Larry,

Thanks for your help !! Your 3rd degree polynomial helped me
a lot...
BTW, i think to try to change the PIC17 routine Pow to use
with PIC16... What do you think about it ?? Is it a good
ideia ??

Thanks for your help !!

[]4s
Jeferson Martin

> - -----Mensagem original-----
> De: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]Em nome de Larry Bradley
> Enviada em: quinta-feira, 9 de janeiro de 2003 19:33
> Para: PICLIST@MITVMA.MIT.EDU
> Assunto: Re: Floating Point Math Routine (Pow) for PIC16
>
>
> OK, here are two 3rd degree polynomials to approximate y=x^0
190255,
> where
> x is P/P1 in your case.
>
> I have assumed that 100<= P<= 1200. P1 is always < P, thus t
he lowest
> value
> for x will be 100/1200 = 0.0833.
>
> I generated a table of y=x^.190255 for 0.08<=x<=1.0. As in m
y case,
> it was
> necessary to split the data into two ranges to get a good fi
t.  Thus
> we get
>
> For 0.08<=x<=0.3:
>
> y=0.48093+2.12405x-5.51251x^2+6.42179x^3
>
> and for 0.3<=x<=1:
>
> y = .612857+.763474x-.569529x^2+.193612x^3
>
> Thus select a poly based on the pressure ratio P/P1 and eval
uate it,
> and
> then evaluate the rest of the function to find the altitude.
>
> Larry
>
>
> At 12:13 PM 1/9/2003 +0000, you wrote:
> >Hello Larry, it4s my case. I need to calculate the follow e
q:
> >(p/p1)
^0.190255, p and p1 are variables. Can you explain how i can
> >do it ? I need to use PIC16 due to PIC17 be very large. I h
ave
> >already downloaded the stadard FP routines (+,-
,...) from Microchip
> >site, but i don4t know how i can use it to calculate the po
w
> >function.
> >
> >Thanks a lot!
> >
> >[]4s
> >Jeferson Martin
> >
> >Larry Bradley <lhbradley@IGS.NET> escreveu:
> >
> > > There are two  appnotes. One is the basic add, subtract
stuff,
> > > the other (AN660) is for the power, log, etc. It is a lo
t of code
> > > -
 the power function requires some of the others, as I recall.
> > >
> > > I needed a power function for the system I'm working on
- The
> > > exponent in my case is a constant (y=x^0.386), so I fit
a 3rd
> > > degree polynomial to the curve, and used that and the st
andard FP
> > > routines. If the exponent is a variable, of course, you
can't do
> > > that.
> > >
> > > Larry
> > >
> > > At 10:31 AM 1/9/2003 +0000, you wrote:
> > > >Yeah, but not a POW floating point routine for PIC16, o
nly
> > > >for PIC17. I really need for PIC16 family. I had not se
en
> > > >any POW floating point routine on the Microchip web sit
e
> > > >for PIC16...
> > > >
> > > >Thanks....
> > > >
> > > >[]4s
> > > >Jeferson Martin
> > > >
> > > >
> > > >Larry Bradley <lhbradley@IGS.NET> escreveu:
> > > >
> > > > > There are floating point routines on the Microchip w
eb site.
> > > > >
> > > > > At 09:52 AM 1/9/2003 +0000, you wrote:
> > > > > >Hello,
> > > > > >
> > > > > >Please, does anyone know where i can find a floatin
g point
> > > > > >routine in assembly for PIC16 family ? I need the P
OW
> > > > > >routine with a precision of 32 bits.
> > > > > >
> > > > > >Thanks.
> > > > > >
> > > > > >[]4s
> > > > > >Jeferson Martin
> > > > > >
> > > > > >--
> > > > > >http://www.piclist.com hint: The PICList is archive
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es for
> > > > > >details.
> > > > >
> > > > > Larry Bradley
> > > > > Orleans (Ottawa), Ontario, CANADA
> > > > >
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 three
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> > > >
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> > > Larry Bradley
> > > Orleans (Ottawa), Ontario, CANADA
> > >
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> >
> >
> >
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> Larry Bradley
> Orleans (Ottawa), Ontario, CANADA
>
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