You don't mention how accurate or what range you need to cover. However,
here's something you might find useful:

1) Store everything to the 1/10 of 1 degree (in other words 100 deg -->
1000)
2) Display only to 1 degree (chop off last digit on output)
3) Round up (if that last digit is 5 or more, add 1 to the second to last
digit and propagate any carry).
4) Use 32 bit math

Now, given that:

F=(64C+32C+16C+2C+C)/64+320
Ctmp=F-320
C=(128Ctmp+8Ctmp+4Ctmp+2Ctmp)/256

Suppose you start with 100 deg. C:
You really store that as 1000 so:
(64(1000)+32(1000)+16(1000)+2(1000)+1000)/64+320=2116 (211.6, rounds up to
212)

Or, start with 212 deg F:
This is 2120 so Ctmp is 1800
Then:
(128(1800)+8(1800)+4(1800)+2(1800))/256 = 998 (99.8, rounds up to 100)

Of course, all of these multiplies and divides can be done using shifts.
Shift left once for *2, twice for *4, thrice for *8, etc. Shift right once
for /2, twice for /4, etc.

Then the only hard part is to convert to decimal which there are many
routines for that (mostly requiring /10). However, if you are data logging
(DAU), you may be able to push that processing to the PC (or other DMU). If
you are doing math, the error may not be significant, and you can just
rewrite your equations so they all expect 10C or 10F instead of C or F.

Does this make any sense? I'm still jet lagged, so who knows. Anyway, if I
didn't make it plain, ask me again and maybe I'll be clearer later :-)

Regards,

Al Williams
AWC
*Solderless Stamp and PIC Prototypes at http://www.al-williams.com/awce.htm
--->Pick up your FREE Basic Stamp I Simulator for Windows at the same
address.


-----Original Message-----
From: Randie Ohtsji [4555] <rohtsji@GLENVAN.GLENAYRE.COM>
Date: Monday, March 09, 1998 12:56 PM
Subject: degrees C to degrees F conversion


>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
>