WM8311 datasheet(132/302 Pages) WOLFSON

132 / 302 page

WM8311

Pre-Production

PP, May 2012, Rev 3.1

132

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

TCH_PDONLY

Select Automatic conversions only

when Pen Down is detected. (No

effect on Manual conversion.)

0 = Normal

1 = Pen-Down only

Table 71 Touch Panel Control

19.4 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. (Note that Z-axis measurement is applicable to 4-wire mode only.) When the

host processor starts to read these registers, the WM8311 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.

The touch panel inhibit (preventing new touch panel measurements) commences when any of the

Touch Data registers is read. The touch panel inhibit ceases when all selected Touch Data registers

have been read, or if a read/write operation is made to any other register.

If all 3 touch panel channels are selected (using TCH_X_ENA, TCH_Y_ENA and TCH_Z_ENA as

described in Section 19.3), then all 3 Touch Data registers must be read before further measurements

are permitted. If fewer channels are selected, then only those selected channels need to be read

before touch panel measurements are enabled again.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R16426 (402Ah)

Touch Data X

TCH_PD1

Pen down status (indicates if the

Pen Down was detected prior to

the TP measurement)

0 = Pen Down not detected

1 = Pen Down detected

11:0

TCH_X [11:0]

000h

Touch panel X-axis data

R16427 (402Bh)

Touch Data Y

TCH_PD2

Pen down status (indicates if the

Pen Down was detected prior to

the TP measurement)

0 = Pen Down not detected

1 = Pen Down detected

11:0

TCH_Y [11:0]

000h

Touch panel Y-axis data

R16428 (402Ch)

Touch Data Z

TCH_PD3

Pen down status (indicates if the

Pen Down was detected prior to

the TP measurement)

0 = Pen Down not detected

1 = Pen Down detected

11:0

TCH_Z [11:0]

000h

Touch panel Z-axis data

Table 72 Touch Panel Readback

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