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EPSON
S1C88409 TECHNICAL MANUAL
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Touch Panel Controller)
Pen-down check
Write "1" to the PDC register to start pen-down
check.
When checking a pen-down after turning OSC3
off, the internal power supply circuit, OSCC and
stabilization waiting time must be controlled after
a pen-down is detected. To increase the response
time until the coordinate detection starts, the pen-
down should be checked when OSC3 is on or
using the RST register not the PDC register.
However, this method increases current consump-
tion.
Starting coordinate detection
Coordinate detection should be started using a
pen-down interrupt.
Write "1" to the PRAD and PRTP registers so that
the prescaler supplies the clocks to the A/D
converter and the touch panel controller.
Then write "1" to the RST register to start coordi-
nate detection.
Reading coordinate values
An interrupt occurs when coordinate values for a
point are written to the coordinate data registers
(DX, DY). Read coordinate data using the interrupt
and then execute the necessary processing.
Coordinate data varies according to the panel to be
used and operating environment. Therefore, first
get data of the panel origin point and used area to
make a correction value for converting the register
data into an actual coordinate. Drawing processing
should be done by correcting coordinate data
using the correction value.
Be sure to read all the coordinate data registers
(00FFA8, 00FFA9, 00FFAA, 00FFAB) after a data
update interrupt is generated. This process is
required if the coordinate data at that point is
unnecessary because the next data update inter-
rupt cannot be generated if all the register data are
not read.