ALPS Touchpad Protocol
Introduction
Currently the ALPS touchpad driver supports two protocol versions in use by
ALPS touchpads, the “old” and “new” protocol versions. Fundamentally these
differ only in the format of their event packets (in reality many features may
be found on new protocol devices that aren’t found on the old protocol
devices, but these are handled transparently as feature differences rather
than protocol differences).
Detection
All ALPS touchpads should respond to the “E6 report” command sequence:
E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or
00-00-64 if no buttons are pressed. The bits 0-2 of the first byte will be 1s
if some buttons are pressed.
If the E6 report is successful, the touchpad model is identified using the “E7
report” sequence: E8-E7-E7-E7-E9. The response is the model signature and is
matched against known models in the alps_model_data_array.
Packet Format
In the following tables, the following notation us used.
CAPITALS = stick, miniscules = touchpad
?’s can have different meanings on different models, such as wheel rotation,
extra buttons, stick buttons on a dualpoint, etc.
PS/2 packet format
byte 0: 0 0 YSGN XSGN 1 M R L
byte 1: X7 X6 X5 X4 X3 X2 X1 X0
byte 2: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0
Note that the device never signals overflow condition.
ALPS Absolute Mode - Old Format
byte 0: 1 0 0 0 1 x9 x8 x7
byte 1: 0 x6 x5 x4 x3 x2 x1 x0
byte 2: 0 ? ? l r ? fin ges
byte 3: 0 ? ? ? ? y9 y8 y7
byte 4: 0 y6 y5 y4 y3 y2 y1 y0
byte 5: 0 z6 z5 z4 z3 z2 z1 z0
ALPS Absolute Mode - New Format
byte 0: 1 ? ? ? 1 ? ? ?
byte 1: 0 x6 x5 x4 x3 x2 x1 x0
byte 2: 0 x10 x9 x8 x7 ? fin ges
byte 3: 0 y9 y8 y7 1 M R L
byte 4: 0 y6 y5 y4 y3 y2 y1 y0
byte 5: 0 z6 z5 z4 z3 z2 z1 z0
Dualpoint device – interleaved packet format
byte 0: 1 1 0 0 1 1 1 1
byte 1: 0 x6 x5 x4 x3 x2 x1 x0
byte 2: 0 x10 x9 x8 x7 0 fin ges
byte 3: 0 0 YSGN XSGN 1 1 1 1
byte 4: X7 X6 X5 X4 X3 X2 X1 X0
byte 5: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0
byte 6: 0 y9 y8 y7 1 m r l
byte 7: 0 y6 y5 y4 y3 y2 y1 y0
byte 8: 0 z6 z5 z4 z3 z2 z1 z0
