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1 ALPS Touchpad Protocol
2 ----------------------
4 Introduction
5 ------------
6 Currently the ALPS touchpad driver supports seven protocol versions in use by
7 ALPS touchpads, called versions 1, 2, 3, 4, 5, 6 and 7.
9 Since roughly mid-2010 several new ALPS touchpads have been released and
10 integrated into a variety of laptops and netbooks. These new touchpads
11 have enough behavior differences that the alps_model_data definition
12 table, describing the properties of the different versions, is no longer
13 adequate. The design choices were to re-define the alps_model_data
14 table, with the risk of regression testing existing devices, or isolate
15 the new devices outside of the alps_model_data table. The latter design
16 choice was made. The new touchpad signatures are named: "Rushmore",
17 "Pinnacle", and "Dolphin", which you will see in the alps.c code.
18 For the purposes of this document, this group of ALPS touchpads will
19 generically be called "new ALPS touchpads".
21 We experimented with probing the ACPI interface _HID (Hardware ID)/_CID
22 (Compatibility ID) definition as a way to uniquely identify the
23 different ALPS variants but there did not appear to be a 1:1 mapping.
24 In fact, it appeared to be an m:n mapping between the _HID and actual
25 hardware type.
27 Detection
28 ---------
30 All ALPS touchpads should respond to the "E6 report" command sequence:
31 E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or
32 00-00-64 if no buttons are pressed. The bits 0-2 of the first byte will be 1s
33 if some buttons are pressed.
35 If the E6 report is successful, the touchpad model is identified using the "E7
36 report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is
37 matched against known models in the alps_model_data_array.
39 For older touchpads supporting protocol versions 3 and 4, the E7 report
40 model signature is always 73-02-64. To differentiate between these
41 versions, the response from the "Enter Command Mode" sequence must be
42 inspected as described below.
44 The new ALPS touchpads have an E7 signature of 73-03-50 or 73-03-0A but
45 seem to be better differentiated by the EC Command Mode response.
47 Command Mode
48 ------------
50 Protocol versions 3 and 4 have a command mode that is used to read and write
51 one-byte device registers in a 16-bit address space. The command sequence
52 EC-EC-EC-E9 places the device in command mode, and the device will respond
53 with 88-07 followed by a third byte. This third byte can be used to determine
54 whether the devices uses the version 3 or 4 protocol.
56 To exit command mode, PSMOUSE_CMD_SETSTREAM (EA) is sent to the touchpad.
58 While in command mode, register addresses can be set by first sending a
59 specific command, either EC for v3 devices or F5 for v4 devices. Then the
60 address is sent one nibble at a time, where each nibble is encoded as a
61 command with optional data. This encoding differs slightly between the v3 and
62 v4 protocols.
64 Once an address has been set, the addressed register can be read by sending
65 PSMOUSE_CMD_GETINFO (E9). The first two bytes of the response contains the
66 address of the register being read, and the third contains the value of the
67 register. Registers are written by writing the value one nibble at a time
68 using the same encoding used for addresses.
70 For the new ALPS touchpads, the EC command is used to enter command
71 mode. The response in the new ALPS touchpads is significantly different,
72 and more important in determining the behavior. This code has been
73 separated from the original alps_model_data table and put in the
74 alps_identify function. For example, there seem to be two hardware init
75 sequences for the "Dolphin" touchpads as determined by the second byte
76 of the EC response.
78 Packet Format
79 -------------
81 In the following tables, the following notation is used.
83 CAPITALS = stick, miniscules = touchpad
85 ?'s can have different meanings on different models, such as wheel rotation,
86 extra buttons, stick buttons on a dualpoint, etc.
88 PS/2 packet format
89 ------------------
91 byte 0: 0 0 YSGN XSGN 1 M R L
92 byte 1: X7 X6 X5 X4 X3 X2 X1 X0
93 byte 2: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0
95 Note that the device never signals overflow condition.
97 For protocol version 2 devices when the trackpoint is used, and no fingers
98 are on the touchpad, the M R L bits signal the combined status of both the
99 pointingstick and touchpad buttons.
