manchester2bin(inputData)

function decodedData = manchester2bin(inputData)
%   MANCHESTER2BIN(inputData) decodes a manchester serial
%   sequence to its corresponding binary value.
%
%   Decoding is done according to G.E. Thomas' convention 
%   (high-to-low '01' = '1', low-to-high '10'= 0), assuming LSB first
%   transmission.
%
%   Syntax: decodedData = MANCHESTER2BIN(inputData) 
%
%   Where:
%   inputData   =    string with binary values which length must be EVEN,
%                    with the MSB at at the left-most position (index = 1)
%   decodedData =    string with binary values which length is half of
%                    inputData with the MSB at the left-most position
%
%   If the inputData sequence is not a valid manchester code MANCHESTER2BIN
%   will return an empty string. 
%
%   Example: 
%       >>decodedData = manchester2bin('01011010')
%       
%       decodedData =
%       1100
%
%   Other m-files required: none
%   Subfunctions: none
%   MAT-files required: none
%
%   Author: Robert Brookhuis
%   email: r.a.brookhuis(at)gmail.com 
%   MAR 2009; Last revision: 02-Mar-2009

nBits = length(inputData); % length of inputData

% preallocate decodedData as array of doubles, for speed. Faster than
% handling strings. Array is converted to string after decoding. 
decodedData = ones(1,nBits/2); 

if mod(nBits,2)~=0 % check if array is even, otherwise generate error
    error('Length of array must be even')
end

for i = nBits:-2:2 % count from max. size downwards with steps of 2
    if inputData(i) ~= inputData(i-1) % if bits are unequal
        decodedData(i/2) = inputData(i); % the first bit is the binary value
    else
        decodedData = []; %if bits are equal, it's not manchester code 
        break %exit for loop
    end
end

decodedData = char(decodedData); %cast decodedData back to string