Aquisition of Data from DAQStart program into matlab

Tuesday Lab

• carla_sl : Carla wiggling a mixing slider (potentiometer) in a sinusoid fashion. 2048 samples at a 512 sampling rate.

  # plotting the data in matlab:
  plot(cvi_data)
  
  # saving the data to a file
  fid = fopen('carla_sl', 'w')
  fprintf(fid, '%d\n', cvi_data)
  fclose(fid)
  

• carla_fq : Magnitude response data, frequency bins are sampling-rate / sample-count Hertz wide (2048/512 = 4 Hertz), no windowing, negative frequencies removed.

  # plotting the frequency data:
  transform = fft(cvi_data);     # complex numbers
  magnitude = abs(transform);    # magnitude of the spectrum
  dbmag = 20 * log10(magnitude); # convert to dB y-axis scale (a log scaling)
  
  dbmag = 20 * log10(abs(fft(cvi_data)));  # doing it all in one step
  
  dbmagpos = dbmag(1:1024);      # keep only positive frequencies 
                                 # from 0 Hertz to 512/2 = 256 Hertz
  
  plot(dbmagpos);
  
  # saving the data to a file
  fid = fopen('carla_fq', 'w')
  fprintf(fid, '%d\n', dbmagpos)
  fclose(fid)
  

• Here is an frequency analysis of the slider data given above.

• flexsens : flex sensor data, bending along with finger. 2048 samples at 512 sampling rate.
• flexfreq : magnitude spectrum. including negative frequencies at the end of the list. No windowing.