40 3M™ Multi-Touch Chassis Display User Guide
3M Touch Systems, Inc. Proprietary Information – TSD-39373B
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 Multi-Touch is the default format for the
3M™ PX serial controller. In Format Tablet Multi-Touch, the controller sends 6 bytes
per point and provides the most rapid response time to a touch.
Note that 3M MicroTouch Software automatically sets communications parameters to
N81.
The format is a six byte packet that includes one status byte, four bytes of binary X,Y
position data and a touch ID. The X,Y coordinates are 14 bits, providing a range of 0 to
16,383. The data is sent in the following format:
Table 17. Touch Data Format Settings
Data Sequence Bits
7 6 5 4 3 2 1 0
Status - Byte 1 1 P
1
0 0 0 0 0
0
X - Byte 2 0 X6 X5 X4 X3 X2 X1 X0
X - Byte 3 0 X13 X12 X11 X10 X9 X8 X7
Y - Byte 4 0 Y6 Y5 Y4 Y3 Y2 Y1 Y0
Y - Byte 5 0 Y13 Y12 Y11 Y10 Y9 Y8 Y7
ID – Byte 6 0 N6 N5 N4 N3 N2 N1 N0
Note 1: P is the proximity bit. It is set to 1 when there is a touch, 0 for a liftoff.
The ID is associated with a touch stream from one finger. The ID, in the range of 0-127,
is assigned on a rotating basis at touchdown. A finger touch stream consists of a
touchdown, maybe some continuing touch points, ending with a liftoff. The ID is
released on liftoff, and becomes available to be reassigned.
When multiple fingers are down, the packets from the touch streams are sent interleaved.
There is no order imposed on the interleave.
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 3M™ 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.
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