AR1011T-ISLASHSS datasheet(35/61 Pages) MICROCHIP

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 2009-2016 Microchip Technology Inc.

DS40001393C-page 35

AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER

9.3.4.3

Calibration Data Encoded and

Stored in EEPROM

System integrators may prefer to preload a calibration

into their design. This allows the user to properly

navigate to the calibration routine icon or shortcut

without the use of a mouse. This also addresses the

need to calibrate each system individually before

deploying it to the field.

The raw touch coordinates, decoded by the controller,

for each of the four calibration touches are extrapolated

if CalibrationInset was non-zero. The four coordinate

pairs are then re-oriented, if required, such that the

upper left corner is the minimum (X,Y) “origin” value

pair and the lower right corner is the maximum (X,Y)

value pair.

Coordinates are 10-bit significant values, scaled to

16-bit and stored in a High (Hi) and Low (Lo) byte pair.

Decode the above data to as follows:

Swap the order of stored low and high bytes for

a given coordinate.

Convert the 16-bit value (stored high and low

bytes) from hexadecimal to decimal.

Divide the result by 64 to properly rescale the

16-bit stored value back to a 10-bit significant

coordinate.

Example of Low = 0x40 and High = 0xF3:

Swap:

0xF340

Hex to Decimal: 62272

Divide by 64:

973

For storing desired calibration values to the EEPROM:

• AR1010/AR1020 (See Section 9.3.12 “EEPROM

Map”

• AR1011/AR1021 (See Section 9.3.12 “EEPROM

Map”

and Section 10.2 “AR1011/AR1021 Stor-

ing Default Calibration Values to EEPROM”

Separator Upper Left (Node 1) Upper Right (Node 2) Lower Right (Node 3)

Lower Left (Node 4)

Flip State

FLIP STATE BYTE

U-0

R/W

—

XYFLIP

XFLIP

YFLIP

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

bit 7-3

Unimplemented

: Read as ‘0’

bit 2

XYFLIP:

X and Y Axis Flip bit

= X and Y axis are flipped

= X an Y axis are not flipped

bit 1

XFLIP:

X-Axis Flip bit

= X-axis flipped

= X-axis not flipped

bit 0

YFLIP:

Y-Axis Flip bit

= Y-axis flipped

= Y-axis not flipped

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