pic freezing. stop working

[lmercor]

hello I have a little problem with a hardware I developed.
I'm using a pic18f4550 is kind a large amount of code, and when the hardware start works great, but after a couple of hours it suddenly stop working. I really don't know why, because it start perfect and works perfect for 3 or 4 hours. I've heard that I can use the watchdog to solve this kind of problems, but i don't really have idea how to set up the watchdog, because I've never used it. as I said before I'm using the pic18f4550 and the compiler version is 4.013 and I also have the 3.249.

please can anyone give me a hand with this.

Thanks

[PCM programmer]

There are many possible reasons. It could be:
1. Problems in the crystal oscillator circuit
2. Forgetting to add NOLVP to the #fuses
3. Leaving off the ERRORS directive in the #use rs232() statement
4. Lack of 100 nF capacitors to Ground on each of the PIC's Vdd pins.
5. Over-writing the end of an array.
6. Using "too high" of an #opt level.
7. Also, vs. 4.013 is considered to be an "early" version of the compiler.
It might be too buggy to use for your application. Try using vs. 3.249.

There are really tons of other possible reasons.
This post has links to some more of them:
http://www.ccsinfo.com/forum/viewtopic.php?t=30368&start=1

[lmercor]

thanks for your reply.

[SherpaDoug]

The watchdog is a poor solution, but an easy one. It is better to find the root of the real problem. In addition to what others have said I would also look hard at ESD (static electricity). Does it fail when you touch something or slide something?
_________________
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[lmercor]

[PCM programmer]

Run a very simple program that just flashes an LED. Run it all night.
See if it locks up. If so, there is likely a hardware problem.

[PCM programmer]

I think I should revise that. It could also be some software interaction
with the RFID device (or some other external device). It could be polling
some status bit from the RFID device, and perhaps the code gets stuck
in that polling loop forever.

Here's a thread where that apparently was the problem.
http://www.ccsinfo.com/forum/viewtopic.php?t=31335

[lmercor]

thank you everyone. I will check everything you have mentioned.

Thank you very much again.

[L.Belanger]

maybe did you put a pull up res on the MCLR pin ?
sounds stupid but actually i forget sometimes ;)

+ Does the Xtal have caps on it ? 22pf on each pin to ground to stabilize it... is recommended

[lmercor]

I'm using the MCLR pin as input, and of course it has the Xtal capacitors

[ELCouz]

hmmm seriously if your code is ok ,,, then check for power spikes in your voltage ... IMHO i would try on another PIC18F4550

btw, a watchdog will reset you pic if freezed,,, you don't want to have your pic resetted every 3-4 hours ;)

[lmercor]

Well, I did change the pic for another 4550, but yesterday I tried using a 4455 which is almost the same as the 4550 and I left it all night and until now it still working fine.

Thank you for your help.