AVR-Chat

I'm having a problem with a tiny26, the ADC values seem to be just a
little bit insane.  The chip works on another board just fine, and
only some of our boards are having the problem so, i'm thinking defect
or tolerance issue, is causing the ADC to go nuts.  Does anyone have
any insight as to things that could cause the ADC to get upset?

On Tue, Aug 23, 2005 at 03:04:21PM -0500, Michael Haisley wrote:
> I'm having a problem with a tiny26, the ADC values seem to be just a
> little bit insane.  The chip works on another board just fine, and
> only some of our boards are having the problem so, i'm thinking defect
> or tolerance issue, is causing the ADC to go nuts.  Does anyone have
> any insight as to things that could cause the ADC to get upset?

Electrical noise.

-- 
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.

On Tue, 23 Aug 2005 15:52:19 -0500, you wrote:

>On Tue, Aug 23, 2005 at 03:04:21PM -0500, Michael Haisley wrote:
>> I'm having a problem with a tiny26, the ADC values seem to be just a
>> little bit insane.  The chip works on another board just fine, and
>> only some of our boards are having the problem so, i'm thinking defect
>> or tolerance issue, is causing the ADC to go nuts.  Does anyone have
>> any insight as to things that could cause the ADC to get upset?
>
>Electrical noise.

I have seen a Tiny26 ADC do odd things if you forget to connect the analog Vdd pin, like do one good
conversion after powerup then return garbage afterwards

If there are two parallel tracks/wires on the circuit board, and those two 
are in close proximity to each other; Then it is possible, by induction, for 
a signal of one track/wire to generate an �electrical noise� on the other 
track/wire.
It might be that, on the circuit board, the track/wire leading to the 
analogue input pin of the microcontroller is picking noise from some digital 
track/wire. Hence, as mentioned before, Electrical Noise.

>On Tue, 23 Aug 2005 15:52:19 -0500, you wrote:
>
> >On Tue, Aug 23, 2005 at 03:04:21PM -0500, Michael Haisley wrote:
> >> I'm having a problem with a tiny26, the ADC values seem to be just a
> >> little bit insane.  The chip works on another board just fine, and
> >> only some of our boards are having the problem so, i'm thinking defect
> >> or tolerance issue, is causing the ADC to go nuts.  Does anyone have
> >> any insight as to things that could cause the ADC to get upset?
> >
> >Electrical noise.
>
>I have seen a Tiny26 ADC do odd things if you forget to connect the analog 
>Vdd pin, like do one good
>conversion after powerup then return garbage afterwards