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Simultaneous Support for Two Pointing Devices

IP.com Disclosure Number: IPCOM000107585D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 3 page(s) / 107K

Publishing Venue

IBM

Related People

Flowers, DR: AUTHOR [+3]

Abstract

A method is described by which two devices that use a PS/2* Auxiliary Pointing Device (APD) interface can "share" the same physical port on the PS/2. The method is applicable to any type of pointing device. However, one of the devices, the primary device, must have a controller which multiplexes the signals from the secondary device onto a single connection to the PS/2. The primary device will be connected directly to the PS/2 APD port. A sample system is described in which a touch screen monitor is attached to the APD port and a standard mouse is connected to the touch screen monitor.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Simultaneous Support for Two Pointing Devices

       A method is described by which two devices that use a
PS/2* Auxiliary Pointing Device (APD) interface can "share" the same
physical port on the PS/2.  The method is applicable to any type of
pointing device.  However, one of the devices, the primary device,
must have a controller which multiplexes the signals from the
secondary device onto a single connection to the PS/2.  The primary
device will be connected directly to the PS/2 APD port.  A sample
system is described in which a touch screen monitor is attached to
the APD port and a standard mouse is connected to the touch screen
monitor.

      Three distinct approaches are described:
1.   SOFTWARE SWITCHABLE USAGE OF THE POINTING DEVICES
      In this example, only a single pointing device is active at a
given time.  A software switch in the touch screen controller (TSC)
routes all of the data between one source (either the mouse or the
touch screen) and the PS/2.  This switch will be controlled by
software commands sent by the PS/2.
      1.   Device to PS/2 Communications.
           Only the data from the active device is sent to the PS/2.
In mouse mode, the unaltered mouse data will be sent to the PS/2.  In
a touch screen mode, the mouse will be disabled by the TSC and only
touch screen data will be sent to the PS/2.
      2.   PS/2 to Device Communications.
           The data sent by the PS/2 is received only by the active
device.  No header or command bytes are needed since the destination
is implicitly defined to be the active device.  In mouse mode each
command is decoded by the TSC.  If it is a "switch active device"
command, the active device will be disabled and subsequent data will
be routed to the newly active device.  Otherwise, the number of
additional data bytes will be calculated.  Knowing this will prevent
mistaking a data byte with a command byte.
      The advantage of this approach is compatibility with existing
mouse programs.  Batch files or applications could be written so that
the active device could be changed on an application by application
basis.
2.   CONCURRENT USAGE OF THE POINTING DEVICES.
      This approach allows both devices to be active at the same
time.  A software multiplexer and a data formatter combine the two
data streams.
      1.   Device to PS/2 Communications.
           Data is received from the touch screen function and from
the mouse.  The data from the mouse is re-formatted (...