On Mon, 9 Mar 1998 10:56:06 -0800, you wrote:

>Hello,
>
>Does anyone have a simple way of converting from degrees Celsius
>to degrees Fahrenheit (and vice-versa) using PIC math?
>
>C -> F
>======
>C*9/5 + 32
>
>
>F -> C
>======
>(F-32)(5/9)
>
>
>Thanks in advance!
>
>-Randie
>rohtsji@glenayre.com
A technique I used a while ago to simplify the maths when displaying a
temperature value derived from a lookup table (for a thermistor) was
to make the table entries equal to (deg.C * 4/5)+32 (lookup table
calculated from thermistor curve).
To display C you do (entry-32) * 5 >> 2
To display F you do ((entry-32) * 9 >>2) +32
This handles negative values  (remember to propagate sign in the
maths!), and the *5 and *9 multiply ops can each be done with shifts
and an add. It is also very amenable to using the same code with a
couple of conditional skips to select C or F .
     ____                                                           ____
   _/ L_/  Mike Harrison / White Wing Logic / wwl@netcomuk.co.uk  _/ L_/
 _/ W_/  Hardware & Software design / PCB Design / Consultancy  _/ W_/
/_W_/  Industrial / Computer Peripherals / Hazardous Area      /_W_/