14
3M™ MicroTouch™ Controller SX112 Reference Guide
3M Touch Systems, Inc. Proprietary Information
Controller Default Settings
Communication Parameters
The default operation of the SX112 controller is N81 (no parity, 8 data bits, and 1 stop
bits) at 9600 baud.
Data Format
Data format
refers to the type of packet the controller uses to send the X/Y touch
coordinates to the host system. Format Tablet is the default format for the 3M™
MicroTouch™ SX112 controller. In Format Tablet, the controller sends 5 bytes per point
and provides the most rapid response time to a touch.
•
Format Tablet is supported by all current 3M™ MicroTouch™ touch controllers.
•
It is the standard for current 3M Touch Systems product development and is the
format used by all touch drivers written by 3M Touch Systems.
Refer to the Format Tablet command in the firmware reference section. Note that 3M
MicroTouch Software automatically sets communications parameters to N81.
Operating Mode
The
operating mode
specifies the conditions under which the controller sends the X/Y
touch coordinates (input data packet) to the host system.
Mode Stream is the default operating mode for the SX112 controller. In Mode Stream,
the controller sends a continuous stream of data packets when the sensor is touched. The
controller sends the data as long as a touch continues on the sensor.
Because Mode Stream sends touch data continually, it is the most versatile mode, and it
provides the best response time and overall feel.
3M Touch Systems recommends that the touch driver generate an interrupt as each packet
in the data stream arrives. Because touchdown and liftoff events are specially coded, your
software can generate mouse events that correspond to what the user is doing. This
enables instant feedback and prevents data loss.
Communicating with the Controller
This section provides information on sending firmware commands to the controller and
interpreting the responses that the controller returns.
The commands listed in the following table are those that 3M Touch Systems currently
uses for development. 3M Touch Systems recommends that you use only these
commands for 3M™ MicroTouch™ SX112 controller development.
Commands to the controller are sent on the signal
Receive Data
(RXD) line as a serial
data stream. For each command it receives, the controller sends a response to the host on
the signal
Transmit Data
(TXD) line also as a serial data stream.
