MATLAB CIC Moving Average Filter

CICFilter.m

function output = CICFilter(input)

% Asserts
assert(isa(input, 'double') && ~isreal(input) && all(size(input) == [80*100,1]))

persistent lastInputs lastOutput

numTaps = 16;

% Initialize History
if isempty(lastInputs) || isempty(lastOutput)
    lastInputs = complex(zeros(numTaps,1));
    lastOutput = complex(0);
end

output = coder.nullcopy(complex(zeros(size(input))));

for x = 1:length(input)
    
    %output[n] = output[n-1] + input[n] - input[n-taps]
    if (x-numTaps)>0
        output(x) = output(x-1) + input(x) - input(x-numTaps);
    elseif (x==1)
        output(x) = lastOutput + input(x) - lastInputs(x);
    else
        output(x) = output(x-1) + input(x) - lastInputs(x);
    end
    
end


% Save history for next call
lastOutput = output(end);
lastInputs(1:numTaps) = input(end-numTaps+1:end);

end