sx8652 Semtech Corporation, sx8652 Datasheet - Page 17

• Manufacturer Part Number: sx8652
• Description: 15kv Esd Low Power 4-wire / 5-wire Resistive Touchscreen Controller With Spi Interface
• Manufacturer: Semtech Corporation

5.3. Pen Detection
The pendetect pull-up resistor and detector continue to monitor the X+/BR pin as in 4-wire mode. The wiper panel is
grounded at the AUX_WIPER pin to provide the grounding path for a screen touch event.
If a pressure is applied to the surface, a current path is created and will bias the touchscreen between BR and the wiper
probe.
6. Data Processing
Figure 19. Filter structure
.
6.1. Host Interface and Control
The host interface consists of SPI (DIN, DOUT, SCLK, NCS) and the NIRQ, NRST signals.
The SPI implemented on the SX8652 is set to the common setting CPOL=0 and CPHA=0.
It means data are sampled on the rising edge of the clock, and shifted on the falling one. The default state of the clock
when NCS gets asserted is low.
If a host send a command while the system is busy, the command is discarded.
The supported SPI access formats are described in the next sections:
Revision V1.6/July 2010
©2010 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
ADC
c
n
,c
n-1
,c
FILT
n-2
0
1
2
3
,...
Preprocessing
Sort: .>.>.>.>.
s
N
n
1
3
5
7
filt
s n
N
N
1
n
n
FILT
∑
No average.
3 ADC samples are averaged
5 ADC samples are averaged
c max1
=
7 ADC samples are sorted and the 3 center samples are averaged
N
i
=
=
s n
0
1
c
1
-- -
3
1
-- -
3
1
-- -
5
n
=
i
4079
----------- -
4095
4079
----------- -
4095
4079
----------- -
4095
c n
c max2
c n
c a
c n
s
n
+
+
+
c b
Table 7. Filter order
c n 1
c n 1
c a
–
+
–
c c
15kV ESD Low Power 4-Wire / 5-Wire Resistive
+
+
c b
Page 17
SPI
c n 2
c n 2
–
–
c c
Processing
Touchscreen Controller with SPI Interface
+
c min1
c n 3
–
The SX8652 offers 4 types of data processing
which allows the user to make trade-offs between
data throughput, power consumption and noise
rejection.
The parameter FILT is used to select the filter
order N
will be improved with a high order to the detriment
of the power consumption.
+
c n 4
c min2
–
filt
as seen in Table 7. The noise rejection
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