AVR-Chat

The values are truly random. They seem to sway sometimes to one sign or 
the other, but typically it is distributed negative and positive 
equally. There is no biasing error because whichever axis is connected 
to ADC input 3 (0 being the first input) is fine. The biased, still 
value is always zero. I haven't had the chance to check the rest of the 
ADC, but I feel that the first half of the ADC is operating well, while 
the other half is exhibiting some sort of problem. Are there any 
pull-up/down settings? Port A on the Atmega 32 has no other alternate 
function besides ADC input, but perhaps there is something I am missing.

I do have access to the scope, and the signal looks clean to me. 
Furthermore, when I switch the two channels and axes, the error is 
pertinent to the input channel of the ADC, and not the output of the sensor

Thanks.
Gustavo Goretkin

Andreas Stemmer wrote:
>
> Gustavo Goretkin wrote:
> > After I average 3 and 4's values for a while to get the bias of the
> > accelerometer's outputs, 3 always returns a value of zero (after
> > removing the bias and having the sensor still), but 4 always returns
> > some random value that is anywhere from 15-30 ADC units off. I have
> > switched the sensor configuration (swapped 3 and 4), and still 4
> > returns non-ideal values and 3 is fine.
>
> Is the "random value" always off in the same direction or is it really
> random? In the first case I suspect some error in the way you're
> removing the bias. In the latter case, it looks like you have too much
> noise, so a check of the signal preparation circuitry would perhaps
> reveal something. Do you have access to a scope?
>
> AS
>
>