101 ALPS Absolute Mode - Protocol Version 1
102 --------------------------------------
104 byte 0: 1 0 0 0 1 x9 x8 x7
105 byte 1: 0 x6 x5 x4 x3 x2 x1 x0
106 byte 2: 0 ? ? l r ? fin ges
107 byte 3: 0 ? ? ? ? y9 y8 y7
108 byte 4: 0 y6 y5 y4 y3 y2 y1 y0
109 byte 5: 0 z6 z5 z4 z3 z2 z1 z0
111 ALPS Absolute Mode - Protocol Version 2
112 ---------------------------------------
114 byte 0: 1 ? ? ? 1 PSM PSR PSL
115 byte 1: 0 x6 x5 x4 x3 x2 x1 x0
116 byte 2: 0 x10 x9 x8 x7 ? fin ges
117 byte 3: 0 y9 y8 y7 1 M R L
118 byte 4: 0 y6 y5 y4 y3 y2 y1 y0
119 byte 5: 0 z6 z5 z4 z3 z2 z1 z0
121 Protocol Version 2 DualPoint devices send standard PS/2 mouse packets for
122 the DualPoint Stick. The M, R and L bits signal the combined status of both
123 the pointingstick and touchpad buttons, except for Dell dualpoint devices
124 where the pointingstick buttons get reported separately in the PSM, PSR
125 and PSL bits.
127 Dualpoint device -- interleaved packet format
128 ---------------------------------------------
130 byte 0: 1 1 0 0 1 1 1 1
131 byte 1: 0 x6 x5 x4 x3 x2 x1 x0
132 byte 2: 0 x10 x9 x8 x7 0 fin ges
133 byte 3: 0 0 YSGN XSGN 1 1 1 1
134 byte 4: X7 X6 X5 X4 X3 X2 X1 X0
135 byte 5: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0
136 byte 6: 0 y9 y8 y7 1 m r l
137 byte 7: 0 y6 y5 y4 y3 y2 y1 y0
138 byte 8: 0 z6 z5 z4 z3 z2 z1 z0
140 Devices which use the interleaving format normally send standard PS/2 mouse
141 packets for the DualPoint Stick + ALPS Absolute Mode packets for the
142 touchpad, switching to the interleaved packet format when both the stick and
143 the touchpad are used at the same time.
145 ALPS Absolute Mode - Protocol Version 3
146 ---------------------------------------
148 ALPS protocol version 3 has three different packet formats. The first two are
149 associated with touchpad events, and the third is associated with trackstick
150 events.
152 The first type is the touchpad position packet.
154 byte 0: 1 ? x1 x0 1 1 1 1
155 byte 1: 0 x10 x9 x8 x7 x6 x5 x4
156 byte 2: 0 y10 y9 y8 y7 y6 y5 y4
157 byte 3: 0 M R L 1 m r l
158 byte 4: 0 mt x3 x2 y3 y2 y1 y0
159 byte 5: 0 z6 z5 z4 z3 z2 z1 z0
161 Note that for some devices the trackstick buttons are reported in this packet,
162 and on others it is reported in the trackstick packets.
164 The second packet type contains bitmaps representing the x and y axes. In the
165 bitmaps a given bit is set if there is a finger covering that position on the
166 given axis. Thus the bitmap packet can be used for low-resolution multi-touch
167 data, although finger tracking is not possible. This packet also encodes the
168 number of contacts (f1 and f0 in the table below).
