DS41393A-Page 16

© 2009 Microchip Technology, Inc.

7.12.11 TouchOptions Register (offset 0x0D)

The TouchOptions register contains various “touch” related option bits.

R = Readable bit, W = Writable bit, U = Unimplemented bit read as ‘0’

U–0

U–0

U–0

U–0

U–0

U–0

R/W

R/W

–

–

–

–

–

–

48W

CCE

Bit 7

Bit 0

bit 7-2 Unimplemented: Read as ‘0’

bit 1

48W:

4-wire or 8-wire Sensor Selection bit

1 = Selects 8-wire sensor operating mode

0 = Selects 4-wire sensor operating mode

bit 0

CCE:

Calibrated Coordinates Enable bit

1 = Enables calibrated coordinates, if the controller has been calibrated

0 = Disables calibrated coordinates

A 4-wire touch sensor will not work if the 48W configuration bit is incorrectly defined as one, which

selects 8-wire.

An 8-wire touch sensor will provide basic operation if the 48W configuration bit is incorrectly defined

as zero, which selects 4-wire. However, the benefit of the 8-wire sensor will only be realized, if the

48W

configuration bit is correctly defined as one, selecting 8-wire.

7.12.12 CalibrationInset Register (offset 0x0E)

The CalibrationInset register defines the expected position of the calibration points, inset from the perimeter of the

touch sensor’s active area, by a percentage of the full scale dimension.

This allows for the calibration targets to be placed inset from edge to make it easier for a user to touch them.

The CalibrationInset register value is only used when the Calibration Mode command is issued to the controller.

In Calibration Mode, the controller will extrapolate the calibration point touch report values by the defined

CalibrationInset percentage to achieve full scale.

A software application that issues the Calibration Mode command must present the displayed calibration targets

at the same inset percentage as defined in this CalibrationInset register.

Valid values are as follows.

0 ≤ CalibrationInset ≤ 40

Calibration Inset = ( CalibrationInset / 2 ) % , Range of 0–20% with 0.5% resolution

For example, CalibrationInset = 25 (0x19) yields a calibration inset of (25 / 2) or 12.5%. During the calibration

procedure, the controller will internally extrapolate the calibration point touch values in Calibration Mode by 12.5%

to achieve full scale.

12.5% of

Full Scale

12.5% of

Full Scale

Location of calibration

targets presented

during calibration.