AVR-Chat

How have you supplied AVcc? What are you using for reference? Does the reference have a bypass capacitor?

Jim Wagner
Oregon Research Electronics
On Oct 26, 2012, at 8:03 AM, Dave McLaughlin wrote:

> Hi all,
> 
> I have an ATMEGA32 and I am using the ADC to measure the power supply that
> is connected to the device.
> 
> Having done a similar thing with other processors, I am stumped by what I am
> seeing with the AVR device.
> 
> I have a potential divider on the input so that I can measure up to +32V
> 
> I have a 10K resistor to ground with a 56K resistor in series with the +
> supply I want to monitor. The ADC in the datasheet suggest an input
> resistance of 10K is the ideal load.
> 
> When I measure and do a calibration of the ADC at +24V I get a good reading.
> I now set the supply to +12 and I get a reading of +1V above this.
> 
> I am busy taking readings to see if the readings are linear.
> 
> The ADC ref is a nice clean +5V from the supply (I am assuming ratiometric
> on my design)
> 
> Has anyone any clues to why I am seeing this from the ADC?
> 
> Cheers
> 
> Dave.
> 
> ---
> 
> Very funny Scotty, now beam down my clothes.
> 
> ---
> 
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> 
> 



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