AVR-Chat

Dammit. I got bit again.

Now those who know me here, know that this is a hot button issue for
me, and I'm posting this to illustrate just how sneaky this problem
is.


I'm currently using an M644 with 20 Mhz external crystal, for a sensor
processing app.
I'd scanned the data sheet, and did not see any mention of the dreaded
"CKOPT" fuse, and so ASSUMED that it was not an issue.

WRONG..

The low fuses for my crystal should have been set to 0xD7, but I'd set
them to 0xDF, which is one bit off, and activates the low power
"vittoz" mode oscillator.

I've been having bad and intermittent problems with the Jtag ice MkII,
and I'd been having glitches in my serial output, which I was thinking
were probably some issue with my code.

Now that the fuses are properly set, I'll do some testing on Monday
and verify with a single build on both modes, wether those glitches
were caused by clocking problems.

Only time will tell on the Ice problems, they come and go seemingly at random.


I do wonder, is there anyone out there who actually is intentionally
using the low power oscillator, with a properly designed and reliable
crystal circuit?

I'll repeat my advice on this, NEVER NEVER NEVER USE THE LOW POWER
CRYSTAL OSCILLATOR.
If you think you need it, and you're SURE you understand all the
implications, and you're SURE that you've made all the measurements,
then feel free to ignore my advice.
For hobbyists, and even most commercial users, this mode is just
absolutely begging for trouble.



-- 
There is no computer problem which cannot be solved by proper
application of a sufficiently large hammer.