sx8652 Semtech Corporation, sx8652 Datasheet - Page 26

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

Figure 23 shows the SPI working in automatic mode with CONDIRQ=1. After the first sentence send through the SPI to
make the initialization, traffic is reduced as only reads are required.
The processing time is the
necessary time for the SX8652 to
makes the pendetection, the
settling time (POWDLY) and the
conversion. This time increases
with the number of channel
selected and the filter used.All
succeeding conversions notifies
the host by an interrupt signal and
the host only needs to issue the
SPI read command.
The reads occur at the RATE
interval.
7.3. PENDET Mode
Figure 24. PENDET Mode Flowchart
7.4. PENTRIG Mode
The PENTRIG mode offers the best 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 signalled only when the screen is touched and coordinates are available.
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 flowchart and the SPI working is illustrated in Figure 25.
Revision V1.6/July 2010
©2010 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
RegStat read
Touch Detected ?
Release Interrupt
PENDET MODE
Set interrupt
yes
NIRQ=0
NIRQ=1
no
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.
TOUCH
CS
DIN
NIRQ
DOUT
Figure 23.
Read Channel Data CMD
Data from SX8652
SPI working in AUTO mode
15kV ESD Low Power 4-Wire / 5-Wire Resistive
Page 26
Touchscreen Controller with SPI Interface
Time is 1/ RATE
Processing time
www.semtech.com
DATASHEET
SX8652