I am trying to implement the IIR Butter-worth filter using CMSIS library.. please refer this www.docdroid.net/.../iir.txt.html to verify the code i took the input buffer/array of 1's and i obtained the output.. i copied the output to MATLAB and implemented FFT on that.. the answer is different from the input i.e 1's.. Is there any mistake in my code? am i doing any mistake in cross verification of the program?