AVR-Chat

On Sat, 08 Sep 2007 03:11:18 -0400
 Gustavo Goretkin <gustavo@goretkin.com> wrote:
> Hi,
>  I'm running some code on an ATMega32 (PDIP, 16mHz) I'm
> using 4 of the 8 
> ADC channels to collect data from sensors (gyros and
> accelerometers). 
> These are channels 1,2,3,4 (channels from 0-7). I am, in
> reality, using 
> only channel 1,3,4 (plan to add a sensor connected to 2
> soon). Channels 
> 1 and 3 receive very accurate data, but for some reason
> channel 4's data 
> is always off. For example, I'm using a two-axis accel.
> connected to 
> channels 3 and 4. 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. I have read of
> problems on the 
> ATMega 128 with JTAG on the first four pins of Port A,
> but Port A's 
> alternate function on the ATMega 32 is ADC only. Is there
> something I am 
> missing?
> 
> Thanks.
> Gustavo Goretkin

Is the axis with steady signal the Z axis, perhaps? If it
is, you are just measuring gravity?

Jim

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