Add a ducumentation on how to calibrate the sensor

[Exeu]

Hi,

i don't know, but i think it would be beneficial to have a small guide how calibration can be done. I think there are more or less some default configs in the BLE-FW but currently it is not clear to me how to get the values for instance for the coeffs.

First of all where i can configure those Coeffs? I found one place in an overlay-file.

The values i got are times 1000 yes, but how you got those values? There are some negative values aswell. I am a bit lost in trying to interpret them somehow ^^

Furthermore i would like to determine my own coeffs - Because i think those will depend on each board setup slightly.

Thank you