update

Last night I spend an hour trying to fix the remaining problems.

Capacitor has been changed. Linearity is now ok.

Compensation in software works. The correct multiplication value has to be determened.

Software has strange behavior. I have to configure ports to input repeatately.
If I don't the read values are incorrect. It probably generated fasle interrupts too. I'll check some example programs to see if this is a known problem. It may be a problem related to foating inputs.