wm9705seft-v Wolfson Microelectronics plc, wm9705seft-v Datasheet - Page 45

• Manufacturer Part Number: wm9705seft-v
• Description: Multimedia Ac?97 Codec With Integrated Touch Screen Controller
• Manufacturer: Wolfson Microelectronics plc

WM9705
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.
w
Screen Switch
Screen Switch
Screen Switch
/ ADC mux
ADC MODE
/ ADC mux
ADC MODE
ADC MODE
/ ADC mux
PENDATA
PENDATA
PENDATA
mode
mode
Coord = 1, ADR = 011 ( 0x76 = 0xB800 ) = X, Y and Pressure
mode
Poll = 1, Coord = 0, ADR = 001 ( 0x76 = 0x9000 ) = X Measurement
SDOUT
SDOUT
SDOUT
Coord = 1, ADR = 101 ( 0x76 = 0xD800 ) = X, Y and AUX
SYNC
POLL
POLL
POLL
Write to 0x76
Write to 0x76
Write to 0x76
with 0xB800
with 0xD800
with 0x9000
X
X
X
DELAY
DELAY
DELAY
Different types of polled conversion with delay set to 0 (1 frame)
ADR=1
ADR=1
ADR=1
CONVERT
CONVERT
CONVERT
DELAY
DELAY
X Measurement
X Measurement
ADR=2
ADR=2
CONVERT
CONVERT
DELAY
DELAY
Y Measurement
ADR=3(1)
ADR=5
CONVERT
CONVERT
X Measurement
1
Y Measurement
DELAY
ADR=3(2)
PD Rev 4.5 July 2008
AUX Measurement
CONVERT
1
Production Data
Measurement
Pressure
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