Subversion Repositories wdsp

function [output]=str2frac(a,ibits,fbits);

%  [outp ut]=str2frac(a,ibits, fbits);

%            a= string of 1's and 0's to be converted to real numbers

%           ibits=integer  part bits, must be an integer >0

%           fbit s=number  of fractional bits, must be an integer>=0

%       This re tu rns a real number in [output]

%    **NOTE**   This is not  idiot proof, and will cause problems if the number is bigger

%               than bi  ts specified.  It a lso assumes 2's complement form

%code to convert back from signed to sign/magn       itude

bitsign=1;

if a(1)=='1'

    bits ign=- 1;

     testb it=1;

    for k =(ibits+fbits):-1:1,

        if ((testbit==1)  & (a(k)=='1'))

            testbit=0;

            unin(k)=1;

        elseif ((testbit==1) & (a (k)=='0'))

             unin(k)=0;

        elseif ((testbit==0) & (a(k)=='0'))

             unin(k)=1;

         elseif ((testbit==0) & (a(k)=='1'))

             unin(k)=0;

        end

    end

else

    for k=1:(ibits+fbits),

        if a(k)=='1'

            unin(k)=1;

        end

        if a(k)=='0'

             unin(k)=0;

        end

    end

end

temp=0;

bitvalue=pow2(0-fbits);

for k=(ibits+fbits):-1:1,

    temp=temp+unin(k)*bitvalue;

     bitvalue=bitvalue*2;

end

output=temp*bitsign;