SV: SV: [Icc-avr] ATmega8 hardware problem

[Bengt Ragnemalm]

The comparator should not be the problem. Enabling the pull-up may screw
that comparator if you are measuring high impedance sources but I do not
think it should disable the pull-ups. Let us know in the future what you may
find.

If you can disable the source of the signal you can just take a ohm-meter
and measure the value of your pull-up in different situations like with and
without AC and with or without internal pull-ups.

/Bengt

> -----Ursprungligt meddelande-----
> Från: icc-avr-bounces at imagecraft.com [mailto:icc-avr-
> bounces at imagecraft.com] För John Baraclough
> Skickat: den 18 augusti 2008 11:13
> Till: benra at imt.liu.se; Discussion list for ICCAVR and ICCtiny Users. You
> do NOT need tosubscribe to icc-announce if you are a member of this.
> Ämne: Re: SV: [Icc-avr] ATmega8 hardware problem
> 
> Yes, I already searched the data sheet to no avail. It has been
> suggested on AvrFreaks that the Analog Comparator being active (which is
> the default state) may be the cause. Unfortunately I now have external
> pull-ups added, so I can't see if disabling this will help. However I
> will come back to this once the current project is finished and let you
> know what I find.
> 
> All the best for now,
> John
> 
> 
> Bengt Ragnemalm wrote:
> > I we assume that you have defined the registers correctly for turning
> the
> > pull-ups (the corresponding bit in PORTD shall be set) on I would take a
> > search in the entire datasheet for the word "pull-up". Check the the
> > secondary function of the PORT D pins. Some functions may turn pull-ups
> off.
> > Or it could be that the internal value are to high (up to 50k).
> >
> > Also check the status of the PUD bit in SFIOR at the time you use PORTD
> >
> > Or it could be that the AVR is damaged.
> >
> > /Bengt
> >
> 
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