WM9712L datasheet(44/77 Pages) WOLFSON

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WM9712L

Production Data

PD Rev 4.5 August 2006

When COO is ‘0’, the WM9712L performs one type of measurement once (in polling mode) or

continuously (in continuous mode).

The co-ordinate mode (COO = ‘1’) makes it easier to obtain co-ordinate pairs rather than single co-

ordinates. In polling-coordinate mode (CTC = ‘0’, COO = ‘1’), the WM9712L performs an X

measurement, followed by a Y measurement, followed by an additional measurement determined by

ADCSEL, then stops. In continuous-coordinate mode (CTC = ‘1’, COO = ‘1’), the WM9712L

continuously repeats a sequence consisting of an X-co-ordinate measurement, followed by a Y co-

ordinate measurement, followed by an additional measurement determined by ADCSEL (if ADCSEL

= 000, the sequence is XYXYXY… only).

DATA READBACK

The output data word of the touchpanel interface consists of three parts:

•

Pen Status (1 bit) – this is also passed to the GPIO logic block, which can be

programmed to generate an interrupt and/or wake up the WM9712L on pen down (see

GPIO and Interrupt Control).

•

Output data from the touchpanel ADC (12 bits)

•

ADCSRC: 3 additional bits that indicate the source of the ADC data. With COO = ‘0’,

ADCSRC echoes ADCSEL. However, in co-ordinate mode (COO = ‘1’), the WM9712L

schedules different types of measurements autonomously and sets the ADCSRC bits

accordingly (see “Measurement Types”).

This data is stored in register 7Ah, and can be retrieved by reading the register in the usual manner

(see AC-Link Interface section). Additionally, the data can also be passed to the controller on one of

the AC-Link time slots not used for audio functions.

If the data is being read back using the polling method, there are several ways to determine when a

measurement has finished:

•

Reading back the POLL bit. If it has been reset to ‘0’, then the measurement has finished.

•

By monitoring the ADA signal, see GPIO and interrupt section

•

Reading back 7Ah until the new data appears

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

PNDN

Pen status (read-only)

0: Pen Up

1: Pen Down

14:12

ADCSRC

000

Touchpanel ADC Source

000: No measurement

001: X co-ordinate measurement

010: Y co-ordinate measurement

011: Pressure measurement

(4-wire touchpanels only)

100: COMP1/AUX1 measurement (pin 29)

101: COMP2/AUX2 measurement (pin 30)

110: BMON/AUX3 measurement (pin 31)

111: WIPER/AUX4 measurement (pin 12)

7Ah

AC-Link slot

selected by

SLT

11:0

ADCD

000h

Touchpanel ADC Data (read-only)

Bit 11 = MSB

Bit 0 = LSB

78h

WAIT

0: No effect (new ADC data overwrites

unread data in register 7Ah)

1: New data is held back, and

measurements delayed, until register 7Ah is

read)

Table 29 Touchpanel Digitiser Data

To avoid losing data that has not yet been read, the WM9712L can delay overwriting register 7Ah

with new data until the old data has been read. This function is enabled using the WAIT bit.

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