170 byte 0: 1 1 x1 x0 1 1 1 1
171 byte 1: 0 x8 x7 x6 x5 x4 x3 x2
172 byte 2: 0 y7 y6 y5 y4 y3 y2 y1
173 byte 3: 0 y10 y9 y8 1 1 1 1
174 byte 4: 0 x14 x13 x12 x11 x10 x9 y0
175 byte 5: 0 1 ? ? ? ? f1 f0
177 This packet only appears after a position packet with the mt bit set, and
178 usually only appears when there are two or more contacts (although
179 occasionally it's seen with only a single contact).
181 The final v3 packet type is the trackstick packet.
183 byte 0: 1 1 x7 y7 1 1 1 1
184 byte 1: 0 x6 x5 x4 x3 x2 x1 x0
185 byte 2: 0 y6 y5 y4 y3 y2 y1 y0
186 byte 3: 0 1 0 0 1 0 0 0
187 byte 4: 0 z4 z3 z2 z1 z0 ? ?
188 byte 5: 0 0 1 1 1 1 1 1
190 ALPS Absolute Mode - Protocol Version 4
191 ---------------------------------------
193 Protocol version 4 has an 8-byte packet format.
195 byte 0: 1 ? x1 x0 1 1 1 1
196 byte 1: 0 x10 x9 x8 x7 x6 x5 x4
197 byte 2: 0 y10 y9 y8 y7 y6 y5 y4
198 byte 3: 0 1 x3 x2 y3 y2 y1 y0
199 byte 4: 0 ? ? ? 1 ? r l
200 byte 5: 0 z6 z5 z4 z3 z2 z1 z0
201 byte 6: bitmap data (described below)
202 byte 7: bitmap data (described below)
204 The last two bytes represent a partial bitmap packet, with 3 full packets
205 required to construct a complete bitmap packet. Once assembled, the 6-byte
206 bitmap packet has the following format:
208 byte 0: 0 1 x7 x6 x5 x4 x3 x2
209 byte 1: 0 x1 x0 y4 y3 y2 y1 y0
210 byte 2: 0 0 ? x14 x13 x12 x11 x10
211 byte 3: 0 x9 x8 y9 y8 y7 y6 y5
212 byte 4: 0 0 0 0 0 0 0 0
213 byte 5: 0 0 0 0 0 0 0 y10
215 There are several things worth noting here.
217 1) In the bitmap data, bit 6 of byte 0 serves as a sync byte to
218 identify the first fragment of a bitmap packet.
220 2) The bitmaps represent the same data as in the v3 bitmap packets, although
221 the packet layout is different.
223 3) There doesn't seem to be a count of the contact points anywhere in the v4
224 protocol packets. Deriving a count of contact points must be done by
225 analyzing the bitmaps.
227 4) There is a 3 to 1 ratio of position packets to bitmap packets. Therefore
228 MT position can only be updated for every third ST position update, and
229 the count of contact points can only be updated every third packet as
230 well.
232 So far no v4 devices with tracksticks have been encountered.
234 ALPS Absolute Mode - Protocol Version 5
235 ---------------------------------------
236 This is basically Protocol Version 3 but with different logic for packet
237 decode. It uses the same alps_process_touchpad_packet_v3 call with a
238 specialized decode_fields function pointer to correctly interpret the
239 packets. This appears to only be used by the Dolphin devices.
