Ultimately, you need to figure out where the doubles are creeping in; what is the first signal or value in your dataflow that is a double in Simulink? This will get emitted as a real. Looking at your code, you have a lot of constants embedded in it; recall that in MATLAB code all data is by default a double. So, you need to type your constants, which will entail learning about fixed point typing, since you are trying to divide by decimal values. Type "web(fullfile(docroot, 'fixedpoint/index.html'))" to access the fixed point help.
Typed constants may look something like:
fi(1.4, 0, 8, -5)
uint8(0)
The input and output data types to your function can be set via the Model Explorer (Tools->Model Explorer via menu, or ^H in the model diagram).
The final problem you will run into is your use of the division "/" operator. In general this is not synthesizable. If you intend to synthesize your design you will need to replace this with some other numeric operation. Since you are dividing by a constant you can change the divisions into multiplies by the reciprocal values.
