Specifications

78 Chapter 6 - Command Reference
controller. This will interrupt the sequence and an Acknowledge packet will be
returned with a "calibration terminated" warning.
Host-Driven Calibration Sequence
Alternatively, a host-driven calibration sequence may be performed. It must first
disable the Calibration and Scaling Modes, acquire the low and high calibration
points, transmit them to the controller with the CX and CY commands, then
restore the modes. Host-driven calibration sequences are more flexible in that
calibration points can be extrapolated to the edges, multiple samples acquired and
averaged, etc. For an example of a host-driven calibration sequence, see
EXAMPLE2.C, page 60.
Z-Axis Calibration
Z-axis calibration is typically not required as no Z data is available with resistive
touchscreens. The controller defaults to 0-255, but always returns the HighPoint
value.
Setting or Querying the Swap Axes Flag
Swapped axes can be detected by a three-point host-driven calibration sequence.
This can correct inverted cabling or touchscreens rotated 90°. If the coordinates of
the third corner change in what should be the constant axis, then the axes are
swapped. The controller can then be informed to swap the axes through the Swap
Axes Flag. See EXAMPLE2.C, page 60.
Enable is a byte value where the least significant bit is 1 to swap axes or 0 for
normal operation.
Calibration and Axis Swapping are disabled by factory default.