If you only need modest precision, a lookup table might be your best
bet.

> ----------
> From:         Aaron Hickman[SMTP:hickmaab@DUNX1.OCS.DREXEL.EDU]
> Reply To:     pic microcontroller discussion list
> Sent:         Thursday, December 11, 1997 2:37 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      logarithmic calc
>
> Good evening,
>
>         Can anyone point me in the direction of an example showing the
> implementation of a logarithmic calculation on the PIC16C84.  I am
> trying
> to convert a voltage (1.5-8.7 volts) from a vacuum gauge into a
> pressure
> in Torr using the relationship (P=10^(V-11.00).  Any help/suggestions
> will be greatly appreciated.
>
> Sincerely,
> Aaron Hickman
>