[Qt-embedded-interest] Trignometric functions in qt-embedded

[Gianluca Renzi]

On Monday 20 July 2009 12:24:21 Sandeep G.R wrote:
> Hi All,
>
>           I have ported linux into S3C2410 board and i have built some
> applications in qt-3.3.7(host) which accepts values from lineedits X & Y
> the perform some calculations using sine and cosine trignometric functions
> and put the result in another lineedit Result. but i am getting correct
> result in host but not in target even i traced the output but sine and
> cosine values are wrong  please help us.
as far as I know s3c24xx SoC are fpu-less.
So floating point calculation has to be done in software (kernel enabled with 
FastFPU or similar), and your crosstool has to define fpu=softfloat or 
similar.
So for _every_ floating point calculation a kernel call is invoked, so you can 
imagine what a overhead.
It is best using a Lookup Table for sine and cosine because real time floating 
point calculations are very intensive work for a such small cpu.
google is your friend look there.

Regards,
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Gianluca Renzi
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fax: +39.0542.609212
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