SX8652ICSTRT Semtech, SX8652ICSTRT Datasheet - Page 17

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

The processing time is the
necessary time for the SX8652 to
makes the pen detection, the
settling time (POWDLY) and the
conversion of the selected
channels. This time increases with
the number of channel selected
and the filter used. NIRQ interrupt
signal notifies the host when the
conversions are done.
The host just need to read the
channels data to release the
interrupt.
8.3. PENDET Mode
The PENDET mode can be used if the host only needs to know if the screen has been touched or not and take from that
information further actions. When pen detect circuitry is triggered the interrupt signal NIRQ will be generated and the status
register bit ‘PENIRQ’ will be set. The bit is cleared by reading the status register RegStat. The PENDET working is
illustrated in Figure 16.
8.4. PENTRIG Mode
The
compromise between power consumption
and coordinate throughput.
In this mode the SX8652 will wait until a pen
is detected on the screen and then starts the
coordinate conversions. The host will be
signaled only when the screen is touched and
coordinates are available. The flowchart is
describes in Figure 16.
The coordinate rate in pen trigger mode is
determined by the speed of the host reading
the channels and the conversion times of the
channels. The host performs the minimum
number of SPI commands in this mode.
The host has to wait for the NIRQ interrupt to
make the acquisition of the data.
The SPI working is illustrated in Figure 15.
Revision V1.7/October 2010
©2010 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
PENTRIG
mode
offers
the
TOUCH
CS
DIN
NIRQ
DOUT
best
Read Channel Data CMD
Data from SX8652
TOUCH
NIRQ
CS
DIN
DOUT
Read Channel Data CMD
15kV ESD Low Power 4-Wire / 5-Wire Resistive
Data from SX8652
Page 17
Touchscreen Controller with SPI Interface
Conversion time
Figure 15. SPI working in PENTRIG mode
Figure 14. SPI working in AUTO mode
Time is 1/ RATE
Processing time
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SX8652