16

3M™ MicroTouch™ Controller RX142 Reference Guide

3M Touch Systems, Inc. Proprietary Information

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 operating mode for the RX142 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.

Mode Stream 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,

provided that the interrupts are sent as recommended, your software always knows

exactly 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 responses.

The commands listed in the following table are those that 3M Touch Systems currently

uses for development and recommends that you use only these commands.

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.

Sending Commands to the Controller

When you send a command to the controller, you must use the correct command format.

The general format of a command is as follows:

<Header>Command<Terminator>

Note:

The following descriptions of header, command, and terminator, use 3M Touch

Systems terminal emulator key sequences. You may need to enter the sequence in a

different format, depending on your emulator.

The header is the first character in the command string and is the ASCII start-of-header

control character SOH. The hexadecimal code for the ASCII SOH control character is 01.

To start the command sequence, use the key combination: Ctrl A (^A). If you are

working with an IBM PC compatible system, the Ctrl A key combination immediately

returns an ASCII ☺ character.

The command, which always follows the header, consists of ASCII uppercase letters and

numbers only (printable characters).