AVR-Chat

Indeed, I'll have to check that one out.  Hmm, limited frequency, 
increased noise susceptability when unchecked, additional amp, rail to 
rail operation when checked.  D@M! that sure sounds like the pill!  I 
never saw that one, that is some really hefty fine print hidden in 
there.  It explains why my 16MHz parts only ran well at 8MHz.

You learn something new every day - I'm going to have to twiddle that 
one and see if it settles my little robots down nicely.

Thanks, you've just saved me some more hair pulling.

DLC

Kathy Quinlan wrote:
> dlc wrote:
> 
>>Not uncommon with AVR's in my experience.  I have yet to get a board 
>>designed that didn't have problems with resets on an AVR or MEGAAVR 
>>part.  I've found that if I run the part at its maximum rated frequency, 
>>I get flaky boards, if I derate by 20% or so then the board gets more 
>>reliable, and if I derate by 50% the clock speed everything works fine. 
>>  This seems to indicate that I've got noise on the clock lines - but 
>>after my first experience with these things I've started designing with 
>>guard rings on my oscillator circuits, whole plane grounds, bypass caps 
>>up the nose, low pass filters on my VDD and everything else I've found 
>>in app notes on the Atmel site, still I can get flaky boards.  I never 
>>have these problems with PICs <did I say that?>.
>>
>>I love these chips, they have speed, capability and low cost.  But oh 
>>the problems with Atmel availability and quirkyness.
>>
>>IMO, YMMV,
>>DLC
> 
> 
> If you want to first check your CKOPT fuse (the default is UNCHECKED, 
> CHECK IT!!!!) that will fix a lot of problems.
> 
> OK if you want to send me the pcb and schematic I can check over, as I 
> have NEVER HAD flaky AVR boards since setting the CKOPT fuse :) I have 
> over 300 ATMega128's in the field right now, (the only problem ones are 
> the ones that have not had the fuse ticked (someone else programmed them 
> lol) (but they are coming back as we take them all to the current 
> revision (some hardware mods and firmware upgrades)
> 

-- 
-------------------------------------------------
Dennis Clark          TTT Enterprises
www.techtoystoday.com
-------------------------------------------------