Re: [Paparazzi-devel] Incorrect Battery Level

[Felix Ruess]

Hi Reto,

by default the scaling factor for the tiny2.11 is defined in
conf/autopilot/tiny_2_1_1.h:
#define DefaultVoltageOfAdc(adc) (0.0247311828*adc)

This factor can be computed like this:
      reference_voltage / adc_max_value * (R1 + R2)/R2
R1 and R2 make up the voltage divider to measure Vbat.
So for the Tiny2.11 we have
      3.3/1023 * 11.5/1.5 = 0.0247311828

So maybe you have different values for R1 (10k) and R2 (1.5k)?
Due to the tolerance of the resistors the factor will be slightly different....
If you want to be precise you might want to set this factor a for your
specific board in your airframe file as you did.

Cheers, Felix

On Sat, Sep 25, 2010 at 4:08 PM, Reto Büttner <address@hidden> wrote:
> Hi all,
>
> I am configuring a new fixed wing airframe and don't get the battery
> level reading correct. The GCS outputs 5.4 volts although the correct
> voltage is 7.4V on my LiPo 2S. I am running a Tiny 2.11 and think I
> have configured that correctly in the airframe file:
>
> target name="ap" board="tiny_2.11"
>
> I have read the posts in the mailing list archive. If I use the
> standard configuration the battery level is at 5.4V. I tried
> configuring it myself in the airframe file using lines like:
>
> <define name="VoltageOfAdc(adc)" value ="(0.03703*adc)"/>
>
> This changes the battery level reading, but I can't it right. Can someone 
> help?
>
> Thanks in advance!
>
> Reto
>
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