One way to get started may be to wrap the ultrasonic sensor code in a function, and call that function from a Simulink MatlabFunction block, using coder.extrinsic. The MatlabFunction block in Simulink would look something like
function out = MatlabFuntion(in)
coder.extrinsic('ultrasonic_sensor');
% do stuff here, create inputs for ultrasonic_sensor
outputs = ultrasonic_sensor(inputs);
% do stuff here, process outputs from ultrasonic_sensor
end
