3M M2256PW User Manual - Page 30

30 3M™ Display M2256PW User Guide 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 Multitouch is the default format for the 3M™ PX serial controller. In Format Tablet Multitouch, the controller sends 6 bytes per point and provides the most rapid response time to a touch. Refer to the Format Tablet Multitouch 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 PX serial 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 Table 17 are those that 3M Touch Systems currently uses for development. 3M Touch Systems recommends that you use only these commands for 3M™ PX serial 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. 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: Command 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. 3M Touch Systems, Inc. Proprietary Information