Conversion from fixed point to floating point and vise versa

[alzomor]

convert fixed point to floating point

Asslamo 3likom

How to convert from fixed point Q15 to floating point and vise versa in C

Salam
Hossam Alzomor
www(.)i-g(.)org

 

[btbass]

convert fixed point to float

If you are using Microchip Mplab C30 compiler, if you look in the header file, 'dsp.h' you will find the following functon prototypes:

extern fractional Float2Fract (         /* Converts float into fractional */
   float aVal                           /* float value in range [-1, 1) */
);
extern float Fract2Float (        /* Converts fractional into float */
   fractional aVal                /* fract value in range {-1, 1-2^-15} */
);

You will find the functions in the dsp\src directory.

 

[alzomor]

fixed point to float

Thanks btbass

But My question is How it can be implemented in C.
I am not using Mplab C30 compiler

Salam
Hossam Alzomor
www(.)i-g(.)org

 

[btbass]

q15 conversion

Here are the functions in C from the Microchip lib.

 

[alzomor]

fixed to float conversion

Hi

A Good and simple way to:
Convert from Fixed point to Flaoting point.
Just divide by the full scale of integer represented in the no of bits representing fixed point and type cast the result to float
example
a: fixed point represented in Q15 formate
b:floating point representation of a

b= (float) (a/(2^15-1))

Conversion from float to fixed:
a=(int) (b*(scale))
scale depends on the max value of floating point values being converted and fixed point formate result.



Salam
Hossam Alzomor