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

From: Larry Barello
Subject: Re: [avr-gcc-list] Troubles with ADC on ATMega16
Date: Thu, 8 May 2003 16:22:43 -0700

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?


----- 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
> 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
> > capacitor to filter the input signal.  I am never chasing high
> > signals so I just jammed a large capacitor to clean things up.  If
> > were trying to do high speed conversion I would use a low offset
> > buffer to drive the inputs.  If the lines are floating, each
> > will tend to report the same value as the last driven channel - it

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