Elapsed Timer Demo

[Darrel Taylor]

Hi shahidali55,

"tweeking the TimerConst" won't help. 1 count either direction will change the timing by more than you are off. @ 4mhz, 1 count will change the time by about 4 seconds per day.

At 2 seconds per day, it works out to around 23 PPM (parts per million), which is within the normal 50 PPM tolerance of the crystal. Not to mention the +/- 100 PPM variance due to temperature.

To get closer than that, you'll need to calibrate the crystal frequency. You may be able to use a small Trimmer Capacitor in place of one of the capacitors on the crystal. The size needed depends on your crystal, but 0-20pf will probably work.

Other than that, you could simply add 1 second every 12 hours. But if you build more units, that could be problamatic since they won't all be the same.

Here's a couple links to some more crystal info:
http://www.circuitcellar.com/library...ujanos91/3.htm
http://ww1.microchip.com/downloads/e...tes/00588b.pdf
http://ww1.microchip.com/downloads/e...tes/00949a.pdf

[shahidali55]

I dont think the problem is with the oscillator.
I noticed that the time loss takes place every time the hours increase...
Could it be some flaw in the code execution?

[Darrel Taylor]

If its losing time on every change of the hour, and the total loss is 2 seconds per day, then each change of the hour would lose 1/12th or 0.083 seconds.

@ 4mhz, that's 83,000 instruction cycles. No, I don't think it's accidently losing that many instructions to increment an hour. And, looking at the ClockCount interrupt routine, if that were the case, it would also happen on every second, minute, and day as well. Which it doesn't.

Why don't you think it's the crystal?

Have you measured the frequency?

DT

[shahidali55]

when i run Josepino's code, on the same board with the same crystal, i do not get any error.
This is why I think it is a fault in the software...

[Darrel Taylor]

Too bad the guy only gives out HEX files.

Otherwise, we could see what special magic he has, to cancel out the tolerance of crystals.

DT

[shahidali55]

Hi Darrel,
Some where Josepino had mentioned on his site that he had used Roman Black's one_sec.asm routine in his clocks (maybe he mentioned this by accident).
I tried making a similar program in PBP but had no success, till now.
Finally i got the progam running. its the exactly same one_sec.asm routine running with instant interrupts, and guess what,... it worked, and really accurately...
Its even more accurate than the Elapsed Timer...
I'll post the code so that it may be useful for someone...
(I'm not as mean and selfish as Josepino...
and thanks a lot for the instant interrupts program...
Chiao...

[Leonardo]

Hello shahidali55,

It can publish or to send to my mail [email protected] the code and complete circuit since is very interesting its project, congratulations for its idea!.

Leonard

Regards

Hi Darrel,
Some where Josepino had mentioned on his site that he had used Roman Black's one_sec.asm routine in his clocks (maybe he mentioned this by accident).
I tried making a similar program in PBP but had no success, till now.
Finally i got the progam running. its the exactly same one_sec.asm routine running with instant interrupts, and guess what,... it worked, and really accurately...
Its even more accurate than the Elapsed Timer...
I'll post the code so that it may be useful for someone...
(I'm not as mean and selfish as Josepino...
and thanks a lot for the instant interrupts program...
Chiao...

[SelfishJosePino]

No, I didn't mention the Roman Black's web page by accident.

I good to know there is people not mean and selfish like JosePino. Anyway, I found quite interesting this forum.

Regards,
Jose Pino
www.josepino.com

Hi Darrel,
Some where Josepino had mentioned on his site that he had used Roman Black's one_sec.asm routine in his clocks (maybe he mentioned this by accident).
I tried making a similar program in PBP but had no success, till now.
Finally i got the progam running. its the exactly same one_sec.asm routine running with instant interrupts, and guess what,... it worked, and really accurately...
Its even more accurate than the Elapsed Timer...
I'll post the code so that it may be useful for someone...
(I'm not as mean and selfish as Josepino...
and thanks a lot for the instant interrupts program...
Chiao...