Specifications

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Of prime consideration to the
applications programmer is the interaction or
communication between system hardware
units, the system software packages, and the
vital interface between the touch application
and the user.
Hardware Interface Options
Touch systems are designed to interface
with the host in a variety of different
configurations.
One configuration involves communi-
cating with the host system through a serial
port. Examples include the RS-232 and RS-
422 protocols.
Another configuration involves parallel
communication via a bus standard.
Examples include ISA/EISA, microchannel,
and PC/104
TM
.
Another interface method uses the
mouse port. In this method, the touch
system is connected to the host computer’s
mouse port and uses either a standard mouse
interface protocol or a proprietary touch
system interface protocol.
Another interface configuration
involves the use of daisy-chained input
devices, such as the Apple Desktop Bus
TM
.
Some vendors have chip sets available
that can be added to the host’s electronics
and packaging. The chip sets typically
contain all of the functions required to
control and communicate with the touch
system as well as the host’s electronics.
Touch vendors have proprietary
software interface protocols unique to their
touch systems. All of the touch vendors’
software protocols report an x and y
coordinate; some technologies permit the
reporting of a z coordinate as well.
Direct Interface Method
In the direct interface method, the touch
application communicates directly with the
touch system using the proprietary interface
protocol of the touch system.
Software Drivers
Software drivers are available from
touch vendors that assist the touch
application developer in interfacing to the
touch system. These drivers usually provide
calibration and scaling support, and
communicate with the touch system using
the touch vendor’s proprietary interface
protocol, and with the touch application via a
simple application program interface (API).
Section 7. Programming Considerations