function ds = read_syncdata(data_files)
  % settings
  %DATASET_DIR = 'test_20221';
  TS_FILE_EXT = 'ts';
  %SAMPLE_FILE_PREFIX = 'ch_';
  SAMPLE_FILE_EXT = 'dat';
  %CHANNELS = 2;

  %for ch=0:1:(CHANNELS-1)
  %  FN_SAMPLE{ch+1} = strcat(data_files, '/', SAMPLE_FILE_PREFIX, num2str(ch), '.', SAMPLE_FILE_EXT);
  %end

  [files_n,~] = size(data_files);
  
  s = [];
  ts = [];
  
  for i=1:files_n
    
    data_file = data_files(i,:);
    
    % load timestamps
    FN_TS = strcat(data_file, '.', TS_FILE_EXT);
    f = fopen(FN_TS ,'r');
    d = fread(f,[2,Inf],'uint32');
    fclose(f);

    % create fractional timestamp
    d = d(1,:) + d(2,:) / 1E+09;
    
    ts = [ts; d];

    % get sample count
    %sample_cnt = length(ts);

    % load samples
    FN_SAMPLE = strcat(data_file, '.', SAMPLE_FILE_EXT);
    f = fopen(FN_SAMPLE,'r');
    d = fread(f, [1,Inf],'int16');
    s = [s; d];
    fclose(f);
  end
  
  %figure(1)
  %plot(ts(1,1:100), s(1,1:100), 'x')
  %xlim([ts(1) ts(100)])
  %hold on
  
  ds = [ts' s'];
end