Newbie in understanding Fixed point. All I was trying to do is to begin experimenting with proportional controller. Tried first with floating. Input range is -1.0 to +1.0 , assigned Kp=1.2 and hooked these values in simulink and got the results. The output is somewhere 0.55.

Now tried with fixed point, input is -32767 to +32767 (Q15), converted Kp=1.2*32767= 39320. Hooked these values back into simulink and I am getting output close to input and not half as I got with floating. What Am I doing wrong?