241 For single-touch, the 6-byte packet format is:
243 byte 0: 1 1 0 0 1 0 0 0
244 byte 1: 0 x6 x5 x4 x3 x2 x1 x0
245 byte 2: 0 y6 y5 y4 y3 y2 y1 y0
246 byte 3: 0 M R L 1 m r l
247 byte 4: y10 y9 y8 y7 x10 x9 x8 x7
248 byte 5: 0 z6 z5 z4 z3 z2 z1 z0
250 For mt, the format is:
252 byte 0: 1 1 1 n3 1 n2 n1 x24
253 byte 1: 1 y7 y6 y5 y4 y3 y2 y1
254 byte 2: ? x2 x1 y12 y11 y10 y9 y8
255 byte 3: 0 x23 x22 x21 x20 x19 x18 x17
256 byte 4: 0 x9 x8 x7 x6 x5 x4 x3
257 byte 5: 0 x16 x15 x14 x13 x12 x11 x10
259 ALPS Absolute Mode - Protocol Version 6
260 ---------------------------------------
262 For trackstick packet, the format is:
264 byte 0: 1 1 1 1 1 1 1 1
265 byte 1: 0 X6 X5 X4 X3 X2 X1 X0
266 byte 2: 0 Y6 Y5 Y4 Y3 Y2 Y1 Y0
267 byte 3: ? Y7 X7 ? ? M R L
268 byte 4: Z7 Z6 Z5 Z4 Z3 Z2 Z1 Z0
269 byte 5: 0 1 1 1 1 1 1 1
271 For touchpad packet, the format is:
273 byte 0: 1 1 1 1 1 1 1 1
274 byte 1: 0 0 0 0 x3 x2 x1 x0
275 byte 2: 0 0 0 0 y3 y2 y1 y0
276 byte 3: ? x7 x6 x5 x4 ? r l
277 byte 4: ? y7 y6 y5 y4 ? ? ?
278 byte 5: z7 z6 z5 z4 z3 z2 z1 z0
280 (v6 touchpad does not have middle button)
282 ALPS Absolute Mode - Protocol Version 7
283 ---------------------------------------
285 For trackstick packet, the format is:
287 byte 0: 0 1 0 0 1 0 0 0
288 byte 1: 1 1 * * 1 M R L
289 byte 2: X7 1 X5 X4 X3 X2 X1 X0
290 byte 3: Z6 1 Y6 X6 1 Y2 Y1 Y0
291 byte 4: Y7 0 Y5 Y4 Y3 1 1 0
292 byte 5: T&P 0 Z5 Z4 Z3 Z2 Z1 Z0
294 For touchpad packet, the format is:
296 packet-fmt b7 b6 b5 b4 b3 b2 b1 b0
297 byte 0: TWO & MULTI L 1 R M 1 Y0-2 Y0-1 Y0-0
298 byte 0: NEW L 1 X1-5 1 1 Y0-2 Y0-1 Y0-0
299 byte 1: Y0-10 Y0-9 Y0-8 Y0-7 Y0-6 Y0-5 Y0-4 Y0-3
300 byte 2: X0-11 1 X0-10 X0-9 X0-8 X0-7 X0-6 X0-5
301 byte 3: X1-11 1 X0-4 X0-3 1 X0-2 X0-1 X0-0
302 byte 4: TWO X1-10 TWO X1-9 X1-8 X1-7 X1-6 X1-5 X1-4
303 byte 4: MULTI X1-10 TWO X1-9 X1-8 X1-7 X1-6 Y1-5 1
304 byte 4: NEW X1-10 TWO X1-9 X1-8 X1-7 X1-6 0 0
305 byte 5: TWO & NEW Y1-10 0 Y1-9 Y1-8 Y1-7 Y1-6 Y1-5 Y1-4
306 byte 5: MULTI Y1-10 0 Y1-9 Y1-8 Y1-7 Y1-6 F-1 F-0
308 L: Left button
309 R / M: Non-clickpads: Right / Middle button
310 Clickpads: When > 2 fingers are down, and some fingers
311 are in the button area, then the 2 coordinates reported
312 are for fingers outside the button area and these report
313 extra fingers being present in the right / left button
314 area. Note these fingers are not added to the F field!
315 so if a TWO packet is received and R = 1 then there are
316 3 fingers down, etc.
317 TWO: 1: Two touches present, byte 0/4/5 are in TWO fmt
318 0: If byte 4 bit 0 is 1, then byte 0/4/5 are in MULTI fmt
319 otherwise byte 0 bit 4 must be set and byte 0/4/5 are
320 in NEW fmt
321 F: Number of fingers - 3, 0 means 3 fingers, 1 means 4 ...