLoop:
IF PORTA.5 = 1 THEN A0 = A0 + 1
A1 = A0
IF A1 > 600 THEN A1 = 0
IF A1 = 600 THEN Gosub AddHourTenth 'adds increment of value to be displayed
Gosub DisplayRefresh 'places new value on the 7 segment displays
Goto MainLoop

Does this take care of the issues?


Or should I be doing it like this?

IF A1 = 600 THEN
Gosub AddHourTenth
ELSE
Goto Mainloop
ENDIF

[Charles Linquis]

Curious: If you are trying to implement a "power on hours" counter, I can think of a better way - one that doesn't use so much processor time.

[mister_e]

i had the same feeling too. Using Timer interrupt by example. Look in your datasheet. There's at least one pin that can be assign as clock source for an internal timer. In many case it's RA.4

Wich PIC are you using?

[Charles Linquis]

And if you aren't comfortable with interrupts, you can sit in a loop and watch for a timer overflow, reload the timer, run your main program and go back to the loop. As long as your main program takes less time to execute than the timer overflow period (extremely likely), everything works perfectly.

I do this all the time for run-time counters. If you are using 18F devices, you can easily get a 2 second period, even if you are running at 20Mhz. I count the jumps to MAIN. After 30 jumps, I increment the minutes counter.