WM9713LGEFLSLASHV datasheet(62/108 Pages) WOLFSON

62 / 108 page

WM9713L

Pre-Production

PP Rev 3.0 June 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 78h, as shown

below.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

45W

0 (4-wire)

Touchpanel Type Selection

0: 4-wire

1: 5-wire

PIL

0 (200

µA)

Current used for pressure measurement

0: IP = 200

µA

1: IP = 400

µA

78h

0:5

RPU

000001

(64k

Ω)

Internal Pull-up resistor for Pen Detection

111111: 64k

Ω/63 = 1.02kΩ (least sensitive)

111110: 64K

Ω/62 = 1.03KΩ

… (pull-up = 64k

Ω / binary value of RPU)

000010: 64K

Ω/2 = 32KΩ

000001: 64k

Ω/1 = 64kΩ (most sensitive)

000000: RESERVED (do not use this setting)

Table 46 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 pen ADC is powered-down using PADCPD, register 3Ch bit 15.

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

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

3Ch

PADCPD

1 = off

Pen ADC power down

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 WM9713L without waiting

for a reset signal from the controller

Table 47 Touchpanel Digitiser Control (Power Management)

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