SX8652ICSTRT Semtech, SX8652ICSTRT Datasheet - Page 24

• Manufacturer Part Number: SX8652ICSTRT
• Description: 4/5-wire Resistive Touch Screen Controller (SPI)
• Manufacturer: Semtech

10. Application Information
This section describes in more detail application oriented data.
10.1. Acquisition Setup
Prior to an acquisition, the SX8652 can be setup by writing the control registers. Registers are written by issuing the
register write command. They can be read by issuing the read command. Please refer to the section [9.7].
10.2. Channel Selection
The SX8652 can be setup to start a single channel conversion or to convert several channels in sequence. For a single
conversion, the channel to be converted is determined from the CHAN(2:0) field in the command word (defined in
Table 12).
Several channels defined in RegChanMsk can be acquired sequentially by setting the CHAN(2:0) field to SEQ. The
channels will be sampled in the order X, Y, Z1, Z2, AUX.
10.3. Noise Reduction
A noisy environment can decrease the performance of the controller. For example, an LCD display located just under the
touch screen can adds a lot of noise on the high impedance A/D converter inputs.
10.3.1. POWDLY
In order to perform correct coordinates acquisition properly, some time must be given for the touch screen to reach a
proper level. It is a function of the PCB trace resistance connecting the SX8652 to the touchscreen and also the
Revision V1.7/October 2010
©2010 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
RegSoftReset
RegChanMsk
RegStat
Register
Host writing to this register is ignored.
Bit Default
4:0
7:0
7
6
5
4
3
0
0
0
7
6
5
00000
0x00
1
1
0
0
0
0
0
0
0
0
1
XCONV
YCONV
Z1CONV
Z2CONV
AUXCONV
reserved
reserved
reserved
CONVIRQ
PENIRQ
RSTEVENT A reset event has occurred
reserved
Writing 0xDE to this register reset the SX8652
Any other data will not affect the SX8652
Table 15. SX8652 Register
0: no sample
0: no sample
0: no sample
0: no sample
0: no sample
0: no IRQ pending
1: Conversion sequence finished
IRQ is cleared by the channel data read command
Operational in pen detect mode
0: no IRQ pending
1: Pen detected IRQ pending
IRQ is cleared by the RegStat reading
15kV ESD Low Power 4-Wire / 5-Wire Resistive
Page 24
Touchscreen Controller with SPI Interface
Description
1: Sample X channel
1: Sample Y channel
1: Sample Z1 channel
1: Sample Z2 channel
1: Sample AUX channel
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DATASHEET
SX8652