WM8948ECSSLASHR datasheet(94/189 Pages) WOLFSON

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WM8948

Production Data

PD, May 2011, Rev 4.1

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

TCH_Y_ENA

Enables Y-axis touch panel

measurements

0 = Disabled

1 = Enabled

TCH_X_ENA

Enables X-axis touch panel

measurements

0 = Disabled

1 = Enabled

7:5

TCH_DELAY

[2:0]

000

Settling time between X, Y and Z

measurements. (Nominal timing

only; typically +/-20% of quoted

values.)

000 = 30us

001 = 60us

010 = 120us

011 = 240us

100 = 480us

101 = 960us

110 = 1920us

111 = 3840us

4:0

TCH_RATE [4:0]

0_0000

Touch Panel Rate

0_0000 = Manual conversion

0_0001 = 16kHz

0_0010 = 32kHz

…(16kHz steps)

1_1111 = 496kHz

R56 (38h)

Touch Control

TCH_PDONLY

Select Automatic conversions only

when Pen Down is detected. (No

effect on Manual conversion.)

0 = Normal

1 = Pen-Down only

TCH_ISEL

Pressure measurement current

select

0 = 230uA

1 = 460uA

3:0

TCH_RPU [3:0]

0111

Pen-Down sensitivity (pull-up

resistor)

0000 = 64k (most sensitive)

0001 = 64k / 2

0010 = 64k / 3

0011 = 64k / 4

….

1111 = 64k / 16 (least sensitive)

Table 60 Touch Panel Control

TOUCH PANEL READBACK

Measured data from the Touch Panel controller is read via the Touch Data registers. The X-axis, Y-

axis and Z-axis (pressure) measurements are provided in the TCH_X, TCH_Y and TCH_Z registers

respectively. The TCH_PD1, TCH_PD2 and TCH_PD3 bits indicate whether the Pen Down status

was asserted when the measurement set was made.

To read a set of Touch Panel measurements, the host processor must access each of the applicable

Touch Data registers. When the host processor starts to read these registers, the WM8948 will

inhibit any new touch panel measurements until the host processor has read all of the applicable

registers. This ensures that the data read by the host processor all relates to the same set of

measurements.

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