/**
  \example profile3.cpp 

  This sketch shows how to assign time to a custom category in the
  profiling system.  There are three categories reserved for sketch
  use: #TICKER_SKETCH0, #TICKER_SKETCH1, and #TICKER_SKETCH2; here we
  use just the first.  

  Calls on SFBTicker::pushTime(u32) and SFBTicker::popTime() must be
  properly matched, as in this sketch.  (Be careful if you have \c
  return statements buried in the middle of functions!)

  Typical output from this sketch in response to 'p' packets:
  <pre>
    p
    Ln 29.598 BG=89.28 SI=0.01 OI=1.60 PH=0.04 AH=0.34 S0=8.71
    p
    Ln 46.299 BG=89.30 SI=0.01 OI=1.60 PH=0.03 AH=0.34 S0=8.70
  </pre>
  showing that over 8% of the time is now assigned to our 'sketch 0'
  category, while background still gets nearly 90%.

 */
