WM9705 datasheet(45/55 Pages) WOLFSON

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WM9705

Production Data

PD Rev 4.0 December 2003

Figure 22 Control of ADC Conversions : Polled Co-ordinate Method

Note:

The pressure measurement is the difference between the voltage values measured between the resistive plates in the screen.

As two values have to be obtained before the calculation can take place, two data acquisition cycles are required as illustrated

above.

Screen Switch

/ ADC mux

mode

Different types of polled conversion with delay set to 0 (1 frame)

POLL

SYNC

ADR=1

DELAY

CONVERT

ADC MODE

Write to 0x76

with 0xB800

SDOUT

PENDATA

Poll = 1, Coord = 0, ADR = 001 ( 0x76 = 0x9000 ) = X Measurement

DELAY

CONVERT

ADR=2

DELAY

CONVERT

ADR=3(1)1

DELAY

CONVERT

ADR=3(2)1

X Measurement

Y Measurement

Pressure

Measurement

POLL

ADR=1

DELAY

CONVERT

ADC MODE

Write to 0x76

with 0x9000

PENDATA

X Measurement

Coord = 1, ADR = 011 ( 0x76 = 0xB800 ) = X, Y and Pressure

SDOUT

POLL

ADR=1

DELAY

CONVERT

ADC MODE

Write to 0x76

with 0xD800

SDOUT

PENDATA

DELAY

CONVERT

ADR=2

DELAY

CONVERT

ADR=5

X Measurement

AUX Measurement

Coord = 1, ADR = 101 ( 0x76 = 0xD800 ) = X, Y and AUX

Y Measurement

Screen Switch

/ ADC mux

mode

Screen Switch

/ ADC mux

mode

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