anchor.diff:  \ These registers are not used often
   \ 302104 1024f0 gdconst GD.REG_TOUCH_MODE
   \ 302114 102500 gdconst GD.REG_TOUCH_OVERSAMPLE
  +\ 302108 1024f4 gdconst GD.REG_TOUCH_ADC_MODE
  +\ 30210c 1024f8 gdconst GD.REG_TOUCH_CHARGE
  +\ 302110 1024fc gdconst GD.REG_TOUCH_SETTLE
   \ 00000001 constant GD.CTOUCH_MODE_COMPATIBILITY
   \ 00000000 constant GD.CTOUCH_MODE_EXTENDED
   
  
positive.code: 30207c 102478 gdconst GD.REG_TAG
  302074 102470 gdconst GD.REG_TAG_X
  302078 102474 gdconst GD.REG_TAG_Y
  302108 1024f4 gdconst GD.REG_TOUCH_ADC_MODE
  30210c 1024f8 gdconst GD.REG_TOUCH_CHARGE
  30218c 102574 gdconst GD.REG_TOUCH_DIRECT_XY
  302190 102578 gdconst GD.REG_TOUCH_DIRECT_Z1Z2
  30211c 102508 gdconst GD.REG_TOUCH_RAW_XY
  302120 10250c gdconst GD.REG_TOUCH_RZ
  302118 102504 gdconst GD.REG_TOUCH_RZTHRESH
  302124 102510 gdconst GD.REG_TOUCH_SCREEN_XY
  302110 1024fc gdconst GD.REG_TOUCH_SETTLE
  30212c 102518 gdconst GD.REG_TOUCH_TAG
  302128 102514 gdconst GD.REG_TOUCH_TAG_XY
  302150 10251c gdconst GD.REG_TOUCH_TRANSFORM_A
  
negative.code:     gd2-unsel
  ;
  
  : hostcmd2 ( u0 u1 -- )
      gd2-sel
      swap >spi
      >spi
      00 >spi
      gd2-unsel
      60 ms
  ;
  
  : hostcmd
      0 hostcmd2
  ;
  
  : measureF ( -- u ) \ measure FT800's actual clock frequency
  