Re: [avr-gcc-list] ADC anomaly

[Joerg Wunsch]

Douglas Dotson <address@hidden> wrote:

> I have a strange anomaly with the ADC on a MEga32.
> The ref voltage is 2.5, input voltage to channel 2
> is 1.25. ADC reading settles at 511 or so. After
> sitting with no activity for several hours, the ADC
> reading drops to 508 or so but the input voltage
> and ref voltages are stable at their proper values.

Just since nobody else mentioned it so far: are you sure you don't
`overdrive' the clock frequency of your ADC?  If the clock is too
high, it's not that it wouldn't work at all, but the accuracy goes
down the stairs.  (Someone reported in a German newsgroup that the ADC
can even be run at several MHz if only 6 bits of accuracy are
desired.)

p. s.: Please learn how to quote.  Don't fully append the previous
messages below your message.  This is considered impolite, since you
make it harder for anyone else to follow you, just for a few seconds
of time you save yourself.
-- 
J"org Wunsch                                           Unix support engineer
address@hidden        http://www.interface-systems.de/~j/