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3M™ Multi-touch Display M2256PW User Guide 21
3M Touch Systems, Inc. Proprietary Information – 37531 Rev D
APPENDIX A
3M™ PX USB Controller Communications
This appendix is intended for software developers only and discusses the fundamentals
of communicating with the PX controller. The firmware commands, which are usually
issued by a driver or utility program on the host system, control the operation of the
controller. This appendix lists the recommended firmware commands and describes how
to use each of these commands.
Overview of USB Firmware Communications
Developers may use this information when writing touch applications, developing
custom drivers or touch configurations, or testing their touch systems. Developers can
issue commands to initialize the controller, select operating modes, and execute
diagnostic functions.
Note: This document assumes you are familiar with USB standards and modes of
communication with USB devices, as well as firmware commands and how to use them.
Executing some commands may alter the performance of your sensor and render it
inoperable. You should be aware of the results before executing any firmware
commands.
To optimize the performance of the PX controller and simplify the development of
custom drivers, 3M Touch Systems recommends you use the commands listed in this
appendix for current development.
Communication Basics
This section provides information on sending firmware commands to the controller and
interpreting the responses that the controller returns. The default operation of the PX
controller is USB Rev 2.0 full speed.
The USB command set is implemented by using vendor requests and vendor reports, i.e.,
vendor specific transactions. The controller issues some reports without prompting the
computer. The computer can also send requests to the controller to change how it
operates or receives information about the controller. The controller issues a