Abstract
A new multitouch sensing strategy, named the Touch Prediction
and Window Sensing (TPWS), is proposed and realized in this paper
for projected capacitive touch screens. The detection procedures of
TPWS are divided into two stages: a pre-sensing stage for predicting
the possible touched regions, and a window sensing stage for obtaining
the accurate touched positions. Since the measurements of the untouched
sensing cells are reduced significantly, the TPWS strategy needs lower
efforts on signal readout and data processing than the traditional
strategies. A prototype system was designed and realized, which consists
of three identical 48-channel readout chips, a 15-in capacitive touch
screen, and a commercial host processor. The readout chip is specially
designed for the TPWS strategy using
${0.13}~\mu{m}$
1.8 V/5 V
CMOS process. The measurement results show that, the total power consumption
of the system is only about 65 mW with a power supply of 5 V,
and the reporting rate of the system achieves 500 Hz for no touches
and 83 Hz for ten touches. The area of the readout chip is only
0.087
$ ~{mm}^{2}$
per sensing channel. The proposed TPWS strategy can be
used to realize low-power and low-cost multitouch screen system, and
it is especially efficient for large-sized screen.
© 2016 IEEE
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