Hi, im trying to build a thermometer with an 8051 controller, i have a simple ramp adc that converts the resistance from a NTC-resistor to a 16bit integer, but i ran in to some problem.

The resistance/temperature equation for a NTC is: R = A * e^(B / t)
A and B are material constants, t is the temperature, R is the resistance
To calculate a temperature from a given resistance i think the equation can be rewritten like this: t = B / ln(R / A)

But how should i do a ln() with 8051, or are there any easier way to get the temperature ?