about vhdl code for cic interpolation filter

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G = (2^(2*N-1)*(R*M)^(i-N))/R;

should be according to Hogenauer

G = (2^(2*N-i)*(R*M)^(i-N))/R;

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Thanks FvM.

That makes sense now, just a typing error from doc to doc.

new code(final??):

Bin = 8; %input width

N = 4; %stages of comb or integrator

M = 2; %differential delay

R = 512; %interpolation rate

%cic decimator at any stage

Bout = N * log2(R*M) + Bin;

%cic interpolator per ith stage

%stages 1~N

for i = 1:N

G = 2^i;

Bout = Bin + log2(G);

d(i) = Bout;

end

%N+1 ~ 2N stages

for i = N+1:N*2

G = 2^(2*N-i)*(R*M)^(i-N)/R;

Bout = Bin + log2(G);

d(i) = Bout;

end

for i = 1:N*2

fprintf('%i %i\r',i,d(i));

end