SX8650 Datasheet, PDF (43/56 Pages) Semtech Corporation – World’s Lowest Power & Smallest Footprint 4-wire Resistive Touchscreen Controller with 15kV ESD

SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
I2C
init setup
NIRQ
bias channel
X
POWDLY
sample channel
convert channel
Y
POWDLY
read x, y
position
SETDLY SETDLY
SETDLY SETDLY
Figure 38. auto mode, sequential 2-channel conversion, 3 sample filtering and interrupt signaling, first
conversion
Figure 38 shows the very first conversion of 2 channels. Figure 39 shows the subsequent conversions.
I2CRegCtrl0=0xB8 //1 kCPS RATE, 140us POWDLY
I2CRegCtrl1=0x21 // Interrupt enable, three samples filtering
I2CRegChanMsk=0xC0
I2C
read x, y
position
NIRQ
bias channel
x
y
RATE
x
sample channel
convert channel
Figure 39. auto mode, sequential 2-channel conversion, 3 sample filtering and interrupt signaling, subsequent
conversions
All succeeding conversions notifies the host by an interrupt signal and the host only needs to issue the I2C read command.
The reads occur at the RATE interval.
5.3. 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 I2CRegStat.
5.4. PENTRIG Mode
The PENTRIG mode offers the best compromise between power consumption and coordinate throughput.
In this mode the SX8650 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.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 42
www.semtech.com