AR1100 Datasheet, PDF (29/58 Pages) Microchip Technology – AR1100 Resistive USB and RS-232 Touch Screen Controller

AR1100 RESISTIVE USB AND RS-232 TOUCH SCREEN CONTROLLER
7.0 OPERATION
7.1 Configuration
The AR1100 is operational out of the box using factory
defaults. Some applications may have special needs
that require changes to those factory settings (parame-
ter registers). This is easily accomplished using the
commands described in Section 5.0, Commands. The
recommended procedure is as follows:
1. Issue command: TOUCH_DISABLE (disables
touch reports so as not to interfere)
2. Issue command: REG_WRITE, as needed, to
modify the value of selected parameter registers
3. Issue command: EE_WRITE_PARAMS (optional)
to archive new register values as ‘defaults’
4. Issue command: TOUCH_ENABLE (to re-enable
touch reports)
Note:
Configuration commands are supported
only in UART and HID-GENERIC
communication modes. Refer to
Section 7.6, USB Mode Change.
7.2 Calibration
7.2.1 INTRODUCTION
Calibration enables the AR1100 to issue touch reports
that (1) correct/modify sensor orientation and (2) pre-
cisely map the reported touch location to the physical
dimensions of the underlying display device. The
AR1100 has the option of either reporting RAW touch
reports or utilizing calibration information to report CAL-
IBRATED touch reports. Configuration register,
“TouchOption”, contains bit flag “CALE” (calibration
enable) to choose between the two.
The calibration process requires the operator to
sequentially touch a series of targets [crosshairs] pre-
sented by the host on the display device. The AR1100
archives the raw-touch data from each calibration
touch point in EEPROM, then uses that data in normal
operation to process “raw” data into “calibrated” data.
Note:
Calibration is supported only in UART and
HID-GENERIC communication modes.
Refer to Section 7.6, USB Mode Change.
7.2.2
CONFIGURATION
Both the host and device must know/understand the
geometry of the calibration point matrix. The AR1100
defines the matrix by (1) an INSET and (2) calibration
TYPE i.e., number of points (4, 9 or 25). The TYPE is
set by the argument of the calibration command. The
INSET is pre-defined by the Configuration register
CalibrationInset.
The INSET is predefined as ‘64’ – interpreted as 64/
256 (i.e., 25%) of the sensor width or height. This
defines the ‘margin’ on the perimeter of the calibration
point matrix. Interior calibration points are spaced
equally between the margins (e.g., for the 9-point cali-
bration in the illustration – point 2 is half-way between
points 1 and 3). See Figure 7-1.
FIGURE 7-1:
CALIBRATION POINT LAYOUT
 2011 Microchip Technology Inc.
DS41606B-page 29