Re: [avr-gcc-list] Troubles with ADC on ATMega16

[Larry Barello]

Dunno: it worked for me.  I got 0-1023 input (ratiometric) and one
input did not affect the others and the results were bit stable.  A
50k pot will have a maximum impedance of 12k, right?

Cheers!

----- Original Message -----
From: "Keith Gudger" <address@hidden>
To: "Larry Barello" <address@hidden>
Cc: "AVR GCC List" <address@hidden>
Sent: Thursday, May 08, 2003 3:56 PM
Subject: Re: [avr-gcc-list] Troubles with ADC on ATMega16


> You call "a 50k pot" low input impedance?  That was about the value
I
> needed 30 us to be able to read.  Remember that the delay needed is
> *between* switching the mux and starting the A/D conversion.
>
> Keith
>
> On Thu, 8 May 2003, Larry Barello wrote:
>
> > I don't wait at all, but I do make sure I have fairly low input
> > impedance.  Either a 50k pot (for variable user input) or put a
.1uf
> > capacitor to filter the input signal.  I am never chasing high
speed
> > signals so I just jammed a large capacitor to clean things up.  If
I
> > were trying to do high speed conversion I would use a low offset
> > buffer to drive the inputs.  If the lines are floating, each
channel
> > will tend to report the same value as the last driven channel - it
is