24 EX II Serial Controllers Reference Guide
3M Touch Systems Proprietary Information
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.
Table 4 Data Sequence
MSB* Bits LSB*
Data Sequence 7 6 5 4 3 2 1 0
S- Byte 1 1 S6 Reserved
X- Byte 2 0 X3 X2 X1 X0 Reserved
x- Byte 3 0 Xs** X9 X8 X7 X6 X5 X4
Y- Byte 4 0 Y3 Y2 Y1 Y0 Reserved
y- Byte 5 0 Ys** Y9 Y8 Y7 Y6 Y5 Y4
*MSB = Most Significant Bit, LSB = Least Significant Bit
** s = sign bit
Table 5 describes the meaning of the bits in the status byte (Byte 1).
Table 5 Calibrate Raw Status Bits
Bit Description Values
S0 – S5 Reserved —
S6 Proximity (touch state) 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.
S7 Packet synchronization Always 1.
Diagnostic Command
Syntax: <SOH>DX<CR>
Description: This command requests the controller to check for touch screen failures such as broken
corners, broken wires, etc.
Response: <SOH>0<CR> Positive response.
<SOH>1<CR> Command not supported.
<SOH>2<CR> Failure detected.
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