AVR-Chat

Are you using any optimization?

I vaguely recall a problem similar to this.  It may have something to do with "volatile".

...Just a thought.

--- In AVR-Chat@yahoogroups.com, Cat C <catalin_cluj@...> wrote:
>
> 
> I just discovered that using (or not) the watchdog only changes the values at which the problem happens, and it was undetected before because I wasn't using the Timer1 values where it happens without the watchdog.
> 
> I'd still like to know why the watchdog changes anything in a mainly interrupt-driven timing setup, but ...
> 
> Thanks,
> 
> Cat
> 
> From: catalin_cluj@...
> To: avr-chat@yahoogroups.com
> Subject: Using WatchDog messes up timings in my code (ATMega644P 20AU)
> Date: Thu, 11 Mar 2010 11:03:22 -0700
> 
> 
> 
> 
> 
> 
> 
> 
> Hi,
> Got this very strange problem(s).
> 1. For some reason, at power-up (4.5V from linear on-board regulator from PC 5V PSU) the microcontroller starts up temporarily but then stops (or goes to microcontroller heaven).  I know this because I'm sending some text on the serial port near the start of the program and I only get some of it.
> If I press the reset button all is fine, so maybe strange things happen because power might go up too slow.
> I decided to use the watchdog so if it doesn't get to the main loop (where it gets kicked) it will reset the board.
> 
> This seems to work, but:
> 2. Some timings that work fine when I don't use the watchdog now get messed up in the strangest way:
> Depending on a value I set in Timer 1, I get a big change in Timer 0 (a period supposed to be about 440us is now about 3ms).
> 
> There are still things to check, but... does anybody have an idea that might save me some time?
> 
> Any help appreciated, thank you,
> 
> Cat
> 
> PS - when I enable the watchdog I'm NOT setting the fuse, just in SW:
> 
> #include <avr/wdt.h>
> 
> main()
> {
> ...
>      wdt_enable(WDTO_1S);
> ...
>      while (1)
>      {
>      wdt_reset ();
>      .....
> .....}
> 
> The timing routines are quite complex, involving setting Timer0 inside interrupt handler of Timer1, etc.
>  		 	   		  
> 
> [Non-text portions of this message have been removed]
>