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.