anchor.diff:       0 swap 0           ( caddr 0 u 0 )
        ?do
                           ( caddr u32 )
  -        i 3 and >r
           over i + c@     ( caddr u32 byte )
  -        r@ 3 lshift lshift or
  +        i 3 and dup >r
  +        3 lshift lshift or
           r> 3 = if
               >gd
               0
  
positive.code: 
  : GD.calibrate  \ run the FT800's interactive calibration procedure
      GD.Clear
      240 100 30 GD.OPT_CENTERX s" please tap on the dot" GD.cmd_text 
      GD.cmd_calibrate
      GD.finish
      GD.cmd_dlstart
  
negative.code:     000 hostcmd         \ ACTIVE
  
      custom @ execute
  ;
  
  : common-init
  