Time delay by incrementing a variable using incoming pulse

[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.

[mister_e]

you should find some hints in the following
http://www.picbasic.co.uk/forum/show...44&postcount=2

look the 2 lasts examples

HTH

[jmgelba]

Thanks for the ideas guys. I'm using a 16F818. It is a run time hourmeter application. I wanted to use the 60 Hz cycle to maintain accuracy over the lifetime of the product. I figured if I counted the pulse and only executed the rest of the program when the correct count had been achieved, this would give me the best accuracy.
The processor is doing a fair amount of work. Its multiplexing through 6, seven segment displays. Its running at 8Mhz using the internal oscillator as I need all the pins.
I currently have RA4 used as an output, and RA5 is the pulse in. The reason is that RA5 is input only and therefore cant be used to drive a segment. I have a spare pin, RA7, which I was intending to use to detect mains power fail, so that I can write to EE before the power fails, as currently, it only writes as it increments a digit.
I will check the datasheet, and if I can set RA5 as an interupt pin I will try it.
Otherwise I will have to shift my power fail detect to RA5 and have RA7 as an output. This will free up RA4.