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SC400 Controller Communications
Format Tablet
Syntax:
<SOH>FT<CR>
Response:
<SOH>0<CR>
The controller will respond with ACK for compatibility with older controllers. This
format is the only format supported by this controller.
With the controller in Format Tablet mode, touching the screen causes the controller to
return a response in the following format:
SXxYy
S
= Status byte, first byte of data. Refer to Table 4.
Xx = X (horizontal) coordinate data; second and third bytes of data.
Yy = Y (vertical) coordinate data; fourth and fifth bytes of data.
Description:
Outputs the X/Y touch coordinate data in a 5-byte packet. The packet includes 1 status
byte and 4 bytes of binary X/Y coordinate data. The protocol also establishes the X and Y
coordinate output as 14 binary bits providing a range of 0 to 16,383.
The low order bits (X3 – X0 and Y3 – Y0) are not significant in a 1024 by 1024 touch
screen because data can fluctuate with each touch, and therefore may not be completely
accurate.
Table 4 Data Sequence
Data Sequence
S
X
X
Y
Y
Table 5 defines the status bits (Byte 1) for the Format Tablet data.
Table 5 Format Tablet Status Bits
Bit
Description
S0 – S5 Reserved
S6
Proximity (touch state)
S7
Packet synchronization Always 1.
Positive response.
7
6
Byte 1
1
S6
Byte 2
0
X6
Byte 3
0
X13 X12
Byte 4
0
Y6
Byte 5
0
Y13 Y12
Values
—
1 = Touch screen is being touched (a touchdown or a continued touch).
0 = Touch screen is not being touched (a touch liftoff or inactive).
When the proximity bit changes from 1 to 0 (touch liftoff), the controller
outputs one final set of X/Y coordinate data with the bit equal to 0 and the
X/Y coordinate data equal to the last touch point.
3M Touch Systems Proprietary Information
Bits
5
4
3
2
S5
S4
S3
S2
X5
X4
X3
X2
X11
X10
X9
Y5
Y4
Y3
Y2
Y11
Y10
Y9
21
1
0
S1
S0
X1
X0
X8
X7
Y1
Y0
Y8
Y7
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