WM9712L datasheet(42/77 Pages) WOLFSON

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WM9712L

Production Data

PD Rev 4.5 August 2006

CONTROLLING THE TOUCHPANEL DIGITISER

All touchpanel functions are accessed and controlled through the AC-Link interface.

PHYSICAL CHARACTERISTICS

The physical characteristics of the touchpanel interface are controlled through register 78, as shown

below.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

45W

0 (4-wire)

Touchpanel Type Selection

0: 4-wire

1: 5-wire

0:5

RPU

000001

(64k

Ω)

Internal Pull-up resistor for Pen Detection

000000: RESERVED (do not use this setting)

000001: RPU/1 = TYP 64k

Ω (most sensitive)

000010: RPU /2 = TYP 32k

Ω

… (pull-up = RPU / binary value of RPU)

(Refer to page 9 for RPU specification)

78h

PIL

0 (200

µA)

Current used for pressure measurement

0: IP = 200

µA

1: IP = 400

µA

Table 25 Touchpanel Digitiser Control (Physical Characteristics)

POWER MANAGEMENT

To save power, the touchpanel digitiser and the pen-down detector can be independently disabled

when they are not used. The power consumption of the pen-down detector is normally negligible,

except when the pen is down.

The state of the digitiser and pen down detector is controlled by the following bits.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

15:14

PRP

Pen ADC/AUX ADC enable

00 – Pen digitiser off, pen detect off, no

wake-up on pen down (default)

01 – Pen digitiser powered off, pen detect

enabled, touchpanel digitiser wakes up

(changes to state 11) on pen-down

10 – Pen digitiser off, pen detect enabled,

no wake-up on pen down

11 – Pen digitiser and pen detect enabled

78h

RPR

Wake-up on pen-down mode

0: Wake-up the AC-Link only (hold

SDATAIN high until controller sends warm

reset or cold reset)

1: Wake-up the WM9712L without waiting

for a reset signal from the controller

Table 26 Touchpanel Digitiser Control (Power Management)

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