AR1000_16 Datasheet, PDF (41/61 Pages) Microchip Technology – AR1000 Series Resistive Touch Screen Controller

AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
10.2 AR1011/AR1021 Storing Default
Calibration Values to EEPROM
If you wish to implement fixed calibration values,
preloaded into the AR1000 EEPROM, then the
following procedure must be followed (See
Section 10.2.1 “Preparation for Fixed Calibration
Values”).
10.2.1
PREPARATION FOR FIXED
CALIBRATION VALUES
Determine if fixed calibration values are suitable for
your application and determine your desired values.
Calculate a checksum for your custom data set. See
Section 9.3.4.3 “Calibration Data Encoded and
Stored in EEPROM” for additional details regarding
calibration data format.
An example of calculating the checksum is shown
below (See Table 10-1).
TABLE 10-1: CHECKSUM CALCULATION EXAMPLE
Description
Value
Seed
Block Key
Upper Left
Upper Left
Upper Left
Upper Left
Upper Right
Upper Right
Upper Right
Upper Right
Lower Right
Lower Right
Lower Right
Lower Right
Lower Left
Lower Left
Lower Left
Lower Left
Flip State
X
Low byte
X
High byte
Y
Low byte
Y
High byte
X
Low byte
X
High byte
Y
Low byte
Y
High byte
X
Low byte
X
High byte
Y
Low byte
Y
High byte
X
Low byte
X
High byte
Y
Low byte
Y
High byte
0x45
0x55
0x06
0x1B
0xA5
0x08
0x13
0xDF
0xF4
0x0B
0x98
0xE4
0x1E
0xEC
0xBF
0x1A
0x32
0xE7
0x01
Checksum
The Checksum is an 8-bit value calculated by
successive additions with overflow ignored, as shown
below.
Checksum = 0x45
For each of the 18 calibration values, starting at the
Block Key and ending with the Flip State
Checksum += Calibration value
Next Calibration value
Operation
n/a
0x45 + 0x55 =
0x9A + 0x06 =
0xA0 + 0x1B =
0xBB + 0xA5 =
0x60 + 0x08 =
0x68 + 0x13 =
0x7B + 0xDF =
0x5A + 0xF4 =
0x4E + 0x0B =
0x59 + 0x98 =
0xF1 + 0xE4 =
0xD5 + 0x1E =
0xF3 + 0xEC =
0xDF + 0xBF =
0x9E + 0x1A =
0xB8 + 0x32 =
0xEA + 0xE7 =
0xD1 + 0x01 =
Checksum Result
0x45
0x9A
0xA0
0xBB
0x60
0x68
0x7B
0x5A
0x4E
0x59
0xF1
0xD5
0xF3
0xDF
0x9E
0xB8
0xEA
0xD1
0xD2
0xD2
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DS40001393C-page 41